Novel Quinolone substituted 1,3,4-oxadiazole derivatives: Design, synthesis, antimicrobial and anti-inflammatory potential

Novel Quinolone substituted 1,3,4-oxadiazole derivatives: Design, synthesis, antimicrobial and anti-inflammatory potential | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Novel Quinolone substituted 1,3,4-oxadiazole derivatives: Design, synthesis, antimicrobial and anti-inflammatory potential Vishal Sharma, Rina Das, Dinesh Kumar Mehta, Diksha Sharma This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4334362/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 03 Aug, 2024 Read the published version in Molecular Diversity → Version 1 posted 4 You are reading this latest preprint version Abstract A novel series of quinolone-substituted 1,3,4-oxadiazole derivatives 4(a-l) have been designed and synthesized. The target compounds were investigated for their antibacterial activity against gram positive ( Staphylococcus aureus , ATCC 25923, Enterococcus faecalis, ATCC 29212) and gram negative bacterium ( Escherichia coli , ATCC 25922, Pseudomonas aeruginosa , ATCC 27853) for antifungal activity using candida albicans (ATCC 10231) and anti-inflammatory activity as COX-II inhibitors, respectively. The 1,3,4-oxadiazole functionality was introduced at C-6 position of pipemidic acid derivatives. The structure of synthesized derivatives was confirmed by IR, 1 H NMR and Mass spectrometry techniques. The quinolone (pipemidic acid)-oxadiazole hybrid derivatives were found to be effective against bacterial strains. When compared to ciprofloxacin (MIC 16 µg/mL), the compounds under consideration ( 4f, 4h, and 4k ) showed potent antibacterial activity against all bacterial strains except Enterococcus faecalis , with MICs of 8 µg/mL. On the other hand, synthesized target compounds (4a–l) did not respond well against the Candida albicans fungal strain. The compound (4k) represents the high % inhibition against COX-II . The compounds (4f, 4h & 4k) exhibited the highest hydrogen bonding interaction with ARG57, ARG72, ARG78, LEU54 and MET16 target residues with a binding energy of -8.4, -8.6 & -8.5 kcal/mol into the active pocket of DNA gyrase enzyme respectively even better in comparison to reference ligands. Based on the docking study, the quinolone (pipemidic acid) oxadiazole hybrid structural ligands exhibited strong interaction at binding pockets of DNA gyrase enzyme. Quinolone Pipemidic acid 1 3 4 oxadiazole Antimicrobial Anti-inflammatory Binding energy Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Highlights Quinolone hybrid oxadiazole derivatives were docked into active site of gram +ve, gram –ve and COX-II target sites. Most prominent 12 derivatives were synthesized based on the best binding score. Compounds 4f, 4h & 4k showed potent antibacterial activity against Staphylococcus aureus , Escherichia coli and Pseudomonas aeruginosa bacterial strains. Compound 4K showed maximum anti-inflammatory activity. Introduction Despite the fact that microorganisms are vital to the ecosystem's operation, they pose a grave threat to human life and health. Antibiotic resistance is a growing hazard to humanity. At least 50,000 people die daily from drug-related illnesses in developed and developing nations, according to WHO figures. The current situation of available medications can be attributed to the extensive utilization of existing drugs, including their limited antibacterial spectrum, hypersensitivity, and antimicrobial resistance (AMR) as undesirable side effects [ 1 ]. The persistent severity of antibiotic resistance has led to extensive research in the development of more bioactive molecules. To address the challenges associated with microbial resistance, there is an urgent need for thorough scientific investigation and research to develop safe and efficient antimicrobial drugs. Undoubtedly, significant attention has been drawn to nitrogen-containing heterocyclic aromatic molecules over the past two centuries, such as the quinolone moiety, to create novel synthetic agents with potent antimicrobial properties [ 2 ]. Quinolones are the most widely used antibacterial agents due to their bioavailability and extensive use. Its antibacterial activity comes from interfering with topoisomerase II (DNA gyrase and IV), which are critical for bacterial DNA synthesis and replication. [ 3 ]. Based on a literature review, quinolones demonstrated several biological profiles in addition to their ability to fight bacteria like anti-inflammatory [ 4 – 5 ], anti-HCV [6], anti-cancer [ 7 – 11 ], anti-malarial [ 12 – 13 ], anti-HIV [ 14 – 15 ], and antidepressant activities [ 16 ]. Many quinolone derivatives are used in clinics as antibacterial drugs, such as MCB3837, MCB3681, CBR-2092 (rifamycin-quinolone conjugate), and Ro-23-9424 (in phase II clinical study) to treat a variety of infections [ 17 – 19 ]. The antibacterial potential of pipemidic acid and quinolone is just one of many therapeutic benefits [ 20 ]. The incorporation of the 1,3,4-oxadiazole motif into the core structure of pipemidic acid has attracted significant interest and is widely regarded as a prominent approach to address resistance-related problems [ 21 ]. The structural alteration of the quinolone core skeleton at the C-6 position has been regarded to be an efficient strategy to circumvent antibiotic resistance issues and preserve inhibitory efficacy in response to multidrug-resistant microbes. Computer modelling tools simplify understanding the binding and important active site residues of unidentified target molecules. Structure and ligand-based drug design predict better ligands to strengthen interaction and increase target site potency [ 22 ]. In the present investigation, we used comprehensive molecular modeling to investigate the binding manner, and essential active interactions and estimate their binding affinity of the ligands using different PDB ids of DNA topoisomerases as the target. Furthermore, structural alteration of the quinolone skeleton at the C-6 position may avoid antibiotic resistance processes while maintaining inhibitory activity against multidrug-resistant bacteria [ 23 ]. We have great interest in integrating the oxadiazole motif to pipemidic acid quinolone at the C-6 position to develop new antibacterial molecules. Pipemidic acid, with the introduction of oxadiazole moiety at C-6 position exhibited potent bacterial action against resistance microbes [ 24 ]. From perusal of the literature, we targeted the design, synthesis and biological evaluation of novel quinolone containing oxadiazole derivatives for their antimicrobial and anti-inflammatory potential. Results and discussion Our study commenced by synthesizing the title quinolone derivatives (4a-l) in three steps is outlined in Scheme-1. In the step-I, the synthesis of ethyl 8-ethyl-5-oxo-2-(piperazin-1-yl)-5, 8-dihydropyrido[2,3- d ]pyrimidine-6-carboxylate (2) was done by esterification of pipemidic acid (1) . In step-II ester (2) was further treated with hydrazine hydrate to afford the corresponding 8-ethyl-5-oxo-2-(piperazin-1-yl)-5,8-dihydropyrido[2,3- d ]pyrimidine-6-carbohydrazide (3) in 70-80% yield. Step-III involves synthesis of title pipemidic acid containing oxadiazole derivatives (4) by refluxing equimolar mixture (1:1) of hydrazide (3) with different aromatic carboxylic acid (I-XII) in the presence of phosphorous oxychloride for 2–3 h (Scheme-1). The completion of the reaction was monitored by TLC using chloroform: ethanol (10:1) solvent system. The synthesized derivatives (figure 1) were purified by column chromatographic technique. The structures of synthesized pipemidic acid hybrid derivatives 4(a-l) were confirmed by IR, NMR, Mass spectroscopy and elemental analysis. The functional group identification was done using FTIR based on characteristic absorption bands corresponding to –NH, -C=O, -CH aromatic & -CH aliphatic and –C=N groups. FTIR spectra of all synthesized pipemidic acid derivatives reported –NH stretching in the range of 3340-3500 cm -1 . The vibrational frequency at 1617-1720 cm -1 showed the presence of carbonyl moiety in synthesized derivatives. Other characteristic peaks for –CH aliphatic, -CH aromatic and –C=N were reported at 2914-2927 cm -1 , 3100-3250 cm -1 and 1383-1477 cm -1 respectively. Furthermore, NMR spectra of synthesized analogues showed peak at δ 1.1-1.4 ppm and doublet signal for aromatic hydrogens at δ 7.0-8.0 ppm. The signal for –CH 2 of piperazine ring showed in between δ 2.0-3.0 ppm and singlet peak for C-4 and C-7 hydrogen of pyridopyrimidine ring in pipemidic acid derivatives at δ 7.4-7.7 ppm. MS spectra depicted specific molecular ion (M + ) peak correlated to the molecular weight of synthesized compounds. Molecular Docking Studies In this study, the three-dimensional crystal structure of quinolones with DNA gyrase (topoisomerase II) from gram-positive and gram-negative bacteria and COX-II was employed. For docking study, library of fifty molecules was docked into the binding site of receptor using Autodock 4.2. In this investigation, the docking score and H-bond interactions of synthesized derivatives were computed and shown as dotted green color lines. Out of all screened compounds, twelve derivatives were estimated to be having best binding affinity in terms of kcal/mol with common residues (ARG72, ARG78, ARG57, LYS32, SER49, LEU54, ILE94, ALA6, THR100, PHE31, MET16) and exhibited confirmed free energy of binding ranged from -4.5 to -8.6 kcal/mol, as shown in figures (2-11). Compound 4f, 4h & 4k estimated best free energy of binding, -8.4, -8.6 & -8.5 kcal/mol into the binding pocket of DNA gyrase enzyme respectively even better in comparison to reference ligands, as represented in figure 2, 5 & 8 and exhibited highest hydrogen bonding interaction with amino acids ARG57, ARG72 & ARG78. Furthermore, compound 4K confirmed to be having significant docking score -8.20 kcal/mol in protein target (5ikr) of COX-II and hydrogen bonding interaction with amino acids TYR355 & ARG120. The docked structures of 4f, 4h & 4k with these target sites confirmed that the electron withdrawing & donating functionality at C-6 position of pipemidic acid showed significant interactions with different amino acid residues at target site. The binding score of each of the ligand library against the DNA gyrase is tabulated in Table. 1. Table 1: Docking results of synthesized quinolone substituted 1,3,4-oxadiazole derivatives S. No. Compound Docking Score (kcal/mol)) Streptococcus aureus(+ve) 2w9s Enterococcus faecalis(+ve) 1yzf E. coli (-ve) 6cqa Pseudomonas aeruginosa (-ve) 6m1j COX-II (5ikr) 1 4a -7.03 -7.09 -8.30 -7.63 -6.44 2 4b -4.48 -6.48 -7.90 -7.13 -7.56 3 4c -5.60 -6.14 -7.76 -8.05 -6.86 4 4d -4.15 -5.80 -7.41 -7.71 -6.34 5 4e -4.36 -6.36 -7.21 -7.79 -6.87 6 4f -8.40 -6.17 -8.25 -8.22 -8.05 7 4g -6.15 -6.23 -7.76 -8.09 -5.97 8 4h -8.63 -6.27 -8.16 -8.09 -8.00 9 4i -4.21 -6.11 -7.66 -6.83 -4.67 10 4j -4.23 -6.82 -7.86 -6.23 -6.44 11. 4k -8.56 -6.23 -8.07 -8.20 -8.20 12. 4l -5.11 -6.46 -7.95 -8.14 -7.76 13. Ciprofloxacin/Naproxen * -7.21 -5.62 -7.64 -7.86 -7.75* 14. Pipemidic Acid -6.71 -6.40 -7.45 -7.87 -6.67 BIOLOGICAL ACTIVITY Screening of antibacterial and antifungal activities All quinolone substituted 1,3,4-oxadiazole derivatives (4a-l) were tested for antibacterial and antifungal activity to determine their MIC values against gram-positive ( Staphylococcus aureus & Enterococcus faecalis , gram-negative ( Escherichia coli & Pseudomonas aeruginosa and fungal strains. Pipemidic acid was employed as a positive control and ciprofloxacin (CIP) and fluconazole as standards (Table 2). SARAccording to the antibacterial data, newly synthesized compounds profoundly impact the antibacterial profile of Gram-positive and negative bacterial strains. The compounds exhibited a moderate activity against E. faecalis and a considerable inhibitory effect against S. aureus , E. coli , and P. aeruginosa . Out of the tested derivatives, compounds 4i & 4j were found to be least active against gram positive and gram negative bacteria with MIC value of 64-512 µg/mL; however compounds 4a-4e, 4g & 4i exhibited moderate activity against gram positive & negative strain. These biological data exhibited an unexpected structure-activity relationship (SAR), showing that pipemidic acid's antibacterial potency was greatly impacted by the sixth carbon atom substitution. Specifically, the presence of electron-donating and releasing functionality with phenyl oxadiazole moiety at C-6 position considered effective for antibacterial activity. On the other hand, it has been confirmed that the pipemidic acid derivatives (4a–l) lacked antifungal efficacy against the candida albicans fungal strain. Anti-inflammatory activity The anti-inflammatory effect of synthesised derivatives (4a-l) was tested in rats with carrageenan-induced paw oedema and naproxen as a reference medication. In Table 2, results are shown as mean ± S.D. One-way ANOVA and Tukey's test were used to compare control and treatment groups for statistical significance. The test derivatives significantly reduced the volume of the paw oedema when given one hour before the carrageenan injection at a dose of 50 mg/kg body weight. Maximum anti-inflammatory action is conferred by compound 4k, which has a 3-methylphenyl oxadiazole substitution on the C-6 position of pipemidic core structure. Moderate anti-inflammatory activity is conferred by compounds 4f & 4h, which have 2-fluorophenyl and 2-chlorophenyl oxadiazole substitution. Paw oedema volume and % oedema inhibition values were strongly inhibited by the presence of methyl functionality as an electron-releasing group in the meta position of the phenyl ring linked with oxadiazole moiety. These values were also extremely near to those of the standard compound. Table: 2 MICs of synthesized quinolone substituted 1,3,4-oxadiazole derivatives(4a-l) Compound Staphylococcus aureus (ATCC 25923) Enterococcus faecalis (ATCC 29212) Escherichia coli (ATCC 25922) Pseudomonas aeruginosa (ATCC 27853) Candida albicans (ATCC 10231) 4a 16 16 8 16 - 4b 512 64 16 16 - 4c 128 64 16 8 - 4d 512 256 16 16 - 4e 256 64 16 16 >1024 4f 8 64 8 8 - 4g 128 64 16 8 - 4h 8 64 8 8 - 4i 512 128 64 128 >1024 4j 512 128 64 128 - 4k 8 64 8 8 - 4l 256 64 16 8 - PA 16 16 16 16 - CIP/Fluconazole* 0.5 0.5 0.125 0.125 2* PA: Pipemidic acid; CIP: Ciprofloxacin. All the experiments were performed in triplicates (n=3), MIC represented in µg/ml, “-” no activity observed Anti-inflammatory activity: Table: 3 Effect of synthesized derivatives (4a-l) on carrageenan-induced paw oedema in rats Compounds Paw volume (ml) (mean±SEM) 0 hr 1 hr 2 hr 3 hr 4 hr 4a 0.97±0.01 1.11±0.02 1.19±0.03 1.27±0.02 1.33±0.03 4b 0.90±0.02 1.05±0.01 1.09±0.01 b* 1.12±0.02 b* 1.23±0.02 b* 4c 0.90±0.02 0.99±0.00 b* 1.02±0.02 b* 1.15±0.01 b* 1.20±0.02 b* 4d 0.97±0.02 1.15±0.01 1.10±0.02 b* 1.15±0.00 b* 1.29±0.03 b* 4e 0.86±0.02 0.97±0.01 b* 1.08±0.02 b* 1.15±0.02 b* 1.23±0.03 b* 4f 0.92±0.03 1.06±0.01 b* 0.96±0.02 b** 0.85±0.01 b*** 0.86±0.02 b*** 4g 0.93±0.03 1.07±0.01 b* 1.25±0.02 1.29±0.01 1.20±0.02 b* 4h 0.88±0.03 1.07±0.01 b* 0.95±0.01 b** 0.83±0.01 b*** 0.86±0.02 b*** 4i 0.89±0.01 0.98±0.00 b* 1.23±0.02 1.25±0.02 1.24±0.01 b* 4j 0.98±0.01 1.18±0.03 1.21±0.02 1.28±0.02 1.31±0.03 4k 0.90±0.02 1.06±0.02 0.97±0.02 b*** 0.86±0.01 b*** 0.82±0.01 b*** 4l 0.90±0.02 1.07±0.01 1.08±0.02 b** 0.92±0.03 b*** 1.11±0.03 Normal 0.81±0.01 0.81±0.01 0.82±0.01 0.82±0.01 0.8±0.02 Positive control 0.98±0.01 1.16±0.02 a** 1.26±0.02 a*** 1.31±0.02 a*** 1.4±0.05 a*** Std 0.88±0.00 0.98±0.004 b** 0.93±0.00 b** 0.84±0.01 b*** 0.8±0.02 b*** All the values represent means of two determinations; p<0.05=*, p<0.01=**, p<0.001=*** Percentage inhibition: Table: 4 Effect of synthesized derivatives (4a-l) on carrageenan induced paw oedema in rats S.No. Compounds % inhibition 0 hr 1 hr 2 hr 3 hr 4 hr 1. 4a -1 21 32 34 43 2. 4b 6 26 40 46 50 3. 4c 6 32 46 43 52 4. 4d -1 18 39 43 45 5. 4e 11 33 41 43 50 6. 4f 4 25 50 66 77 7. 4g 3 25 27 32 52 8. 4h 8 24 51 68 77 9. 4i 7 32 29 36 49 10. 4j -2 15 30 33 44 11. 4k 7 25 50 65 80 12. 4l 7 24 41 61 59 13. Naproxen 8 32 53 67 79 Material & Method Only analytical-grade chemicals and solvents were utilised. All chemicals came from Sigma-Aldrich, India. A UV-lit spot on pre-coated silica gel plates (TLC silica gel) assessed the purity of all chemicals. In a chloroform: ethanol (10:1) solvent solution, TLC monitored reaction completion. The Stuart SMP30 melting point device recorded uncorrected melting points. The elemental analyses were recorded on Perkin-Elmer 240Bs. Chemical shifts were measured in parts per million (δ) units using tetramethylsilane as an internal reference, using SHIMADZU (Japan) IR and Bruker Advance Neo 500 MHz NMR spectrophotometers. Mass spectrum data were collected using synapt-XS#DBA064 (Water Corporation). General procedure for the synthesis of 8-ethyl-5-oxo-2-(piperazin-1-yl)-5,8-dihydropyrido[2,3- d ]pyrimidine-6-carboxylate (2) A mixture of compound (1) (1.5 g, 0.0051mol) in ethanol (20 ml) was refluxed in the presence of conc. sulphuric acid (1 ml) for 7 hours. After the reaction was complete, the mixture was carefully poured into ice water. To neutralise the excess acid, a sodium bicarbonate solution was added. The resulting solid was then filtered and washed with water. This process yielded white crystals, with a melting point of 236-238°C, and a yield of 73%. Synthesis of 8-ethyl-5-oxo-2-(piperazin-1-yl)-5,8-dihydropyrido[2,3- d ]pyrimidine-6-carbohydrazide (3) A mixture of comnpound (2) 0.3 g (0.0015 mol) and hydrazine hydrate (5 ml) in methanol (6 ml) was refluxed for 7 hours. Then reaction mixture was concentrated and left for cool. Finally, ethanol was used to filter and recrystallize the off-white solid into white crystals (3). Yield: 67%, m.p. 241-244˯C. TLC methanol: chloroform (7:3). Synthesis of 8-ethyl-2-(piperazin-1-yl)-6-(1,3,4-oxadiazol-2-yl)pyrido[2,3-d]pyrimidin-5(8 H )-one (4) An equimolar concentration of compound 3 (0.211g, 0.01mol) and 4-nitro benzoic acid (0.111g, 0.01 mol) was refluxed with phosphorous oxychloride (4ml). For 2 hours, the reaction mixture was refluxed at 100˚C. The surplus POCl3 was concentrated under high vacuum after cooling the reaction mixture to room temperature. TLC analysed the reaction. Also, surplus POCl3 was distilled under lower pressure. The reaction material was agitated and placed into ice-cold water after cooling. After separation, the solid was filtered and washed with sodium bicarbonate and water. Recrystallizing with ethanol yielded dark crystalline solids of the final compound (4). 8-ethyl-6-(5-(4-nitrophenyl)-1,3,4-oxadiazol-2-yl)-2-(piperazin-1-yl)pyrido[2,3-d]pyrimidin-5(8H)-one (4a) Reddish brown color solid, yield (66%), m.p. 238-240 ֯ C. IR (KBr, cm -1 ): 3432.27 (NH str): 3113.61(-CH str aromatic): 1694.75 (C=O str): 1610.52 (C=C str): 1525 (NO 2 str): 1434.72 (C=N str): 1108.25 (C-O-C str): 1257.60 (C-N str): 2923.71 (C-H aliphatic str); 1 H NMR (500 MHz, DMSO) δ ppm: 8.1, 8.3 (m, 4H, aromatic hydrogen), 1.22 (t, 3H, -CH 3 ), 1.45 (NH, piperazine ring), 7.7 (s, 1H, CH at C-7), 2.5 & 3.3 (m, 8H,-CH 2 piperazine ring), 4.1 (m, -CH 2 ethyl), 7.2 (s, CH at C-4), TOF MS ES + (m/z): 448 M + , other fragments are 326 m + , 258 m + ; CHN Analysis calcted (%) for C 21 H 19 N 8 O 4 : C, 56.25; H, 4.50; N, 24.99 found: C, 56.55; H, 4.80; N, 24.59. 6-(5-(4-chlorophenyl)-1,3,4-oxadiazol-2-yl)-8-ethyl-2-(piperazin-1-yl)pyrido[2,3-d]pyrimidin-5(8H)-one (4b) Dark brown color solid, yield (68%), m.p. 253-255 ֯ C; IR (KBr, cm -1 ): 3427.52 (NH str): 3243.95 (-CH str aromatic): 1717.26 (C=O str): 1636.18 (C=C str): 738.40 (C-Cl str): 1477.23 (C=N str): 1091.32 (C-O-C str): 1385.55 (C-N str): 2926.69 (C-H aliphatic str); 1 H NMR (500 MHz, DMSO) δ ppm: 7.9, 7.2 (m, 4H, aromatic hydrogen), 1.4 (t, 3H, -CH 3 ), 1.22 (NH piperazine ring), 7.5 (s, 1H, CH at C-4), 2.5, 3.4 (m, 8H, -CH 2 piperazine ring), 4.4 (m, -CH 2 ethyl), 8.3 (s, CH at C-7), TOF MS ES + 437 M + , other fragments are 326 m + , 293 m + , 258 m + ; CHN Analysis calcted (%) for C 21 H 19 N 7 O 2 Cl: C, 57.60; H, 4.60; N, 22.39 found: C, 57.20; H, 4.20; N, 21.45. 8-ethyl-6-(5-(4-hydroxyphenyl)-1,3,4-oxadiazol-2-yl)-2-(piperazin-1-yl)pyrido[2,3-d]pyrimidin-5(8H)-one (4c) Dark brown color solid, yield (65%), m.p. 258-260 ֯ C; IR (KBr, cm -1 ): 3550.90 (C-OH): 3474.36 (NH str): 3167.16 (-CH str aromatic): 1636.66 (C=C str): 1617.59 (C=O str): 1449.67 (C=N str): 1061.38 (C-O-C str): 1383.15 (C-N str): 2926.97 (C-H aliphatic str); 1 H NMR (500 MHz, DMSO) δ ppm: 7.8, 6.5 (m, 4H, aromatic hydrogen), 9.2 (s, -OH), 1.4 (t, 3H, -CH 3 ), 1.1 (NH piperazine ring), 7.4 (s, 1H, CH at C-4), 2.40, 3.46 (m, 8H, -CH 2 piperazine ring), 7.1 (s, CH at C-7), 4.4 (m, -CH 2 ethyl), TOF MS ES + 420 M + , other fragments are 326 m + , 258 m + ; CHN Analysis calcted (%) for C 21 H 20 N 7 O 3 : C, 60.13; H, 5.05; N, 23.38 found: C, 60.43; H, 5.25; N, 23.18. 6-(5-(4-aminophenyl)-1,3,4-oxadiazol-2-yl)-8-ethyl-2-(piperazin-1-yl)pyrido[2,3-d]pyrimidin-5(8H)-one (4d) Reddish brown color solid, yield (63%), m.p. 264-267 ֯ C; IR (KBr, cm -1 ): 3459.34 (C-NH 2 ): 3416.25 (NH str): 3127.17 (-CH str aromatic): 1620.22 (C=O str): 1633.97 (C=C str): 1383.39 (C=N str): 1089.15 (C-O-C str): 1383.39 (C-N str): 2923.58 (C-H aliphatic str); 1 H NMR (500 MHz, DMSO) δ ppm: 7.8, 6.6 (m, 4H, aromatic hydrogen), 5.5 (s, -NH 2 ), 1.53 (t, 3H, -CH 3 ), 1.27 (NH piperazine ring), 2.5, 3.4 (m, 8H, -CH 2 piperazine ring), 7.8 (s, -CH at C-4), 7.4 (s, -CH at C-7), 4.1 (m, -CH 2 ethyl), TOF MS ES + 418 M + , other fragments are 327 m + , 257 m + ; CHN Analysis calcted (%) for C 21 H 21 N 8 O 2 : C, 60.28; H, 5.30; N, 26.78 found: C, 60.48; H, 5.50; N, 26.38. 8-ethyl-6-(5-(4-methoxyphenyl)-1,3,4-oxadiazol-2-yl)-2-(piperazin-1-yl)pyrido[2,3-d]pyrimidin-5(8H)-one (4e) Light brown color solid, yield (60%), m.p. 248-252 ֯ C; IR (KBr, cm -1 ): 3433.55 (NH str): 2925 (aliphatic, C-H), 1113 (aliphatic C-O linkage) 3160.12 (-CH str aromatic): 1623.27 (C=C str): 1692.11 (C=O str): 1444.19 (C=N str): 1062.73 (C-O-C str): 1382.77 (C-N str): 2852.74 (C-H aliphatic str); 1 H NMR (500 MHz, DMSO) δ ppm: 8.1, 7.0 (m, 4H, aromatic hydrogen), 3.8 (s, 3H, O-CH 3 ), 1.4 (t, 3H, -CH 3 ), 1.2 (NH piperazine ring), 3.2, 2.5 (m, 8H, -CH 2 piperazine), 7.4 (s, -CH at C-7), 4.3 (m, -CH 2 ethyl), 7.7 (s, -CH at C-4), TOF MS ES + 434 M + , other fragments are 418 m + , 326 m + , 284 m + ; CHN Analysis calcted (%) for C 22 H 22 N 7 O 3 : C, 60.96; H, 5.35; N, 22.62; found: C, 60.45; H, 5.65; N, 22.12. 8-ethyl-6-(5-(2-fluorophenyl)-1,3,4-oxadiazol-2-yl)-2-(piperazin-1-yl)pyrido[2,3-d]pyrimidin-5(8H)-one (4f) Reddish brown color solid, yield (62%), m.p. 253-256 ֯ C; IR (KBr, cm -1 ): 3360.50 (NH str): 3243.95 (-CH str aromatic): 1720.16 (C=O str): 1635.15 (C=C str): 1220.12 (C-F str): 1470.23 (C=N str): 1110.32 (C-O-C str): 1385.55 (C-N str): 2914.64 (C-H aliphatic str); 1 H NMR (500 MHz, DMSO) δ ppm: 8.3, 7.9, 7.3 (m, 4H, aromatic hydrogen), 1.4 (t, 3H, -CH 3 ), 1.1 (NH piperazine ring), 7.7 (s, 1H, -CH at C-4), 2.5, 3.2 (m, 8H, -CH 2 piperazine ring), 7.5 (s, -CH at C-7), 4.1 (m, -CH 2 ethyl), TOF MS ES + 420 M + , other fragments are 327 m + , 258 m + ; CHN Analysis calcted (%) for C 21 H 19 N 7 O 2 F: C, 59.85; H, 4.78; N, 23.27 found: C, 59.65; H, 4.28; N, 23.17. 8-ethyl-6-(5-(4-fluorophenyl)-1,3,4-oxadiazol-2-yl)-2-(piperazin-1-yl)pyrido[2,3-d]pyrimidin-5(8H)-one (4g) Reddish brown color solid, yield (62%), m.p. 253-256 ֯ C; IR (KBr, cm -1 ): 3360.50 (NH str): 3243.95 (-CH str aromatic): 1720.16 (C=O str): 1635.15 (C=C str): 1220.12 (C-F str): 1470.23 (C=N str): 1110.32 (C-O-C str): 1385.55 (C-N str): 2916.64 (C-H aliphatic str); 1 H NMR (500 MHz, DMSO) δ ppm: 8.3, 7.3 (m, 4H, aromatic hydrogen), 1.43 (t, 3H, -CH 3 ), 1.15 (NH piperazine ring), 3.2, 2.5 (m, 8H, -CH 2 piperazine ring), 7.7 (s, -CH at C-4), 7.5 (s, -CH at C-7) TOF MS ES + 420 M + , other fragments are 327 m + , 304 m + , 258 m + ; CHN Analysis calcted (%) for C 21 H 19 N 7 O 2 F: C, 59.85; H, 4.78; N, 23.27 found: C, 58.23; H, 4.26; N. 22.98. 6-(5-(2-chlorophenyl)-1,3,4-oxadiazol-2-yl)-8-ethyl-2-(piperazin-1-yl)pyrido[2,3-d]pyrimidin-5(8H)-one (4h) Dark brown color solid, yield (68%), m.p. 253-255 ֯ C; IR (KBr, cm -1 ): 3427.52 (NH str): 3245.95 (-CH str aromatic): 1717.26 (C=O str): 1636.18 (C=C str): 738.40 (C-Cl str): 1477.23 (C=N str): 1091.32 (C-O-C str): 1385.55 (C-N str): 2925.59 (C-H aliphatic str); 1 H NMR (500 MHz, DMSO) δ ppm: 7.8, 7.7, 7.3 (m, 1H, aromatic hydrogen), 1.4 (t, 3H, -CH 3 ), 1.1 (NH piperazine ring), 3.2, 2.6 (m CH 2 piperazine), 7.5 (s, CH at C-7) 7.6 (s, CH at C-4), 4.1 (m, -CH 2 ethyl), TOF MS ES + 437 M + , other fragments are 326 m + , 293 m + , 258 m + ; CHN Analysis calcted (%) for C 21 H 19 N 7 O 2 Cl: C, 57.60; H, 4.60; N, 22.39 found: C, 57.45; H, 4.22; N, 22.64. 8-ethyl-2-(piperazin-1-yl)-6-(5-(3,4,5-trimethoxyphenyl)-1,3,4-oxadiazol-2-yl)pyrido[2,3-d]pyrimidin-5(8H­­­)-one (4i) Light brown color solid, yield (60%), m.p. 248-252 ֯ C; IR (KBr, cm -1 ): 3430.35 (NH str): 2925 (aliphatic, C-H), 2950 ( para -OCH 3 ), 2840.24, 2852.74 ( meta -OCH 3 ) 1113 (aliphatic C-O linkage) 3160.12 (-CH str aromatic): 1623.27 (C=C str): 1692.11 (C=O str): 1440.29 (C=N str): 1062.73 (C-O-C str): 1382.77 (C-N str): 2852.74 (C-H aliphatic str); 1 H NMR (500 MHz, DMSO) δ ppm: 7.3 (s, 2H, aromatic hydrogen), 3.7 (s, 3H, para , O-CH 3 ), 3.9 (s, 6H, meta , O-CH 3 ) 1.4 (t, 3H, -CH 3 ), 1.1 (NH piperazine ring), 3.2, 2.6 (m, 8H, -CH 2 piperazine), 7.5 (s, -CH at C-7), 4.2 (m, -CH 2 ethyl), 7.7 (s, -CH at C-4), TOF MS ES + 493 M + , other fragments are 448 m + , 326 m + , 284 m + ; CHN Analysis calcted (%) for C 24 H 22 N 7 O 5 : C, 58.41; H, 5.51; N, 19.87 found: C, 58.62; H, 5.44; N, 20.02. 6-(5-(2,4-dichlorophenyl)-1,3,4-oxadiazol-2-yl)-8-ethyl-2-(piperazin-1-yl)pyrido[2,3-d]pyrimidin-5(8H)-one (4j) Dark brown color solid, yield (68%), m.p. 253-255 ֯ C; IR (KBr, cm -1 ): 3427.52 (NH str): 3243.95 (-CH str aromatic): 1717.26 (C=O str): 1636.18 (C=C str): 740.26 (C-Cl str): 1477.23 (C=N str): 1091.32 (C-O-C str): 1385.55 (C-N str): 2926.69 (C-H aliphatic str); 1 H NMR (500 MHz, DMSO) δ ppm: 7.3, 7.7, 7.8 (s, 3H, aromatic hydrogen), 1.4 (t, 3H, -CH 3 ), 1.1 (NH piperazine ring), 7.5 (s, 1H, -CH at C-4), 2.6, 3.2 (m, 8H, -CH 2 piperazine ring), 4.1 (m, -CH 2 ethyl), 7.6 (s, -CH at C-7), TOF MS ES + 472 M + , other fragments are 400 m + , 326 m + , 293 m + , 258 m + ; CHN Analysis calcted (%) for C 21 H 18 N 7 O 2 Cl 2 : C, 53.40; H, 4.05; N, 20.76 found: C, 53.60; H, 4.15; N, 20.46. 8-ethyl-2-(piperazin-1-yl)-6-(5-(m-tolyl)-1,3,4-oxadiazol-2-yl)pyrido[2,3-d]pyrimidin-5(8H)-one (4k) Reddish brown color solid, yield (62%), m.p. 253-256 ֯ C; IR (KBr, cm -1 ): 3355.30 (NH str): 3250.90 (-CH str aromatic): 1718.26 (C=O str): 1635.15 (C=C str): 1220.12 (C-F str): 1465.26 (C=N str): 1110.32 (C-O-C str): 1385.55 (C-N str): 2920.14 (C-H aliphatic str); 1 H NMR (500 MHz, DMSO) δ ppm: 8.0, 7.7, 7.3, 7.0 (m, 4H, aromatic hydrogen), 1.4 (t, 3H, -CH 3 ), 1.1 (NH piperazine ring), 7.7 (s, 1H, -CH at C-4), 2.4 (s, 3H, phenyl –CH 3 ), 2.7, 3.2 (m, -CH 2 piperazine ring), 7.6 (s, -CH at C-7), 4.1 (m, -CH 2 ethyl), TOF MS ES + 417 M + , other fragments are 400 m + , 326 m + , 293 m + , 258 m + ; CHN Analysis calcted (%) for C 22 H 22 N 7 O 2 : C, 63.30; H, 5.55; N, 23.49; found: C, 63.25; H, 5.25; N, 23.69. 8-ethyl-2-(piperazin-1-yl)-6-(5-(p-tolyl)-1,3,4-oxadiazol-2-yl)pyrido[2,3-d]pyrimidin-5(8H)-one (4l) Reddish brown color solid, yield (62%), m.p. 260-262 ֯ C; IR (KBr, cm -1 ): 3390.20 (NH str): 3250.90 (-CH str aromatic): 1718.26 (C=O str): 1635.15 (C=C str): 1220.12 (C-F str): 1465.26 (C=N str): 1110.32 (C-O-C str): 1385.55 (C-N str): 2925.34 (C-H aliphatic str); 1 H NMR (500 MHz, DMSO) δ ppm: 8.0, 7.3 (m, 4H, aromatic hydrogen), 1.26 (t, 3H, -CH 3 ), 1.4 (NH piperazine ring), 7.7 (s, 1H, -CH at C-4), 2.4 (s, 3H, phenyl –CH 3 ), 2.7, 3.2 (m, 8H, -CH 2 piperazine ring), 7.5 (s, -CH at C-7), 4.1 (m, -CH 2 ethyl), TOF MS ES + 417 M + , other fragments are 400 m + , 326 m + , 293 m + , 258 m + ; CHN Analysis calcted (%) for C 22 H 22 N 7 O 2 : C, 63.30; H, 5.55; N, 23.49; found: C, 63.10; H, 5.25; N, 23.29. Docking Methodology (i) Ligand and Protein preparation: A library of fifty quinolone substituted 1,3,4-oxadiazole derivatives (4a-l) were prepared in Chem draw professional 15 by exploring the quinolone-based literatures from various sources. These ligands (4a-l) were included to the ligand library in an attempt to determine the most prominent lead derivative responsible for the development of significant antibacterial quinolone with the ease of developing the most probable substitution involved in the inhibition of bacterial DNA synthesis [26]. Furthermore, the macromolecular target involved in bacterial DNA transcription and replication processes was also explored from various quinolone literature. It has been observed that the DNA gyrase as essential bacterial enzyme which actively involved in bacterial DNA synthesis. Therefore, the complex co-crystallized structure of DNA gyrase ( topoisomerase II ) as target sites ( gram +ve & gram -ve ) with COX-II were retrieved from protein databank i.e. gram +ve (PDB id: 2w9s & 1yzf), gram –ve (PDB id: 6cqa & 6m1j) and 5ikr. All the target structures were downloaded in .Pdb format and pre-processed by adding hydrogens with gasteiger charges. Further water molecules were deleted and saved it in PDBQT format [27]. ii) Molecular Docking Studies After the successfully preparation of ligand and protein structures with proper selection of grid parameters rigid docking of ligands at defined pockets of DNA gyrase and COX-II target site was performed in Autodock format. Thereafter, best nine poses were obtained as output which confirmed the best binding interaction of docked ligands at target sites. We were able to choose the optimal ligand pose at the target site by carefully examining the binding interactions and dock scores among these poses [28]. Antibacterial & Antifungal activity The antimicrobial efficacy of the quinolone derivatives (4a-l) were assessed using the MTT assay [29], following established protocols for antimycobacterial activity evaluation. In a 96-well flat-bottom plate, each quinolone derivative was subjected to two-fold serial dilution using sterile distilled water. Subsequently, test strains of Staphylococcus aureus (ATCC 25923), Enterococcus faecalis (ATCC 29212), Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (27853) and candida albicans (ATCC 10231) were adjusted to a McFarland standard of 0.5, and 100 µL of the bacterial and fungal suspensions were added to each well separately in three replicates using a micropipette. The concentrations of the quinolone derivatives tested ranged from 2.5 to 640 µg/mL. As controls, wells containing bacterial growth without treatment, bacterial growth treated with Pipemidic acid, and bacterial growth treated with the antibiotic Ciprofloxacin were utilized as negative and positive controls, respectively. For the antifungal activity, synthesized quinolone substituted 1,3,4-oxadiazole derivatives (4a-l) were assessed using the MTT assay against Candida albicans (ATCC 10231) and fluconazole was used as reference positive control. The plates were covered, placed in zip-lock plastic bags, and incubated at 37°C for 24 hours. Following the incubation period, 20 µL of a 5 mg/mL MTT dye solution was added and left to incubate in the dark at 37°C for 4 hours. Afterwards, the supernatant was discarded, and the formazan precipitate was dissolved in dimethyl sulfoxide (DMSO). The plates were re-incubated for an additional 30 minutes, and absorbance was measured at 570 nm using a Spectramax spectrophotometer. The color change in the wells containing DMSO was indicative of the presence of viable cells, with violet color signifying bacterial growth and yellow color indicating the absence of viable cells. Biological screening Animals The Institutional Animal Ethical Committee approved the protocol for conducting the experiment (Registration No MMCP-IAEC-90). Wistar rats of either sex weighing 200-250 gm were used for the anti-inflammatory investigation. They had unrestricted access to water, a typical diet, and a standard facility. Acute toxicological study Acute toxicity was investigated, and the safe dose was determined using OECD test guideline 425 [30]. Anti-inflammatory activity Animals were grouped. Each group has six animals. The anti-inflammatory effect of the test compounds was tested using carrageenan-induced paw oedema in rats [31]. Different groups of rats received 50 mg/kg oral pre-treatment. Each rat received 0.1 ml of 1% carrageenan suspension into the sub-plantar region of its left hind paw after 1 hour to produce oedema. A plethysmometer (Laboratory enterprises, Nasik) was used to assess paw volume at 0, 1, 2, 3, and 4 hours. Naproxen (50 mg/kg p.o.) was standard. Mean ± SEM is determined and compared for treated and control animals at each time interval for statistical analysis. Conclusion Novel synthesized quinolone derivatives (4a-l) were designed, synthesized, and characterized using different spectroscopic techniques. All the synthesized hybrid molecules were evaluated for their antimicrobial and in vivo anti-inflammatory activities. Compounds 4f, 4h & 4k showed potent hybrid with maximum antibacterial activity against Staphylococcus aureus , Escherichia coli and Pseudomonas aeruginosa with MICs range of 8 µg/mL. Compound 4K exhibited potent anti-inflammatory activity which has a 3-amethylphenyl oxadiazole substitution on the C-6 position of pipemidic acid core structure and lacked antifungal efficacy against the candida albicans (ATCC 10231) fungal strain. Based on docking studies, the pipemidic acid substituted phenyl with oxadiazole functionality at position C-6 was actively implicated in a variety of binding interactions with the DNA gyrase active sites of bacterial strains including Pseudomonas aeruginosa , Escherichia coli , and Staphylococcus aureus . Understanding the interaction between various amino acids of the target protein sheds light on their ability to inhibit DNA gyrase. The study found that the presence of electron withdrawing and donating substitutions at the C-6 position resulted in improved antibacterial and anti-inflammatory activity. 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CA Winter, EA Risley, GW Nuss, Carrageenin-induced edema in hind paw of the rat as an assay for antiinflammatory drugs, Proc Soc Exp Biol Med 111:544–547. https://doi.org/10.3181/00379727-111-27849. Scheme Scheme 1 is available in the Supplementary Files section. Additional Declarations No competing interests reported. Supplementary Files schem1.png Scheme:1 Synthesis of novel quinolone substituted 1,3,4-oxadiazole derivatives 4(a-l), i (H 2 SO 4 , C 2 H 2 OH), refluxing 8 hours ii (NH 2 .NH 2 ), iii (RCOOH, POCl 3 ), refluxing 2 hours. GraphicalAbstract.png Cite Share Download PDF Status: Published Journal Publication published 03 Aug, 2024 Read the published version in Molecular Diversity → Version 1 posted Editorial decision: Revision requested 19 May, 2024 Editor assigned by journal 29 Apr, 2024 Submission checks completed at journal 28 Apr, 2024 First submitted to journal 27 Apr, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4334362","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":297639181,"identity":"4504c588-12eb-4612-9e3c-f76dead29920","order_by":0,"name":"Vishal Sharma","email":"","orcid":"","institution":"MM College of Pharmacy, Maharishi Markandeshwar (Deemed to be University)","correspondingAuthor":false,"prefix":"","firstName":"Vishal","middleName":"","lastName":"Sharma","suffix":""},{"id":297639182,"identity":"6976211b-4c89-48cc-b0b0-e4b2f633e9d1","order_by":1,"name":"Rina Das","email":"","orcid":"","institution":"MM College of Pharmacy, Maharishi Markandeshwar (Deemed to be University)","correspondingAuthor":false,"prefix":"","firstName":"Rina","middleName":"","lastName":"Das","suffix":""},{"id":297639183,"identity":"d04ba7d0-b7cf-417c-a950-1a06449f1179","order_by":2,"name":"Dinesh Kumar Mehta","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABAUlEQVRIie3PMWvCQBTA8XccxOVV1xxX/AaFk4BTqB+ky0khToKdFXudnNwV/BIi2DUQiEMvuGY0uFoQXAo6eHEsJKlbh/sPd8v9ePcAbLb/mAag5sLORplTNBsA5COsJhIeQYc58ZgCov5EfEilIZATgFJS11/d/dvPM5L5d7Y7DIT7NInMlJH/UkRYMl15M/mKlPe81kIIt627hsRBXxUQsX1Yc5QUHR44HMVl3A4NISoqI59nlO+ILK6dMZ+yzSpIMl1TlBG6ruPQG0krpjCdrDgGGxQYUHbbJTVTZMkudd1fntAfdkQtJsfDJf9YL9sdR34hKUje99xms9lsv7oCkcFcu2fb3zMAAAAASUVORK5CYII=","orcid":"","institution":"MM College of Pharmacy, Maharishi Markandeshwar (Deemed to be University)","correspondingAuthor":true,"prefix":"","firstName":"Dinesh","middleName":"Kumar","lastName":"Mehta","suffix":""},{"id":297639184,"identity":"a10817d4-545d-4397-9874-0d68522282be","order_by":3,"name":"Diksha Sharma","email":"","orcid":"","institution":"Swami Devidyal College of Pharmacy","correspondingAuthor":false,"prefix":"","firstName":"Diksha","middleName":"","lastName":"Sharma","suffix":""}],"badges":[],"createdAt":"2024-04-27 13:53:27","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4334362/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4334362/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s11030-024-10949-y","type":"published","date":"2024-08-03T15:57:34+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":55792932,"identity":"e9f2d82e-9161-475a-b7c5-05af254a7f11","added_by":"auto","created_at":"2024-05-03 09:53:16","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":96399,"visible":true,"origin":"","legend":"\u003cp\u003eSynthesized quinolone substituted 1,3,4- oxadiazole derivatives 4(a-l)\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-4334362/v1/674030028b447bdc1c859366.png"},{"id":55792934,"identity":"0ece2a98-c4d8-49ea-b939-3d97db3b27a4","added_by":"auto","created_at":"2024-05-03 09:53:17","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":301273,"visible":true,"origin":"","legend":"\u003cp\u003e2D \u0026amp; 3D binding interaction of compound 4f with DNA gyrase active site of 2w9s (\u003cem\u003eS. aureus\u003c/em\u003e)\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-4334362/v1/153ab11d29492d21cbe88faa.png"},{"id":55792933,"identity":"b63c8edd-1b0c-456e-a69d-a2694345417b","added_by":"auto","created_at":"2024-05-03 09:53:16","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":282985,"visible":true,"origin":"","legend":"\u003cp\u003e2D \u0026amp; 3D binding interactions of compound 4f with DNA gyrase active site of 6cqa (\u003cem\u003eE. coli\u003c/em\u003e)\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-4334362/v1/32451de065034d320e976de0.png"},{"id":55792935,"identity":"381a6bed-cf3a-42ae-8d8f-45fbfa7abd05","added_by":"auto","created_at":"2024-05-03 09:53:17","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":340819,"visible":true,"origin":"","legend":"\u003cp\u003e2D \u0026amp; 3D binding interactions of compound 4f with DNA gyrase active site of 6m1j (\u003cem\u003eP. aeruginosa\u003c/em\u003e)\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-4334362/v1/4497f1488ff6f97038b9cdd9.png"},{"id":55792929,"identity":"1077e2a4-166b-4671-9d33-4879112ec1de","added_by":"auto","created_at":"2024-05-03 09:53:16","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":321801,"visible":true,"origin":"","legend":"\u003cp\u003e2D \u0026amp; 3D binding interactions of compound 4h with DNA gyrase active site of 2w9s (\u003cem\u003eS. aureus\u003c/em\u003e)\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-4334362/v1/5cb6d99dd81a740b1534e6a3.png"},{"id":55792937,"identity":"3ce90a71-74d3-4db0-a3a9-37dd9b127730","added_by":"auto","created_at":"2024-05-03 09:53:17","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":377483,"visible":true,"origin":"","legend":"\u003cp\u003e2D \u0026amp; 3D binding interactions of compound 4h with DNA gyrase active site of 6cqa (\u003cem\u003eE. coli\u003c/em\u003e)\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-4334362/v1/1477153e70ef1430056b5153.png"},{"id":55793382,"identity":"fc5a9947-bfaa-4b3e-a1f0-fbc9a6afcdd7","added_by":"auto","created_at":"2024-05-03 10:01:17","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":304056,"visible":true,"origin":"","legend":"\u003cp\u003e2D \u0026amp; 3D binding interactions of compound 4h with DNA gyrase active site of 6m1j (\u003cem\u003eP. aeruginosa\u003c/em\u003e)\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-4334362/v1/0510254684a5c302460b2a17.png"},{"id":55792939,"identity":"03c920fa-8b39-4fea-b389-7f356c75db83","added_by":"auto","created_at":"2024-05-03 09:53:17","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":316986,"visible":true,"origin":"","legend":"\u003cp\u003e2D \u0026amp; 3D binding interactions of compound 4k with DNA gyrase active site of 2w9s (\u003cem\u003eS. aureus\u003c/em\u003e)\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-4334362/v1/a53f934237abf5295c522f1e.png"},{"id":55792942,"identity":"bb5ed8a8-e61f-4303-a77d-a20c6ab584ca","added_by":"auto","created_at":"2024-05-03 09:53:18","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":295638,"visible":true,"origin":"","legend":"\u003cp\u003e2D \u0026amp; 3D binding interactions of compound 4K with DNA gyrase active site of 6cqa (\u003cem\u003eE. coli\u003c/em\u003e)\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-4334362/v1/f8f97094c0db14387d57bc99.png"},{"id":55792936,"identity":"3a5987f0-d111-4998-840c-7338a9a79636","added_by":"auto","created_at":"2024-05-03 09:53:17","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":305425,"visible":true,"origin":"","legend":"\u003cp\u003e2D \u0026amp; 3D binding interactions of compound 4K with DNA gyrase active site of 6m1j (\u003cem\u003eP. aeruginosa\u003c/em\u003e)\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-4334362/v1/75b2d68f58e4441e96f21be1.png"},{"id":55792941,"identity":"f1beed88-0a19-48ff-927a-684f23da5843","added_by":"auto","created_at":"2024-05-03 09:53:17","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":343757,"visible":true,"origin":"","legend":"\u003cp\u003e2D \u0026amp; 3D binding interactions of compound 4K with target site of 5ikr (\u003cem\u003eCOX- II\u003c/em\u003e)\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-4334362/v1/d04b97d88ee5bbd41fa62f99.png"},{"id":61794487,"identity":"f6d34dfd-ab95-49a1-b95b-96c6dfed00d0","added_by":"auto","created_at":"2024-08-05 16:18:23","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4035244,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4334362/v1/ca846ba1-ccdc-4202-860b-b4b772b2e488.pdf"},{"id":55792940,"identity":"904b2a3c-a61a-46df-aaab-d26eb69def96","added_by":"auto","created_at":"2024-05-03 09:53:17","extension":"png","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":22570,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eScheme:1 \u003c/strong\u003eSynthesis of novel quinolone substituted 1,3,4-oxadiazole derivatives 4(a-l), i (H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e, C\u003csub\u003e2\u003c/sub\u003eH\u003csub\u003e2\u003c/sub\u003eOH), refluxing 8 hours ii (NH\u003csub\u003e2\u003c/sub\u003e.NH\u003csub\u003e2\u003c/sub\u003e), iii (RCOOH, POCl\u003csub\u003e3\u003c/sub\u003e), refluxing 2 hours.\u003c/p\u003e","description":"","filename":"schem1.png","url":"https://assets-eu.researchsquare.com/files/rs-4334362/v1/989cc89a920d003f626a255e.png"},{"id":55792931,"identity":"726b8463-3a5e-4061-97a2-b31abfde9bd3","added_by":"auto","created_at":"2024-05-03 09:53:16","extension":"png","order_by":5,"title":"","display":"","copyAsset":false,"role":"supplement","size":204908,"visible":true,"origin":"","legend":"","description":"","filename":"GraphicalAbstract.png","url":"https://assets-eu.researchsquare.com/files/rs-4334362/v1/8a6aa77655629beaf2fe2c3d.png"}],"financialInterests":"No competing interests reported.","formattedTitle":"Novel Quinolone substituted 1,3,4-oxadiazole derivatives: Design, synthesis, antimicrobial and anti-inflammatory potential","fulltext":[{"header":"Highlights","content":"\u003cul\u003e\n \u003cli\u003eQuinolone hybrid oxadiazole derivatives were docked into active site of gram +ve, gram \u0026ndash;ve and \u003cem\u003eCOX-II\u003c/em\u003e target sites.\u003c/li\u003e\n \u003cli\u003eMost prominent 12 derivatives were synthesized based on the best binding score.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eCompounds 4f, 4h \u0026amp; 4k\u003c/strong\u003e showed potent antibacterial activity against \u003cem\u003eStaphylococcus aureus\u003c/em\u003e, \u003cem\u003eEscherichia coli\u0026nbsp;\u003c/em\u003eand \u003cem\u003ePseudomonas aeruginosa\u0026nbsp;\u003c/em\u003ebacterial strains.\u003c/li\u003e\n \u003cli\u003eCompound \u003cstrong\u003e4K\u003c/strong\u003e showed maximum anti-inflammatory activity.\u003c/li\u003e\n\u003c/ul\u003e"},{"header":"Introduction","content":"\u003cp\u003eDespite the fact that microorganisms are vital to the ecosystem's operation, they pose a grave threat to human life and health. Antibiotic resistance is a growing hazard to humanity. At least 50,000 people die daily from drug-related illnesses in developed and developing nations, according to WHO figures. The current situation of available medications can be attributed to the extensive utilization of existing drugs, including their limited antibacterial spectrum, hypersensitivity, and antimicrobial resistance (AMR) as undesirable side effects [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. The persistent severity of antibiotic resistance has led to extensive research in the development of more bioactive molecules. To address the challenges associated with microbial resistance, there is an urgent need for thorough scientific investigation and research to develop safe and efficient antimicrobial drugs. Undoubtedly, significant attention has been drawn to nitrogen-containing heterocyclic aromatic molecules over the past two centuries, such as the quinolone moiety, to create novel synthetic agents with potent antimicrobial properties [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Quinolones are the most widely used antibacterial agents due to their bioavailability and extensive use. Its antibacterial activity comes from interfering with topoisomerase II (DNA gyrase and IV), which are critical for bacterial DNA synthesis and replication. [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Based on a literature review, quinolones demonstrated several biological profiles in addition to their ability to fight bacteria like anti-inflammatory [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], anti-HCV [6], anti-cancer [\u003cspan additionalcitationids=\"CR8 CR9 CR10\" citationid=\"CR6\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e11\u003c/span\u003e], anti-malarial [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e13\u003c/span\u003e], anti-HIV [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e15\u003c/span\u003e], and antidepressant activities [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Many quinolone derivatives are used in clinics as antibacterial drugs, such as MCB3837, MCB3681, CBR-2092 (rifamycin-quinolone conjugate), and Ro-23-9424 (in phase II clinical study) to treat a variety of infections [\u003cspan additionalcitationids=\"CR18\" citationid=\"CR16\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. The antibacterial potential of pipemidic acid and quinolone is just one of many therapeutic benefits [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. The incorporation of the 1,3,4-oxadiazole motif into the core structure of pipemidic acid has attracted significant interest and is widely regarded as a prominent approach to address resistance-related problems [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. The structural alteration of the quinolone core skeleton at the C-6 position has been regarded to be an efficient strategy to circumvent antibiotic resistance issues and preserve inhibitory efficacy in response to multidrug-resistant microbes.\u003c/p\u003e \u003cp\u003eComputer modelling tools simplify understanding the binding and important active site residues of unidentified target molecules. Structure and ligand-based drug design predict better ligands to strengthen interaction and increase target site potency [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. In the present investigation, we used comprehensive molecular modeling to investigate the binding manner, and essential active interactions and estimate their binding affinity of the ligands using different PDB ids of DNA \u003cem\u003etopoisomerases\u003c/em\u003e as the target. Furthermore, structural alteration of the quinolone skeleton at the C-6 position may avoid antibiotic resistance processes while maintaining inhibitory activity against multidrug-resistant bacteria [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. We have great interest in integrating the oxadiazole motif to pipemidic acid quinolone at the C-6 position to develop new antibacterial molecules. Pipemidic acid, with the introduction of oxadiazole moiety at C-6 position exhibited potent bacterial action against resistance microbes [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. From perusal of the literature, we targeted the design, synthesis and biological evaluation of novel quinolone containing oxadiazole derivatives for their antimicrobial and anti-inflammatory potential.\u003c/p\u003e"},{"header":"Results and discussion","content":"\u003cp\u003eOur study commenced by synthesizing the title quinolone derivatives \u003cstrong\u003e(4a-l)\u003c/strong\u003e in three steps is outlined in Scheme-1. In the step-I, the synthesis of ethyl 8-ethyl-5-oxo-2-(piperazin-1-yl)-5, 8-dihydropyrido[2,3-\u003cem\u003ed\u003c/em\u003e]pyrimidine-6-carboxylate \u003cstrong\u003e(2)\u003c/strong\u003e\u0026nbsp; was done by esterification of pipemidic acid \u003cstrong\u003e(1)\u003c/strong\u003e. In step-II ester \u003cstrong\u003e(2)\u003c/strong\u003e was further treated with hydrazine hydrate to afford the corresponding 8-ethyl-5-oxo-2-(piperazin-1-yl)-5,8-dihydropyrido[2,3-\u003cem\u003ed\u003c/em\u003e]pyrimidine-6-carbohydrazide \u003cstrong\u003e(3)\u003c/strong\u003e in 70-80% yield. Step-III involves synthesis of title pipemidic acid containing oxadiazole derivatives \u003cstrong\u003e(4)\u003c/strong\u003e by refluxing equimolar mixture (1:1) of hydrazide \u003cstrong\u003e(3)\u003c/strong\u003e with different aromatic carboxylic acid \u003cstrong\u003e(I-XII)\u003c/strong\u003e in the presence of phosphorous oxychloride for 2\u0026ndash;3 h (Scheme-1). The completion of the reaction was monitored by TLC using chloroform: ethanol (10:1) solvent system. The synthesized derivatives (figure 1) were purified by column chromatographic technique. The structures of synthesized pipemidic acid hybrid derivatives 4(a-l) were confirmed by IR, NMR, Mass spectroscopy and elemental analysis. The functional group identification was done using FTIR based on characteristic absorption bands corresponding to \u0026ndash;NH, -C=O, -CH aromatic \u0026amp; -CH aliphatic and \u0026ndash;C=N groups. FTIR spectra of all synthesized pipemidic acid derivatives reported \u0026ndash;NH stretching in the range of 3340-3500 cm\u003csup\u003e-1\u003c/sup\u003e. The vibrational frequency at 1617-1720 cm\u003csup\u003e-1\u003c/sup\u003e showed the presence of carbonyl moiety in synthesized derivatives. Other characteristic peaks for \u0026ndash;CH aliphatic, -CH aromatic and \u0026ndash;C=N were reported at 2914-2927 cm\u003csup\u003e-1\u003c/sup\u003e, 3100-3250 cm\u003csup\u003e-1\u003c/sup\u003e and 1383-1477 cm\u003csup\u003e-1\u003c/sup\u003e respectively. Furthermore, NMR spectra of synthesized analogues showed peak at \u0026delta; 1.1-1.4 ppm and doublet signal for aromatic hydrogens at \u0026delta; 7.0-8.0 ppm. The signal for \u0026ndash;CH\u003csub\u003e2\u003c/sub\u003e of piperazine ring showed in between \u0026delta; 2.0-3.0 ppm and singlet peak for C-4 and C-7 hydrogen of pyridopyrimidine ring in pipemidic acid derivatives at \u0026delta; 7.4-7.7 ppm. MS spectra depicted specific molecular ion (M\u003csup\u003e+\u003c/sup\u003e) peak correlated to the molecular weight of synthesized compounds. \u0026nbsp; \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMolecular Docking Studies\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIn this study, the three-dimensional crystal structure of quinolones with DNA gyrase (topoisomerase II) from gram-positive and gram-negative bacteria and COX-II was employed. For docking study, library of fifty molecules was docked into the binding site of receptor using Autodock 4.2. \u0026nbsp;In this investigation, the docking score and H-bond interactions of synthesized derivatives were computed and shown as dotted green color lines. Out of all screened compounds, twelve derivatives were estimated to be having best binding affinity in terms of kcal/mol with common residues (ARG72, ARG78, ARG57, LYS32, SER49, LEU54, ILE94, ALA6, THR100, PHE31, MET16) and exhibited confirmed free energy of binding ranged from -4.5 to -8.6 kcal/mol, as shown in figures (2-11). Compound \u003cstrong\u003e4f, 4h \u0026amp; 4k\u003c/strong\u003e estimated best free energy of binding, -8.4, -8.6 \u0026amp; -8.5 kcal/mol into the binding pocket of DNA gyrase enzyme respectively even better in comparison to reference ligands, as represented in figure 2, 5 \u0026amp; 8 and exhibited highest hydrogen bonding interaction with amino acids ARG57, ARG72 \u0026amp; ARG78. Furthermore, compound \u003cstrong\u003e4K\u003c/strong\u003e confirmed to be having significant docking score -8.20 kcal/mol in protein target (5ikr) of \u003cem\u003eCOX-II\u003c/em\u003e and hydrogen bonding interaction with amino acids TYR355 \u0026amp; ARG120. The docked structures of 4f, 4h \u0026amp; 4k with these target sites confirmed that the electron withdrawing \u0026amp; donating functionality at C-6 position of pipemidic acid showed significant interactions with different amino acid residues at target site. The binding score of each of the ligand library against the DNA gyrase is tabulated in Table. 1.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1:\u0026nbsp;\u003c/strong\u003eDocking results of synthesized quinolone substituted 1,3,4-oxadiazole derivatives\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cdiv align=\"\"\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"578\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"9.32642487046632%\" rowspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eS. No.\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.962003454231432%\" rowspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eCompound\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"72.71157167530224%\" colspan=\"5\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eDocking Score (kcal/mol))\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"22.511848341232227%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eStreptococcus aureus(+ve)\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e2w9s\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.14218009478673%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eEnterococcus faecalis(+ve)\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e1yzf\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.061611374407583%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eE. coli\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003e(-ve)\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e6cqa\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"24.644549763033176%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003ePseudomonas aeruginosa (-ve)\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e6m1j\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.639810426540285%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eCOX-II\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(5ikr)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"9.310344827586206%\" valign=\"top\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.93103448275862%\" valign=\"top\"\u003e\n \u003cp\u003e4a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.379310344827587%\" valign=\"top\"\u003e\n \u003cp\u003e-7.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.655172413793103%\" valign=\"top\"\u003e\n \u003cp\u003e-7.09\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.413793103448276%\" valign=\"top\"\u003e\n \u003cp\u003e-8.30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.93103448275862%\" valign=\"top\"\u003e\n \u003cp\u003e-7.63\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.379310344827585%\" valign=\"top\"\u003e\n \u003cp\u003e-6.44\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"9.310344827586206%\" valign=\"top\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.93103448275862%\" valign=\"top\"\u003e\n \u003cp\u003e4b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.379310344827587%\" valign=\"top\"\u003e\n \u003cp\u003e-4.48\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.655172413793103%\" valign=\"top\"\u003e\n \u003cp\u003e-6.48\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.413793103448276%\" valign=\"top\"\u003e\n \u003cp\u003e-7.90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.93103448275862%\" valign=\"top\"\u003e\n \u003cp\u003e-7.13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.379310344827585%\" valign=\"top\"\u003e\n \u003cp\u003e-7.56\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"9.310344827586206%\" valign=\"top\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.93103448275862%\" valign=\"top\"\u003e\n \u003cp\u003e4c\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.379310344827587%\" valign=\"top\"\u003e\n \u003cp\u003e-5.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.655172413793103%\" valign=\"top\"\u003e\n \u003cp\u003e-6.14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.413793103448276%\" valign=\"top\"\u003e\n \u003cp\u003e-7.76\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.93103448275862%\" valign=\"top\"\u003e\n \u003cp\u003e-8.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.379310344827585%\" valign=\"top\"\u003e\n \u003cp\u003e-6.86\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"9.310344827586206%\" valign=\"top\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.93103448275862%\" valign=\"top\"\u003e\n \u003cp\u003e4d\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.379310344827587%\" valign=\"top\"\u003e\n \u003cp\u003e-4.15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.655172413793103%\" valign=\"top\"\u003e\n \u003cp\u003e-5.80\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.413793103448276%\" valign=\"top\"\u003e\n \u003cp\u003e-7.41\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.93103448275862%\" valign=\"top\"\u003e\n \u003cp\u003e-7.71\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.379310344827585%\" valign=\"top\"\u003e\n \u003cp\u003e-6.34\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"9.310344827586206%\" valign=\"top\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.93103448275862%\" valign=\"top\"\u003e\n \u003cp\u003e4e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.379310344827587%\" valign=\"top\"\u003e\n \u003cp\u003e-4.36\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.655172413793103%\" valign=\"top\"\u003e\n \u003cp\u003e-6.36\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.413793103448276%\" valign=\"top\"\u003e\n \u003cp\u003e-7.21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.93103448275862%\" valign=\"top\"\u003e\n \u003cp\u003e-7.79\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.379310344827585%\" valign=\"top\"\u003e\n \u003cp\u003e-6.87\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"9.310344827586206%\" valign=\"top\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.93103448275862%\" valign=\"top\"\u003e\n \u003cp\u003e4f\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.379310344827587%\" valign=\"top\"\u003e\n \u003cp\u003e-8.40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.655172413793103%\" valign=\"top\"\u003e\n \u003cp\u003e-6.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.413793103448276%\" valign=\"top\"\u003e\n \u003cp\u003e-8.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.93103448275862%\" valign=\"top\"\u003e\n \u003cp\u003e-8.22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.379310344827585%\" valign=\"top\"\u003e\n \u003cp\u003e-8.05\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"9.310344827586206%\" valign=\"top\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.93103448275862%\" valign=\"top\"\u003e\n \u003cp\u003e4g\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.379310344827587%\" valign=\"top\"\u003e\n \u003cp\u003e-6.15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.655172413793103%\" valign=\"top\"\u003e\n \u003cp\u003e-6.23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.413793103448276%\" valign=\"top\"\u003e\n \u003cp\u003e-7.76\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.93103448275862%\" valign=\"top\"\u003e\n \u003cp\u003e-8.09\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.379310344827585%\" valign=\"top\"\u003e\n \u003cp\u003e-5.97\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"9.310344827586206%\" valign=\"top\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.93103448275862%\" valign=\"top\"\u003e\n \u003cp\u003e4h\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.379310344827587%\" valign=\"top\"\u003e\n \u003cp\u003e-8.63\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.655172413793103%\" valign=\"top\"\u003e\n \u003cp\u003e-6.27\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.413793103448276%\" valign=\"top\"\u003e\n \u003cp\u003e-8.16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.93103448275862%\" valign=\"top\"\u003e\n \u003cp\u003e-8.09\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.379310344827585%\" valign=\"top\"\u003e\n \u003cp\u003e-8.00\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"9.310344827586206%\" valign=\"top\"\u003e\n \u003cp\u003e9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.93103448275862%\" valign=\"top\"\u003e\n \u003cp\u003e4i\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.379310344827587%\" valign=\"top\"\u003e\n \u003cp\u003e-4.21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.655172413793103%\" valign=\"top\"\u003e\n \u003cp\u003e-6.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.413793103448276%\" valign=\"top\"\u003e\n \u003cp\u003e-7.66\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.93103448275862%\" valign=\"top\"\u003e\n \u003cp\u003e-6.83\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.379310344827585%\" valign=\"top\"\u003e\n \u003cp\u003e-4.67\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"9.310344827586206%\" valign=\"top\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.93103448275862%\" valign=\"top\"\u003e\n \u003cp\u003e4j\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.379310344827587%\" valign=\"top\"\u003e\n \u003cp\u003e-4.23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.655172413793103%\" valign=\"top\"\u003e\n \u003cp\u003e-6.82\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.413793103448276%\" valign=\"top\"\u003e\n \u003cp\u003e-7.86\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.93103448275862%\" valign=\"top\"\u003e\n \u003cp\u003e-6.23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.379310344827585%\" valign=\"top\"\u003e\n \u003cp\u003e-6.44\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"9.310344827586206%\" valign=\"top\"\u003e\n \u003cp\u003e11.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.93103448275862%\" valign=\"top\"\u003e\n \u003cp\u003e4k\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.379310344827587%\" valign=\"top\"\u003e\n \u003cp\u003e-8.56\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.655172413793103%\" valign=\"top\"\u003e\n \u003cp\u003e-6.23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.413793103448276%\" valign=\"top\"\u003e\n \u003cp\u003e-8.07\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.93103448275862%\" valign=\"top\"\u003e\n \u003cp\u003e-8.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.379310344827585%\" valign=\"top\"\u003e\n \u003cp\u003e-8.20\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"9.310344827586206%\" valign=\"top\"\u003e\n \u003cp\u003e12.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.93103448275862%\" valign=\"top\"\u003e\n \u003cp\u003e4l\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.379310344827587%\" valign=\"top\"\u003e\n \u003cp\u003e-5.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.655172413793103%\" valign=\"top\"\u003e\n \u003cp\u003e-6.46\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.413793103448276%\" valign=\"top\"\u003e\n \u003cp\u003e-7.95\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.93103448275862%\" valign=\"top\"\u003e\n \u003cp\u003e-8.14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.379310344827585%\" valign=\"top\"\u003e\n \u003cp\u003e-7.76\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"9.310344827586206%\" valign=\"top\"\u003e\n \u003cp\u003e13.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.93103448275862%\" valign=\"top\"\u003e\n \u003cp\u003eCiprofloxacin/Naproxen\u003cstrong\u003e*\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.379310344827587%\" valign=\"top\"\u003e\n \u003cp\u003e-7.21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.655172413793103%\" valign=\"top\"\u003e\n \u003cp\u003e-5.62\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.413793103448276%\" valign=\"top\"\u003e\n \u003cp\u003e-7.64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.93103448275862%\" valign=\"top\"\u003e\n \u003cp\u003e-7.86\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.379310344827585%\" valign=\"top\"\u003e\n \u003cp\u003e-7.75*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"9.310344827586206%\" valign=\"top\"\u003e\n \u003cp\u003e14.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.93103448275862%\" valign=\"top\"\u003e\n \u003cp\u003ePipemidic Acid\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.379310344827587%\" valign=\"top\"\u003e\n \u003cp\u003e-6.71\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.655172413793103%\" valign=\"top\"\u003e\n \u003cp\u003e-6.40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.413793103448276%\" valign=\"top\"\u003e\n \u003cp\u003e-7.45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.93103448275862%\" valign=\"top\"\u003e\n \u003cp\u003e-7.87\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.379310344827585%\" valign=\"top\"\u003e\n \u003cp\u003e-6.67\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003ch3\u003eBIOLOGICAL ACTIVITY\u003c/h3\u003e\n\u003cp\u003e\u003cstrong\u003eScreening of antibacterial and antifungal activities\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll quinolone substituted 1,3,4-oxadiazole derivatives (4a-l) were tested for antibacterial and antifungal activity to determine their MIC values against gram-positive (\u003cem\u003eStaphylococcus aureus\u003c/em\u003e \u0026amp; \u003cem\u003eEnterococcus faecalis\u003c/em\u003e, gram-negative (\u003cem\u003eEscherichia coli\u003c/em\u003e \u0026amp; \u003cem\u003ePseudomonas aeruginosa\u003c/em\u003e and fungal strains. Pipemidic acid was employed as a positive control and ciprofloxacin (CIP) and fluconazole as standards (Table 2). SARAccording to the antibacterial data, newly synthesized compounds profoundly impact the antibacterial profile of Gram-positive and negative bacterial strains. The compounds exhibited a moderate activity against \u003cem\u003eE. faecalis\u003c/em\u003e and a considerable inhibitory effect against \u003cem\u003eS. aureus\u003c/em\u003e, \u003cem\u003eE. coli\u003c/em\u003e, and \u003cem\u003eP. aeruginosa\u003c/em\u003e.\u0026nbsp;Out of the tested derivatives, compounds 4i \u0026amp; 4j were found to be least active against gram positive and gram negative bacteria with MIC value of 64-512\u0026nbsp;\u0026micro;g/mL; however compounds 4a-4e, 4g \u0026amp; 4i exhibited moderate activity against gram positive \u0026amp; negative strain.\u0026nbsp;These biological data exhibited an unexpected structure-activity relationship (SAR), showing that pipemidic acid\u0026apos;s antibacterial potency was greatly impacted by the sixth carbon atom substitution.\u0026nbsp;Specifically, the presence of electron-donating and releasing functionality with phenyl oxadiazole moiety at C-6 position considered effective for antibacterial activity.\u0026nbsp;On the other hand, it has been confirmed\u0026nbsp;that the pipemidic acid derivatives (4a\u0026ndash;l) lacked antifungal efficacy against the candida albicans fungal strain.\u0026nbsp;\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAnti-inflammatory activity\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe anti-inflammatory effect of synthesised derivatives (4a-l) was tested in rats with carrageenan-induced paw oedema and naproxen as a reference medication. In Table 2, results are shown as mean \u0026plusmn; S.D. One-way ANOVA and Tukey\u0026apos;s test were used to compare control and treatment groups for statistical significance. The test derivatives significantly reduced the volume of the paw oedema when given one hour before the carrageenan injection at a dose of 50 mg/kg body weight. Maximum anti-inflammatory action is conferred by compound 4k, which has a 3-methylphenyl oxadiazole substitution on the C-6 position of pipemidic core structure. Moderate anti-inflammatory activity is conferred by compounds 4f \u0026amp; 4h, which have 2-fluorophenyl and 2-chlorophenyl oxadiazole substitution. Paw oedema volume and % oedema inhibition values were strongly inhibited by the presence of methyl functionality as an electron-releasing group in the \u003cem\u003emeta\u003c/em\u003e position of the phenyl ring linked with oxadiazole moiety. These values were also extremely near to those of the standard compound.\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable: 2\u0026nbsp;\u003c/strong\u003eMICs of\u0026nbsp;synthesized quinolone substituted 1,3,4-oxadiazole derivatives(4a-l)\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"659\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"18.181818181818183%\" valign=\"top\"\u003e\n \u003cp\u003eCompound\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.727272727272727%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cem\u003eStaphylococcus aureus\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003e(ATCC 25923)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.515151515151516%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cem\u003eEnterococcus faecalis\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003e(ATCC 29212)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.454545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cem\u003eEscherichia\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003e\u003cem\u003ecoli\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003e(ATCC 25922)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.666666666666668%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cem\u003ePseudomonas aeruginosa\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003e(ATCC 27853)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.454545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cem\u003eCandida albicans\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003e(ATCC 10231)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"18.181818181818183%\" valign=\"top\"\u003e\n \u003cp\u003e4a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.727272727272727%\" valign=\"top\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.515151515151516%\" valign=\"top\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.454545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.666666666666668%\" valign=\"top\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.454545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"18.181818181818183%\" valign=\"top\"\u003e\n \u003cp\u003e4b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.727272727272727%\" valign=\"top\"\u003e\n \u003cp\u003e512\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.515151515151516%\" valign=\"top\"\u003e\n \u003cp\u003e64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.454545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.666666666666668%\" valign=\"top\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.454545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"18.181818181818183%\" valign=\"top\"\u003e\n \u003cp\u003e4c\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.727272727272727%\" valign=\"top\"\u003e\n \u003cp\u003e128\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.515151515151516%\" valign=\"top\"\u003e\n \u003cp\u003e64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.454545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.666666666666668%\" valign=\"top\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.454545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"18.181818181818183%\" valign=\"top\"\u003e\n \u003cp\u003e4d\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.727272727272727%\" valign=\"top\"\u003e\n \u003cp\u003e512\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.515151515151516%\" valign=\"top\"\u003e\n \u003cp\u003e256\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.454545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.666666666666668%\" valign=\"top\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.454545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"18.181818181818183%\" valign=\"top\"\u003e\n \u003cp\u003e4e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.727272727272727%\" valign=\"top\"\u003e\n \u003cp\u003e256\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.515151515151516%\" valign=\"top\"\u003e\n \u003cp\u003e64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.454545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.666666666666668%\" valign=\"top\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.454545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026gt;1024\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"18.181818181818183%\" valign=\"top\"\u003e\n \u003cp\u003e4f\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.727272727272727%\" valign=\"top\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.515151515151516%\" valign=\"top\"\u003e\n \u003cp\u003e64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.454545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.666666666666668%\" valign=\"top\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.454545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"18.181818181818183%\" valign=\"top\"\u003e\n \u003cp\u003e4g\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.727272727272727%\" valign=\"top\"\u003e\n \u003cp\u003e128\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.515151515151516%\" valign=\"top\"\u003e\n \u003cp\u003e64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.454545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.666666666666668%\" valign=\"top\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.454545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"18.181818181818183%\" valign=\"top\"\u003e\n \u003cp\u003e4h\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.727272727272727%\" valign=\"top\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.515151515151516%\" valign=\"top\"\u003e\n \u003cp\u003e64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.454545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.666666666666668%\" valign=\"top\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.454545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"18.181818181818183%\" valign=\"top\"\u003e\n \u003cp\u003e4i\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.727272727272727%\" valign=\"top\"\u003e\n \u003cp\u003e512\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.515151515151516%\" valign=\"top\"\u003e\n \u003cp\u003e128\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.454545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.666666666666668%\" valign=\"top\"\u003e\n \u003cp\u003e128\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.454545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e\u0026gt;1024\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"18.181818181818183%\" valign=\"top\"\u003e\n \u003cp\u003e4j\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.727272727272727%\" valign=\"top\"\u003e\n \u003cp\u003e512\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.515151515151516%\" valign=\"top\"\u003e\n \u003cp\u003e128\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.454545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.666666666666668%\" valign=\"top\"\u003e\n \u003cp\u003e128\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.454545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"18.181818181818183%\" valign=\"top\"\u003e\n \u003cp\u003e4k\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.727272727272727%\" valign=\"top\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.515151515151516%\" valign=\"top\"\u003e\n \u003cp\u003e64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.454545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.666666666666668%\" valign=\"top\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.454545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"18.181818181818183%\" valign=\"top\"\u003e\n \u003cp\u003e4l\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.727272727272727%\" valign=\"top\"\u003e\n \u003cp\u003e256\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.515151515151516%\" valign=\"top\"\u003e\n \u003cp\u003e64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.454545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.666666666666668%\" valign=\"top\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.454545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"18.181818181818183%\" valign=\"top\"\u003e\n \u003cp\u003ePA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.727272727272727%\" valign=\"top\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.515151515151516%\" valign=\"top\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.454545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.666666666666668%\" valign=\"top\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.454545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"18.181818181818183%\" valign=\"top\"\u003e\n \u003cp\u003eCIP/Fluconazole*\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"17.727272727272727%\" valign=\"top\"\u003e\n \u003cp\u003e0.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.515151515151516%\" valign=\"top\"\u003e\n \u003cp\u003e0.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.454545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e0.125\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.666666666666668%\" valign=\"top\"\u003e\n \u003cp\u003e0.125\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.454545454545455%\" valign=\"top\"\u003e\n \u003cp\u003e2*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003ePA: Pipemidic acid; CIP: Ciprofloxacin.\u0026nbsp;All\u0026nbsp;the\u0026nbsp;experiments\u0026nbsp;were\u0026nbsp;performed in triplicates (n=3), MIC represented in \u0026micro;g/ml, \u0026ldquo;-\u0026rdquo; no activity observed\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAnti-inflammatory activity:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable: 3\u0026nbsp;\u003c/strong\u003eEffect of synthesized derivatives\u0026nbsp;(4a-l) on carrageenan-induced paw oedema in rats\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.720257234726688%\" rowspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eCompounds\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"83.27974276527331%\" colspan=\"5\" valign=\"top\"\u003e\n \u003cp\u003ePaw volume (ml) (mean\u0026plusmn;SEM)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"19.535783365570598%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e0 hr\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.11605415860735%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e1 hr\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.11605415860735%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e2 hr\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.11605415860735%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e3 hr\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.11605415860735%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e4 hr\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e4a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.264090177133657%\" valign=\"top\"\u003e\n \u003cp\u003e0.97\u0026plusmn;0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.11\u0026plusmn;0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.19\u0026plusmn;0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.27\u0026plusmn;0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.33\u0026plusmn;0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e4b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.264090177133657%\" valign=\"top\"\u003e\n \u003cp\u003e0.90\u0026plusmn;0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.05\u0026plusmn;0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.09\u0026plusmn;0.01\u003csup\u003eb*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.12\u0026plusmn;0.02\u003csup\u003eb*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.23\u0026plusmn;0.02\u003csup\u003eb*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e4c\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.264090177133657%\" valign=\"top\"\u003e\n \u003cp\u003e0.90\u0026plusmn;0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e0.99\u0026plusmn;0.00\u003csup\u003eb*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.02\u0026plusmn;0.02\u003csup\u003eb*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.15\u0026plusmn;0.01\u003csup\u003eb*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.20\u0026plusmn;0.02\u003csup\u003eb*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e4d\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.264090177133657%\" valign=\"top\"\u003e\n \u003cp\u003e0.97\u0026plusmn;0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.15\u0026plusmn;0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.10\u0026plusmn;0.02\u003csup\u003eb*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.15\u0026plusmn;0.00\u003csup\u003eb*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.29\u0026plusmn;0.03\u003csup\u003eb*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e4e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.264090177133657%\" valign=\"top\"\u003e\n \u003cp\u003e0.86\u0026plusmn;0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e0.97\u0026plusmn;0.01\u003csup\u003eb*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.08\u0026plusmn;0.02\u003csup\u003eb*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.15\u0026plusmn;0.02\u003csup\u003eb*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.23\u0026plusmn;0.03\u003csup\u003eb*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e4f\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.264090177133657%\" valign=\"top\"\u003e\n \u003cp\u003e0.92\u0026plusmn;0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.06\u0026plusmn;0.01\u003csup\u003eb*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e0.96\u0026plusmn;0.02\u003csup\u003eb**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e0.85\u0026plusmn;0.01\u003csup\u003eb***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e0.86\u0026plusmn;0.02\u003csup\u003eb***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e4g\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.264090177133657%\" valign=\"top\"\u003e\n \u003cp\u003e0.93\u0026plusmn;0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.07\u0026plusmn;0.01\u003csup\u003eb*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.25\u0026plusmn;0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.29\u0026plusmn;0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.20\u0026plusmn;0.02\u003csup\u003eb*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e4h\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.264090177133657%\" valign=\"top\"\u003e\n \u003cp\u003e0.88\u0026plusmn;0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.07\u0026plusmn;0.01\u003csup\u003eb*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e0.95\u0026plusmn;0.01\u003csup\u003eb**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e0.83\u0026plusmn;0.01\u003csup\u003eb***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e0.86\u0026plusmn;0.02\u003csup\u003eb***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e4i\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.264090177133657%\" valign=\"top\"\u003e\n \u003cp\u003e0.89\u0026plusmn;0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e0.98\u0026plusmn;0.00\u003csup\u003eb*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.23\u0026plusmn;0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.25\u0026plusmn;0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.24\u0026plusmn;0.01\u003csup\u003eb*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e4j\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.264090177133657%\" valign=\"top\"\u003e\n \u003cp\u003e0.98\u0026plusmn;0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.18\u0026plusmn;0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.21\u0026plusmn;0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.28\u0026plusmn;0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.31\u0026plusmn;0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e4k\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.264090177133657%\" valign=\"top\"\u003e\n \u003cp\u003e0.90\u0026plusmn;0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.06\u0026plusmn;0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e0.97\u0026plusmn;0.02\u003csup\u003eb***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e0.86\u0026plusmn;0.01\u003csup\u003eb***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e0.82\u0026plusmn;0.01\u003csup\u003eb***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e4l\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.264090177133657%\" valign=\"top\"\u003e\n \u003cp\u003e0.90\u0026plusmn;0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.07\u0026plusmn;0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.08\u0026plusmn;0.02\u003csup\u003eb**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e0.92\u0026plusmn;0.03\u003csup\u003eb***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.11\u0026plusmn;0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003eNormal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.264090177133657%\" valign=\"top\"\u003e\n \u003cp\u003e0.81\u0026plusmn;0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e0.81\u0026plusmn;0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e0.82\u0026plusmn;0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e0.82\u0026plusmn;0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e0.8\u0026plusmn;0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003ePositive control\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.264090177133657%\" valign=\"top\"\u003e\n \u003cp\u003e0.98\u0026plusmn;0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.16\u0026plusmn;0.02\u003csup\u003ea**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.26\u0026plusmn;0.02\u003csup\u003ea***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.31\u0026plusmn;0.02\u003csup\u003ea***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e1.4\u0026plusmn;0.05\u003csup\u003ea***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003eStd\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.264090177133657%\" valign=\"top\"\u003e\n \u003cp\u003e0.88\u0026plusmn;0.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e0.98\u0026plusmn;0.004\u003csup\u003eb**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e0.93\u0026plusmn;0.00\u003csup\u003eb**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e0.84\u0026plusmn;0.01\u003csup\u003eb***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.74718196457327%\" valign=\"top\"\u003e\n \u003cp\u003e0.8\u0026plusmn;0.02\u003csup\u003eb***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eAll the values represent means of two determinations;\u0026nbsp;p\u0026lt;0.05=*, p\u0026lt;0.01=**, p\u0026lt;0.001=***\u003cstrong\u003e\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePercentage inhibition:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable: 4\u0026nbsp;\u003c/strong\u003eEffect of synthesized derivatives (4a-l) on carrageenan induced paw oedema in rats\u003c/p\u003e\n\u003cdiv align=\"center\"\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"11.01511879049676%\" rowspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eS.No.\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"24.838012958963283%\" rowspan=\"2\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eCompounds\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"64.14686825053995%\" colspan=\"5\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e% inhibition\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"17.50841750841751%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e0 hr\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.51851851851852%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e1 hr\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.51851851851852%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e2 hr\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"21.21212121212121%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e3 hr\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"24.242424242424242%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e4 hr\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"11.01511879049676%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e1.\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"24.838012958963283%\" valign=\"top\"\u003e\n \u003cp\u003e4a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23110151187905%\" valign=\"top\"\u003e\n \u003cp\u003e-1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.879049676025918%\" valign=\"top\"\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.879049676025918%\" valign=\"top\"\u003e\n \u003cp\u003e32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.606911447084233%\" valign=\"top\"\u003e\n \u003cp\u003e34\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.550755939524837%\" valign=\"top\"\u003e\n \u003cp\u003e43\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"11.01511879049676%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e2.\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"24.838012958963283%\" valign=\"top\"\u003e\n \u003cp\u003e4b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23110151187905%\" valign=\"top\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.879049676025918%\" valign=\"top\"\u003e\n \u003cp\u003e26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.879049676025918%\" valign=\"top\"\u003e\n \u003cp\u003e40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.606911447084233%\" valign=\"top\"\u003e\n \u003cp\u003e46\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.550755939524837%\" valign=\"top\"\u003e\n \u003cp\u003e50\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"11.01511879049676%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e3.\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"24.838012958963283%\" valign=\"top\"\u003e\n \u003cp\u003e4c\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23110151187905%\" valign=\"top\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.879049676025918%\" valign=\"top\"\u003e\n \u003cp\u003e32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.879049676025918%\" valign=\"top\"\u003e\n \u003cp\u003e46\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.606911447084233%\" valign=\"top\"\u003e\n \u003cp\u003e43\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.550755939524837%\" valign=\"top\"\u003e\n \u003cp\u003e52\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"11.01511879049676%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e4.\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"24.838012958963283%\" valign=\"top\"\u003e\n \u003cp\u003e4d\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23110151187905%\" valign=\"top\"\u003e\n \u003cp\u003e-1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.879049676025918%\" valign=\"top\"\u003e\n \u003cp\u003e18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.879049676025918%\" valign=\"top\"\u003e\n \u003cp\u003e39\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.606911447084233%\" valign=\"top\"\u003e\n \u003cp\u003e43\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.550755939524837%\" valign=\"top\"\u003e\n \u003cp\u003e45\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"11.01511879049676%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e5.\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"24.838012958963283%\" valign=\"top\"\u003e\n \u003cp\u003e4e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23110151187905%\" valign=\"top\"\u003e\n \u003cp\u003e11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.879049676025918%\" valign=\"top\"\u003e\n \u003cp\u003e33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.879049676025918%\" valign=\"top\"\u003e\n \u003cp\u003e41\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.606911447084233%\" valign=\"top\"\u003e\n \u003cp\u003e43\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.550755939524837%\" valign=\"top\"\u003e\n \u003cp\u003e50\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"11.01511879049676%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e6.\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"24.838012958963283%\" valign=\"top\"\u003e\n \u003cp\u003e4f\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23110151187905%\" valign=\"top\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.879049676025918%\" valign=\"top\"\u003e\n \u003cp\u003e25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.879049676025918%\" valign=\"top\"\u003e\n \u003cp\u003e50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.606911447084233%\" valign=\"top\"\u003e\n \u003cp\u003e66\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.550755939524837%\" valign=\"top\"\u003e\n \u003cp\u003e77\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"11.01511879049676%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e7.\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"24.838012958963283%\" valign=\"top\"\u003e\n \u003cp\u003e4g\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23110151187905%\" valign=\"top\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.879049676025918%\" valign=\"top\"\u003e\n \u003cp\u003e25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.879049676025918%\" valign=\"top\"\u003e\n \u003cp\u003e27\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.606911447084233%\" valign=\"top\"\u003e\n \u003cp\u003e32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.550755939524837%\" valign=\"top\"\u003e\n \u003cp\u003e52\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"11.01511879049676%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e8.\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"24.838012958963283%\" valign=\"top\"\u003e\n \u003cp\u003e4h\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23110151187905%\" valign=\"top\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.879049676025918%\" valign=\"top\"\u003e\n \u003cp\u003e24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.879049676025918%\" valign=\"top\"\u003e\n \u003cp\u003e51\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.606911447084233%\" valign=\"top\"\u003e\n \u003cp\u003e68\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.550755939524837%\" valign=\"top\"\u003e\n \u003cp\u003e77\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"11.01511879049676%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e9.\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"24.838012958963283%\" valign=\"top\"\u003e\n \u003cp\u003e4i\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23110151187905%\" valign=\"top\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.879049676025918%\" valign=\"top\"\u003e\n \u003cp\u003e32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.879049676025918%\" valign=\"top\"\u003e\n \u003cp\u003e29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.606911447084233%\" valign=\"top\"\u003e\n \u003cp\u003e36\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.550755939524837%\" valign=\"top\"\u003e\n \u003cp\u003e49\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"11.01511879049676%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e10.\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"24.838012958963283%\" valign=\"top\"\u003e\n \u003cp\u003e4j\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23110151187905%\" valign=\"top\"\u003e\n \u003cp\u003e-2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.879049676025918%\" valign=\"top\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.879049676025918%\" valign=\"top\"\u003e\n \u003cp\u003e30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.606911447084233%\" valign=\"top\"\u003e\n \u003cp\u003e33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.550755939524837%\" valign=\"top\"\u003e\n \u003cp\u003e44\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"11.01511879049676%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e11.\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"24.838012958963283%\" valign=\"top\"\u003e\n \u003cp\u003e4k\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23110151187905%\" valign=\"top\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.879049676025918%\" valign=\"top\"\u003e\n \u003cp\u003e25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.879049676025918%\" valign=\"top\"\u003e\n \u003cp\u003e50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.606911447084233%\" valign=\"top\"\u003e\n \u003cp\u003e65\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.550755939524837%\" valign=\"top\"\u003e\n \u003cp\u003e80\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"11.01511879049676%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e12.\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"24.838012958963283%\" valign=\"top\"\u003e\n \u003cp\u003e4l\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23110151187905%\" valign=\"top\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.879049676025918%\" valign=\"top\"\u003e\n \u003cp\u003e24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.879049676025918%\" valign=\"top\"\u003e\n \u003cp\u003e41\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.606911447084233%\" valign=\"top\"\u003e\n \u003cp\u003e61\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.550755939524837%\" valign=\"top\"\u003e\n \u003cp\u003e59\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"11.01511879049676%\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e13.\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"24.838012958963283%\" valign=\"top\"\u003e\n \u003cp\u003eNaproxen\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.23110151187905%\" valign=\"top\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.879049676025918%\" valign=\"top\"\u003e\n \u003cp\u003e32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.879049676025918%\" valign=\"top\"\u003e\n \u003cp\u003e53\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.606911447084233%\" valign=\"top\"\u003e\n \u003cp\u003e67\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.550755939524837%\" valign=\"top\"\u003e\n \u003cp\u003e79\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e"},{"header":"Material \u0026 Method","content":"\u003cp\u003eOnly analytical-grade chemicals and solvents were utilised. All chemicals came from Sigma-Aldrich, India. A UV-lit spot on pre-coated silica gel plates (TLC silica gel) assessed the purity of all chemicals. In a chloroform: ethanol (10:1) solvent solution, TLC monitored reaction completion. The Stuart SMP30 melting point device recorded uncorrected melting points. The elemental analyses were recorded on Perkin-Elmer 240Bs. Chemical shifts were measured in parts per million (\u0026delta;) units using tetramethylsilane as an internal reference, using SHIMADZU (Japan) IR and Bruker Advance Neo 500 MHz NMR spectrophotometers. Mass spectrum data were collected using synapt-XS#DBA064 (Water Corporation).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eGeneral procedure for the synthesis of\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003e8-ethyl-5-oxo-2-(piperazin-1-yl)-5,8-dihydropyrido[2,3-\u003cem\u003ed\u003c/em\u003e]pyrimidine-6-carboxylate (2)\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA mixture of compound \u003cstrong\u003e(1)\u003c/strong\u003e (1.5 g, 0.0051mol) in ethanol (20 ml) was refluxed in the presence of conc. sulphuric acid (1 ml) for 7 hours. After the reaction was complete, the mixture was carefully poured into ice water. To neutralise the excess acid, a sodium bicarbonate solution was added. The resulting solid was then filtered and washed with water. This process yielded white crystals, with a melting point of 236-238\u0026deg;C, and a yield of 73%.\u003cstrong\u003e\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSynthesis of 8-ethyl-5-oxo-2-(piperazin-1-yl)-5,8-dihydropyrido[2,3-\u003cem\u003ed\u003c/em\u003e]pyrimidine-6-carbohydrazide (3)\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA mixture of comnpound \u003cstrong\u003e(2)\u003c/strong\u003e 0.3 g (0.0015 mol) and hydrazine hydrate (5 ml) in methanol (6 ml) was refluxed for 7 hours. Then reaction mixture was concentrated and left for cool.\u0026nbsp;Finally, ethanol was used to filter and recrystallize the off-white solid into white crystals (3). Yield: 67%, m.p. 241-244˯C. TLC methanol: chloroform (7:3).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSynthesis of 8-ethyl-2-(piperazin-1-yl)-6-(1,3,4-oxadiazol-2-yl)pyrido[2,3-d]pyrimidin-5(8\u003cem\u003eH\u003c/em\u003e)-one (4)\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAn equimolar concentration of compound \u003cstrong\u003e3\u003c/strong\u003e (0.211g, 0.01mol) and 4-nitro benzoic acid (0.111g, 0.01 mol) was refluxed with\u0026nbsp;phosphorous oxychloride (4ml). For 2 hours, the reaction mixture was refluxed at 100˚C. The surplus POCl3 was concentrated under high vacuum after cooling the reaction mixture to room temperature. TLC analysed the reaction. Also, surplus POCl3 was distilled under lower pressure. The reaction material was agitated and placed into ice-cold water after cooling. After separation, the solid was filtered and washed with sodium bicarbonate and water. Recrystallizing with ethanol yielded dark crystalline solids of the final compound (4).\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e8-ethyl-6-(5-(4-nitrophenyl)-1,3,4-oxadiazol-2-yl)-2-(piperazin-1-yl)pyrido[2,3-d]pyrimidin-5(8H)-one \u003cstrong\u003e(4a)\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eReddish brown color solid, yield (66%), m.p. 238-240\u0026nbsp;\u003cspan dir=\"RTL\"\u003e֯\u003c/span\u003eC. IR (KBr, cm\u003csup\u003e-1\u003c/sup\u003e): 3432.27 (NH str): 3113.61(-CH\u003csub\u003e\u0026nbsp;\u003c/sub\u003estr aromatic): 1694.75 (C=O str): 1610.52 (C=C str): 1525 (NO\u003csub\u003e2\u003c/sub\u003e str): 1434.72 (C=N str): 1108.25 (C-O-C str): 1257.60 (C-N str): 2923.71 (C-H aliphatic str); \u003csup\u003e1\u003c/sup\u003eH NMR (500 MHz, DMSO) \u0026delta; ppm: 8.1, 8.3 (m, 4H, aromatic hydrogen), 1.22 (t, 3H, -CH\u003csub\u003e3\u003c/sub\u003e), 1.45 (NH, piperazine ring), 7.7 (s, 1H, CH at C-7), 2.5 \u0026amp; 3.3 (m, 8H,-CH\u003csub\u003e2\u003c/sub\u003e piperazine ring), 4.1 (m, -CH\u003csub\u003e2\u003c/sub\u003e ethyl), 7.2 (s, CH at C-4), TOF MS ES\u003csup\u003e+\u003c/sup\u003e(m/z): 448 M\u003csup\u003e+\u003c/sup\u003e, other fragments are 326 m\u003csup\u003e+\u003c/sup\u003e, 258 m\u003csup\u003e+\u003c/sup\u003e; CHN Analysis calcted (%) for C\u003csub\u003e21\u003c/sub\u003eH\u003csub\u003e19\u003c/sub\u003eN\u003csub\u003e8\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e: C, 56.25; H, 4.50; N, 24.99 found: C, 56.55; H, 4.80; N, 24.59.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e6-(5-(4-chlorophenyl)-1,3,4-oxadiazol-2-yl)-8-ethyl-2-(piperazin-1-yl)pyrido[2,3-d]pyrimidin-5(8H)-one \u003cstrong\u003e(4b)\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eDark brown color solid, yield (68%), m.p. 253-255\u0026nbsp;\u003cspan dir=\"RTL\"\u003e֯\u003c/span\u003eC; IR (KBr, cm\u003csup\u003e-1\u003c/sup\u003e): 3427.52 (NH str): 3243.95 (-CH\u003csub\u003e\u0026nbsp;\u003c/sub\u003estr aromatic): 1717.26 (C=O str): 1636.18 (C=C str): 738.40 (C-Cl str): 1477.23 (C=N str): 1091.32 (C-O-C str): 1385.55 (C-N str): 2926.69 (C-H aliphatic str); \u003csup\u003e1\u003c/sup\u003eH NMR (500 MHz, DMSO) \u0026delta; ppm: 7.9, 7.2 (m, 4H, aromatic hydrogen), 1.4 (t, 3H, -CH\u003csub\u003e3\u003c/sub\u003e), 1.22 (NH piperazine ring), 7.5 (s, 1H, CH at C-4), 2.5, 3.4 (m, 8H, -CH\u003csub\u003e2\u003c/sub\u003e piperazine ring), 4.4 (m, -CH\u003csub\u003e2\u003c/sub\u003e ethyl), 8.3 (s, CH at C-7), TOF MS ES\u003csup\u003e+\u003c/sup\u003e 437 M\u003csup\u003e+\u003c/sup\u003e, other fragments are 326 m\u003csup\u003e+\u003c/sup\u003e, 293 m\u003csup\u003e+\u003c/sup\u003e, 258 m\u003csup\u003e+\u003c/sup\u003e; CHN Analysis calcted (%) for C\u003csub\u003e21\u003c/sub\u003eH\u003csub\u003e19\u003c/sub\u003eN\u003csub\u003e7\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003eCl: C, 57.60; H, 4.60; N, 22.39 found: C, 57.20; H, 4.20; N, 21.45.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e8-ethyl-6-(5-(4-hydroxyphenyl)-1,3,4-oxadiazol-2-yl)-2-(piperazin-1-yl)pyrido[2,3-d]pyrimidin-5(8H)-one \u003cstrong\u003e(4c)\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eDark brown color solid, yield (65%), m.p. 258-260\u0026nbsp;\u003cspan dir=\"RTL\"\u003e֯\u003c/span\u003eC; IR (KBr, cm\u003csup\u003e-1\u003c/sup\u003e): 3550.90 (C-OH): 3474.36 (NH str): 3167.16 (-CH\u003csub\u003e\u0026nbsp;\u003c/sub\u003estr aromatic): 1636.66 (C=C str): 1617.59 (C=O str): 1449.67 (C=N str): 1061.38 (C-O-C str): 1383.15 (C-N str): 2926.97 (C-H aliphatic str); \u003csup\u003e1\u003c/sup\u003eH NMR (500 MHz, DMSO) \u0026delta; ppm: 7.8, 6.5 (m, 4H, aromatic hydrogen), 9.2 (s, -OH), 1.4 (t, 3H, -CH\u003csub\u003e3\u003c/sub\u003e), 1.1 (NH piperazine ring), 7.4 (s, 1H, CH at C-4), 2.40, 3.46 (m, 8H, -CH\u003csub\u003e2\u003c/sub\u003e piperazine ring), 7.1 (s, CH at C-7), 4.4 (m, -CH\u003csub\u003e2\u003c/sub\u003e ethyl), TOF MS ES\u003csup\u003e+\u003c/sup\u003e 420 M\u003csup\u003e+\u003c/sup\u003e, other fragments are 326 m\u003csup\u003e+\u003c/sup\u003e, 258 m\u003csup\u003e+\u003c/sup\u003e; CHN Analysis calcted (%) for C\u003csub\u003e21\u003c/sub\u003eH\u003csub\u003e20\u003c/sub\u003eN\u003csub\u003e7\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e: C, 60.13; H, 5.05; N, 23.38 found: C, 60.43; H, 5.25; N, 23.18.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e6-(5-(4-aminophenyl)-1,3,4-oxadiazol-2-yl)-8-ethyl-2-(piperazin-1-yl)pyrido[2,3-d]pyrimidin-5(8H)-one \u003cstrong\u003e(4d)\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eReddish brown color solid, yield (63%), m.p. 264-267\u0026nbsp;\u003cspan dir=\"RTL\"\u003e֯\u003c/span\u003eC; IR (KBr, cm\u003csup\u003e-1\u003c/sup\u003e): 3459.34 (C-NH\u003csub\u003e2\u003c/sub\u003e): 3416.25 (NH str): 3127.17 (-CH\u003csub\u003e\u0026nbsp;\u003c/sub\u003estr aromatic): 1620.22 (C=O str): 1633.97 (C=C str): 1383.39 (C=N str): 1089.15 (C-O-C str): 1383.39 (C-N str): 2923.58 (C-H aliphatic str); \u003csup\u003e1\u003c/sup\u003eH NMR (500 MHz, DMSO) \u0026delta; ppm: 7.8, 6.6 (m, 4H, aromatic hydrogen), 5.5 (s, -NH\u003csub\u003e2\u003c/sub\u003e), 1.53 (t, 3H, -CH\u003csub\u003e3\u003c/sub\u003e), 1.27 (NH piperazine ring), 2.5, 3.4 (m, 8H, -CH\u003csub\u003e2\u003c/sub\u003e piperazine ring), 7.8 (s, -CH at C-4), 7.4 (s, -CH at C-7), 4.1 (m, -CH\u003csub\u003e2\u003c/sub\u003e ethyl), TOF MS ES\u003csup\u003e+\u003c/sup\u003e 418 M\u003csup\u003e+\u003c/sup\u003e, other fragments are 327 m\u003csup\u003e+\u003c/sup\u003e, 257 m\u003csup\u003e+\u003c/sup\u003e; CHN Analysis calcted (%) for C\u003csub\u003e21\u003c/sub\u003eH\u003csub\u003e21\u003c/sub\u003eN\u003csub\u003e8\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e: C, 60.28; H, 5.30; N, 26.78 found: C, 60.48; H, 5.50; N, 26.38.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e8-ethyl-6-(5-(4-methoxyphenyl)-1,3,4-oxadiazol-2-yl)-2-(piperazin-1-yl)pyrido[2,3-d]pyrimidin-5(8H)-one \u003cstrong\u003e(4e)\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eLight brown color solid, yield (60%), m.p. 248-252\u0026nbsp;\u003cspan dir=\"RTL\"\u003e֯\u003c/span\u003eC; IR (KBr, cm\u003csup\u003e-1\u003c/sup\u003e): 3433.55 (NH str): 2925 (aliphatic, C-H), 1113 (aliphatic C-O linkage) 3160.12 (-CH\u003csub\u003e\u0026nbsp;\u003c/sub\u003estr aromatic): 1623.27 (C=C str): 1692.11 (C=O str): 1444.19 (C=N str): 1062.73 (C-O-C str): 1382.77 (C-N str): 2852.74 (C-H aliphatic str); \u003csup\u003e1\u003c/sup\u003eH NMR (500 MHz, DMSO) \u0026delta; ppm: 8.1, 7.0 (m, 4H, aromatic hydrogen), 3.8 (s, 3H, O-CH\u003csub\u003e3\u003c/sub\u003e), 1.4 (t, 3H, -CH\u003csub\u003e3\u003c/sub\u003e), 1.2 (NH piperazine ring), 3.2, 2.5 (m, 8H, -CH\u003csub\u003e2\u003c/sub\u003e piperazine), 7.4 (s, -CH at C-7), 4.3 (m, -CH\u003csub\u003e2\u003c/sub\u003e ethyl), 7.7 (s, -CH at C-4), TOF MS ES\u003csup\u003e+\u003c/sup\u003e 434 M\u003csup\u003e+\u003c/sup\u003e, other fragments are 418 m\u003csup\u003e+\u003c/sup\u003e, 326 m\u003csup\u003e+\u003c/sup\u003e, 284 m\u003csup\u003e+\u003c/sup\u003e; CHN Analysis calcted (%) for C\u003csub\u003e22\u003c/sub\u003eH\u003csub\u003e22\u003c/sub\u003eN\u003csub\u003e7\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e: C, 60.96; H, 5.35; N, 22.62; found: C, 60.45; H, 5.65; N, 22.12.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e8-ethyl-6-(5-(2-fluorophenyl)-1,3,4-oxadiazol-2-yl)-2-(piperazin-1-yl)pyrido[2,3-d]pyrimidin-5(8H)-one \u003cstrong\u003e(4f)\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eReddish brown color solid,\u0026nbsp;yield\u0026nbsp;(62%), m.p. 253-256\u0026nbsp;\u003cspan dir=\"RTL\"\u003e֯\u003c/span\u003eC; IR (KBr, cm\u003csup\u003e-1\u003c/sup\u003e): 3360.50 (NH str): 3243.95 (-CH\u003csub\u003e\u0026nbsp;\u003c/sub\u003estr aromatic): 1720.16 (C=O str): 1635.15 (C=C str): 1220.12 (C-F str): 1470.23 (C=N str): 1110.32 (C-O-C str): 1385.55 (C-N str): 2914.64 (C-H aliphatic str); \u003csup\u003e1\u003c/sup\u003eH NMR (500 MHz, DMSO) \u0026delta; ppm: 8.3, 7.9, 7.3 (m, 4H, aromatic hydrogen), 1.4 (t, 3H, -CH\u003csub\u003e3\u003c/sub\u003e), 1.1 (NH piperazine ring), 7.7 (s, 1H, -CH at C-4), 2.5, 3.2 (m, 8H, -CH\u003csub\u003e2\u003c/sub\u003e piperazine ring), 7.5 (s, -CH at C-7), 4.1 (m, -CH\u003csub\u003e2\u003c/sub\u003e ethyl), TOF MS ES\u003csup\u003e+\u003c/sup\u003e 420 M\u003csup\u003e+\u003c/sup\u003e, other fragments are 327 m\u003csup\u003e+\u003c/sup\u003e, 258 m\u003csup\u003e+\u003c/sup\u003e; CHN Analysis calcted (%) for C\u003csub\u003e21\u003c/sub\u003eH\u003csub\u003e19\u003c/sub\u003eN\u003csub\u003e7\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003eF: C, 59.85; H, 4.78; N, 23.27 found: C, 59.65; H, 4.28; N, 23.17.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e8-ethyl-6-(5-(4-fluorophenyl)-1,3,4-oxadiazol-2-yl)-2-(piperazin-1-yl)pyrido[2,3-d]pyrimidin-5(8H)-one \u003cstrong\u003e(4g)\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eReddish brown color solid,\u0026nbsp;yield\u0026nbsp;(62%), m.p. 253-256\u0026nbsp;\u003cspan dir=\"RTL\"\u003e֯\u003c/span\u003eC; IR (KBr, cm\u003csup\u003e-1\u003c/sup\u003e): 3360.50 (NH str): 3243.95 (-CH\u003csub\u003e\u0026nbsp;\u003c/sub\u003estr aromatic): 1720.16 (C=O str): 1635.15 (C=C str): 1220.12 (C-F str): 1470.23 (C=N str): 1110.32 (C-O-C str): 1385.55 (C-N str): 2916.64 (C-H aliphatic str); \u003csup\u003e1\u003c/sup\u003eH NMR (500 MHz, DMSO) \u0026delta; ppm: 8.3, 7.3 (m, 4H, aromatic hydrogen), 1.43 (t, 3H, -CH\u003csub\u003e3\u003c/sub\u003e), 1.15 (NH piperazine ring), 3.2, 2.5 (m, 8H, -CH\u003csub\u003e2\u003c/sub\u003e piperazine ring), 7.7 (s, -CH at C-4), 7.5 (s, -CH at C-7) TOF MS ES\u003csup\u003e+\u003c/sup\u003e 420 M\u003csup\u003e+\u003c/sup\u003e, other fragments are 327 m\u003csup\u003e+\u003c/sup\u003e, 304 m\u003csup\u003e+\u003c/sup\u003e, 258 m\u003csup\u003e+\u003c/sup\u003e; CHN Analysis calcted (%) for C\u003csub\u003e21\u003c/sub\u003eH\u003csub\u003e19\u003c/sub\u003eN\u003csub\u003e7\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003eF: C, 59.85; H, 4.78; N, 23.27 found: C, 58.23; H, 4.26; N. 22.98.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e6-(5-(2-chlorophenyl)-1,3,4-oxadiazol-2-yl)-8-ethyl-2-(piperazin-1-yl)pyrido[2,3-d]pyrimidin-5(8H)-one \u003cstrong\u003e(4h)\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eDark brown color solid,\u0026nbsp;yield\u0026nbsp;(68%), m.p. 253-255\u0026nbsp;\u003cspan dir=\"RTL\"\u003e֯\u003c/span\u003eC; IR (KBr, cm\u003csup\u003e-1\u003c/sup\u003e): 3427.52 (NH str): 3245.95 (-CH\u003csub\u003e\u0026nbsp;\u003c/sub\u003estr aromatic): 1717.26 (C=O str): 1636.18 (C=C str): 738.40 (C-Cl str): 1477.23 (C=N str): 1091.32 (C-O-C str): 1385.55 (C-N str): 2925.59 (C-H aliphatic str); \u003csup\u003e1\u003c/sup\u003eH NMR (500 MHz, DMSO) \u0026delta; ppm: 7.8, 7.7, 7.3 (m, 1H, aromatic hydrogen), 1.4 (t, 3H, -CH\u003csub\u003e3\u003c/sub\u003e), 1.1 (NH piperazine ring), 3.2, 2.6 (m CH\u003csub\u003e2\u003c/sub\u003e piperazine), 7.5 (s, CH at C-7) 7.6 (s, CH at C-4), 4.1 (m, -CH\u003csub\u003e2\u003c/sub\u003e ethyl), TOF MS ES\u003csup\u003e+\u003c/sup\u003e 437 M\u003csup\u003e+\u003c/sup\u003e, other fragments are 326 m\u003csup\u003e+\u003c/sup\u003e, 293 m\u003csup\u003e+\u003c/sup\u003e, 258 m\u003csup\u003e+\u003c/sup\u003e; CHN Analysis calcted (%) for C\u003csub\u003e21\u003c/sub\u003eH\u003csub\u003e19\u003c/sub\u003eN\u003csub\u003e7\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003eCl: C, 57.60; H, 4.60; N, 22.39 found: C, 57.45; H, 4.22; N, 22.64.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e8-ethyl-2-(piperazin-1-yl)-6-(5-(3,4,5-trimethoxyphenyl)-1,3,4-oxadiazol-2-yl)pyrido[2,3-d]pyrimidin-5(8H\u0026shy;\u0026shy;\u0026shy;)-one \u003cstrong\u003e(4i)\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eLight brown color solid, yield (60%), m.p. 248-252\u0026nbsp;\u003cspan dir=\"RTL\"\u003e֯\u003c/span\u003eC; IR (KBr, cm\u003csup\u003e-1\u003c/sup\u003e): 3430.35 (NH str): 2925 (aliphatic, C-H), 2950 (\u003cem\u003epara\u003c/em\u003e-OCH\u003csub\u003e3\u003c/sub\u003e), 2840.24, 2852.74 (\u003cem\u003emeta\u003c/em\u003e-OCH\u003csub\u003e3\u003c/sub\u003e) 1113 (aliphatic C-O linkage) 3160.12 (-CH\u003csub\u003e\u0026nbsp;\u003c/sub\u003estr aromatic): 1623.27 (C=C str): 1692.11 (C=O str): 1440.29 (C=N str): 1062.73 (C-O-C str): 1382.77 (C-N str): 2852.74 (C-H aliphatic str); \u003csup\u003e1\u003c/sup\u003eH NMR (500 MHz, DMSO) \u0026delta; ppm: 7.3 (s, 2H, aromatic hydrogen), 3.7 (s, 3H, \u003cem\u003epara\u003c/em\u003e, O-CH\u003csub\u003e3\u003c/sub\u003e), 3.9 (s, 6H, \u003cem\u003emeta\u003c/em\u003e, O-CH\u003csub\u003e3\u003c/sub\u003e) \u0026nbsp;1.4 (t, 3H, -CH\u003csub\u003e3\u003c/sub\u003e), 1.1 (NH piperazine ring), 3.2, 2.6 (m, 8H, -CH\u003csub\u003e2\u003c/sub\u003e piperazine), 7.5 (s, -CH at C-7), 4.2 (m, -CH\u003csub\u003e2\u003c/sub\u003e ethyl), 7.7 (s, -CH at C-4), TOF MS ES\u003csup\u003e+\u003c/sup\u003e 493 M\u003csup\u003e+\u003c/sup\u003e, other fragments are 448 m\u003csup\u003e+\u003c/sup\u003e, 326 m\u003csup\u003e+\u003c/sup\u003e, 284 m\u003csup\u003e+\u003c/sup\u003e; CHN Analysis calcted (%) for C\u003csub\u003e24\u003c/sub\u003eH\u003csub\u003e22\u003c/sub\u003eN\u003csub\u003e7\u003c/sub\u003eO\u003csub\u003e5\u003c/sub\u003e: C, 58.41; H, 5.51; N, 19.87 found: C, 58.62; H, 5.44; N, 20.02.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e6-(5-(2,4-dichlorophenyl)-1,3,4-oxadiazol-2-yl)-8-ethyl-2-(piperazin-1-yl)pyrido[2,3-d]pyrimidin-5(8H)-one \u003cstrong\u003e(4j)\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eDark brown color solid, yield (68%), m.p. 253-255\u0026nbsp;\u003cspan dir=\"RTL\"\u003e֯\u003c/span\u003eC; IR (KBr, cm\u003csup\u003e-1\u003c/sup\u003e): 3427.52 (NH str): 3243.95 (-CH\u003csub\u003e\u0026nbsp;\u003c/sub\u003estr aromatic): 1717.26 (C=O str): 1636.18 (C=C str): 740.26 (C-Cl str): 1477.23 (C=N str): 1091.32 (C-O-C str): 1385.55 (C-N str): 2926.69 (C-H aliphatic str); \u003csup\u003e1\u003c/sup\u003eH NMR (500 MHz, DMSO) \u0026delta; ppm: 7.3, 7.7, 7.8 (s, 3H, aromatic hydrogen), 1.4 (t, 3H, -CH\u003csub\u003e3\u003c/sub\u003e), 1.1 (NH piperazine ring), 7.5 (s, 1H, -CH at C-4), 2.6, 3.2 (m, 8H, -CH\u003csub\u003e2\u003c/sub\u003e piperazine ring), 4.1 (m, -CH\u003csub\u003e2\u003c/sub\u003e ethyl), 7.6 (s, -CH at C-7), TOF MS ES\u003csup\u003e+\u003c/sup\u003e 472 M\u003csup\u003e+\u003c/sup\u003e, other fragments are 400 m\u003csup\u003e+\u003c/sup\u003e, 326 m\u003csup\u003e+\u003c/sup\u003e, 293 m\u003csup\u003e+\u003c/sup\u003e, 258 m\u003csup\u003e+\u003c/sup\u003e; CHN Analysis calcted (%) for C\u003csub\u003e21\u003c/sub\u003eH\u003csub\u003e18\u003c/sub\u003eN\u003csub\u003e7\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003eCl\u003csub\u003e2\u003c/sub\u003e: C, 53.40; H, 4.05; N, 20.76 found: C, 53.60; H, 4.15; N, 20.46. \u0026nbsp;\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e8-ethyl-2-(piperazin-1-yl)-6-(5-(m-tolyl)-1,3,4-oxadiazol-2-yl)pyrido[2,3-d]pyrimidin-5(8H)-one \u003cstrong\u003e(4k)\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eReddish brown color solid, yield (62%), m.p. 253-256\u0026nbsp;\u003cspan dir=\"RTL\"\u003e֯\u003c/span\u003eC; IR (KBr, cm\u003csup\u003e-1\u003c/sup\u003e): 3355.30 (NH str): 3250.90 (-CH\u003csub\u003e\u0026nbsp;\u003c/sub\u003estr aromatic): 1718.26 (C=O str): 1635.15 (C=C str): 1220.12 (C-F str): 1465.26 (C=N str): 1110.32 (C-O-C str): 1385.55 (C-N str): 2920.14 (C-H aliphatic str); \u003csup\u003e1\u003c/sup\u003eH NMR (500 MHz, DMSO) \u0026delta; ppm: 8.0, 7.7, 7.3, 7.0 (m, 4H, aromatic hydrogen), 1.4 (t, 3H, -CH\u003csub\u003e3\u003c/sub\u003e), 1.1 (NH piperazine ring), 7.7 (s, 1H, -CH at C-4), 2.4 (s, 3H, phenyl \u0026ndash;CH\u003csub\u003e3\u003c/sub\u003e), 2.7, 3.2 (m, -CH\u003csub\u003e2\u003c/sub\u003e piperazine ring), 7.6 (s, -CH at C-7), 4.1 (m, -CH\u003csub\u003e2\u003c/sub\u003e ethyl), TOF MS ES\u003csup\u003e+\u003c/sup\u003e 417 M\u003csup\u003e+\u003c/sup\u003e, other fragments are 400 m\u003csup\u003e+\u003c/sup\u003e, 326 m\u003csup\u003e+\u003c/sup\u003e, 293 m\u003csup\u003e+\u003c/sup\u003e, 258 m\u003csup\u003e+\u003c/sup\u003e; CHN Analysis calcted (%) for C\u003csub\u003e22\u003c/sub\u003eH\u003csub\u003e22\u003c/sub\u003eN\u003csub\u003e7\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e: C, 63.30; H, 5.55; N, 23.49; found: C, 63.25; H, 5.25; N, 23.69.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e8-ethyl-2-(piperazin-1-yl)-6-(5-(p-tolyl)-1,3,4-oxadiazol-2-yl)pyrido[2,3-d]pyrimidin-5(8H)-one \u003cstrong\u003e(4l)\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eReddish brown color solid, yield (62%), m.p. 260-262\u0026nbsp;\u003cspan dir=\"RTL\"\u003e֯\u003c/span\u003eC; IR (KBr, cm\u003csup\u003e-1\u003c/sup\u003e): 3390.20 (NH str): 3250.90 (-CH\u003csub\u003e\u0026nbsp;\u003c/sub\u003estr aromatic): 1718.26 (C=O str): 1635.15 (C=C str): 1220.12 (C-F str): 1465.26 (C=N str): 1110.32 (C-O-C str): 1385.55 (C-N str): 2925.34 (C-H aliphatic str); \u003csup\u003e1\u003c/sup\u003eH NMR (500 MHz, DMSO) \u0026delta; ppm: 8.0, 7.3 (m, 4H, aromatic hydrogen), 1.26 (t, 3H, -CH\u003csub\u003e3\u003c/sub\u003e), 1.4 (NH piperazine ring), 7.7 (s, 1H, -CH at C-4), 2.4 (s, 3H, phenyl \u0026ndash;CH\u003csub\u003e3\u003c/sub\u003e), 2.7, 3.2 (m, 8H, -CH\u003csub\u003e2\u003c/sub\u003e piperazine ring), 7.5 (s, -CH at C-7), 4.1 (m, -CH\u003csub\u003e2\u003c/sub\u003e ethyl), TOF MS ES\u003csup\u003e+\u003c/sup\u003e 417 M\u003csup\u003e+\u003c/sup\u003e, other fragments are 400 m\u003csup\u003e+\u003c/sup\u003e, 326 m\u003csup\u003e+\u003c/sup\u003e, 293 m\u003csup\u003e+\u003c/sup\u003e, 258 m\u003csup\u003e+\u003c/sup\u003e; CHN Analysis calcted (%) for C\u003csub\u003e22\u003c/sub\u003eH\u003csub\u003e22\u003c/sub\u003eN\u003csub\u003e7\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e: C, 63.30; H, 5.55; N, 23.49; found: C, 63.10; H, 5.25; N, 23.29.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDocking Methodology\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003e(i) Ligand and Protein preparation:\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA library of fifty quinolone substituted 1,3,4-oxadiazole derivatives\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e(4a-l)\u0026nbsp;were prepared in Chem draw professional 15 by exploring the quinolone-based literatures from various sources. These ligands (4a-l) were included to the ligand library in an attempt to determine the most prominent lead derivative responsible for the development of significant antibacterial quinolone with the ease of developing the most probable substitution involved in the inhibition of bacterial DNA synthesis [26]. Furthermore, the macromolecular target involved in bacterial\u0026nbsp;DNA transcription and replication processes\u0026nbsp;was also explored from various quinolone literature. It has been observed that the DNA gyrase as essential bacterial enzyme which actively involved in bacterial DNA synthesis. Therefore, the complex co-crystallized structure of DNA gyrase (\u003cem\u003etopoisomerase II\u003c/em\u003e) as target sites (\u003cem\u003egram +ve\u003c/em\u003e \u0026amp; \u003cem\u003egram\u003c/em\u003e \u003cem\u003e-ve\u003c/em\u003e) with \u003cem\u003eCOX-II\u003c/em\u003e were retrieved from protein databank i.e. \u003cem\u003egram\u003c/em\u003e \u003cem\u003e+ve\u003c/em\u003e (PDB id: 2w9s \u0026amp; 1yzf), \u003cem\u003egram\u003c/em\u003e \u003cem\u003e\u0026ndash;ve\u003c/em\u003e (PDB id: 6cqa \u0026amp; 6m1j) and 5ikr. All the target structures were downloaded in .Pdb format and pre-processed by adding\u0026nbsp;hydrogens with gasteiger charges. Further water molecules were deleted and saved it in\u0026nbsp;PDBQT format [27].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eii) Molecular Docking Studies\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAfter the successfully preparation of ligand and protein structures with proper selection of grid parameters rigid docking of ligands at defined pockets of DNA gyrase and \u003cem\u003eCOX-II\u003c/em\u003e target site was performed in Autodock format. Thereafter, best nine poses were obtained as output which confirmed the best binding interaction of docked ligands at target sites. We were able to choose the optimal ligand pose at the target site by carefully examining the binding interactions and dock scores among these poses [28].\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAntibacterial \u0026nbsp;\u0026amp; Antifungal activity\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe antimicrobial efficacy of the quinolone derivatives (4a-l) were assessed using the MTT assay [29], following established protocols for antimycobacterial activity evaluation. In a 96-well flat-bottom plate, each quinolone derivative was subjected to two-fold serial dilution using sterile distilled water. Subsequently, test strains of \u003cem\u003eStaphylococcus aureus\u003c/em\u003e (ATCC 25923), \u003cem\u003eEnterococcus faecalis\u003c/em\u003e (ATCC 29212), \u003cem\u003eEscherichia coli\u0026nbsp;\u003c/em\u003e(ATCC 25922), \u003cem\u003ePseudomonas aeruginosa\u003c/em\u003e (27853) and \u003cem\u003ecandida albicans\u003c/em\u003e (ATCC 10231) were adjusted to a McFarland standard of 0.5, and 100 \u0026micro;L of the bacterial and fungal suspensions were added to each well separately in three replicates using a micropipette. The concentrations of the quinolone derivatives tested ranged from 2.5 to 640 \u0026micro;g/mL. As controls, wells containing bacterial growth without treatment, bacterial growth treated with Pipemidic acid, and bacterial growth treated with the antibiotic Ciprofloxacin were utilized as negative and positive controls, respectively. For the antifungal activity, synthesized quinolone substituted 1,3,4-oxadiazole derivatives\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e(4a-l) were assessed using the MTT assay against \u003cem\u003eCandida albicans\u0026nbsp;\u003c/em\u003e(ATCC 10231) and fluconazole was used as reference positive control. The plates were covered, placed in zip-lock plastic bags, and incubated at 37\u0026deg;C for 24 hours. Following the incubation period, 20 \u0026micro;L of a 5 mg/mL MTT dye solution was added and left to incubate in the dark at 37\u0026deg;C for 4 hours. Afterwards, the supernatant was discarded, and the formazan precipitate was dissolved in dimethyl sulfoxide (DMSO). The plates were re-incubated for an additional 30 minutes, and absorbance was measured at 570 nm using a Spectramax spectrophotometer. The color change in the wells containing DMSO was indicative of the presence of viable cells, with violet color signifying bacterial growth and yellow color indicating the absence of viable cells.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eBiological screening\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAnimals\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe Institutional Animal Ethical Committee approved the protocol for conducting the experiment (Registration No MMCP-IAEC-90). Wistar rats of either sex weighing 200-250 gm were used for the anti-inflammatory investigation. They had unrestricted access to water, a typical diet, and a standard facility.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcute toxicological study\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAcute toxicity was investigated, and the safe dose was determined using OECD test guideline 425 [30].\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAnti-inflammatory activity\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAnimals were grouped. Each group has six animals. The anti-inflammatory effect of the test compounds was tested using carrageenan-induced paw oedema in rats [31]. Different groups of rats received 50 mg/kg oral pre-treatment. Each rat received 0.1 ml of 1% carrageenan suspension into the sub-plantar region of its left hind paw after 1 hour to produce oedema. A plethysmometer (Laboratory enterprises, Nasik) was used to assess paw volume at 0, 1, 2, 3, and 4 hours. Naproxen (50 mg/kg p.o.) was standard. Mean \u0026plusmn; SEM is determined and compared for treated and control animals at each time interval for statistical analysis.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eNovel synthesized quinolone derivatives (4a-l) were designed, synthesized, and characterized using different spectroscopic techniques. All the synthesized hybrid molecules were evaluated for their antimicrobial and \u003cem\u003ein vivo\u003c/em\u003e anti-inflammatory activities. Compounds 4f, 4h \u0026amp; 4k showed potent hybrid with maximum antibacterial activity against \u003cem\u003eStaphylococcus aureus\u003c/em\u003e, \u003cem\u003eEscherichia coli\u003c/em\u003e and \u003cem\u003ePseudomonas aeruginosa\u003c/em\u003e with MICs range of 8 \u0026micro;g/mL. Compound 4K exhibited potent anti-inflammatory activity which has a 3-amethylphenyl oxadiazole substitution on the C-6 position of pipemidic acid core structure and lacked antifungal efficacy against the candida albicans (ATCC 10231) fungal strain. Based on docking studies, the pipemidic acid substituted phenyl with oxadiazole functionality at position C-6 was actively implicated in a variety of binding interactions with the DNA gyrase active sites of bacterial strains including \u003cem\u003ePseudomonas aeruginosa\u003c/em\u003e, \u003cem\u003eEscherichia coli\u003c/em\u003e, and \u003cem\u003eStaphylococcus aureus\u003c/em\u003e. Understanding the interaction between various amino acids of the target protein sheds light on their ability to inhibit DNA gyrase. The study found that the presence of electron withdrawing and donating substitutions at the C-6 position resulted in improved antibacterial and anti-inflammatory activity. In summary, the study found that these hybrid compounds have the potential to be used in the future for creating antibacterial and anti-inflammatory agents.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eVishal Sharma: Design, Data Curation, Writing Dinesh Kumar Mehta: Data Curation, supervision Rina Das: Formal analysis \u0026nbsp;Diksha Sharma: Formal analysis\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u0026nbsp;\u003c/strong\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eZaman SB, Hussain MA, Nye R, Mehta V, Mamun KT, Hossain N (2017) A Review on Antibiotic Resistance: Alarm Bells are Ringing. 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Eur J Med Chem 247:115026. https://doi.org/10.1016/j.ejmech.2022.115026.\u003c/li\u003e\n\u003cli\u003eDhanawat M, Mehta DK and Das R (2021) An Elite Scaffold and a Wonderful Pharmacophore in Drug Discovery: Styrylquinoline. Mini Rev Med Chem 21:1849-1864. https://doi.org/10.2174/1389557521666210225115055.\u003c/li\u003e\n\u003cli\u003eSaini M, Das R, Mehta, DK, Chauhan S (2022) Styrylquinolines Derivatives: SAR Study and Synthetic Approaches. Med Chem 18:859-70. https://doi.org/10.2174/1573406418666220214085856.\u003c/li\u003e\n\u003cli\u003eSuree N, Jung ME, Clubb RT (2007) Recent advances towards new anti-infective agents that inhibit cell surface protein anchoring in Staphylococcus aureus and other gram-positive pathogens. Mini-Rev Med Chem 7:991-1000. \u003c/li\u003e\n\u003cli\u003eKashid BB, Salunkhe PH, Dongare BB, More KR, Khedkar VM, Ghanwat AA (2020) Synthesis of novel of 2, 5-disubstituted 1, 3, 4-oxadiazole derivatives and their in vitro anti-inflammatory, anti-oxidant evaluation, and molecular docking study. Bioorg Med Chem 30:127136. https://doi.org/10.1016/j.bmcl.2020.127136.\u003c/li\u003e\n\u003cli\u003eBadrinarayan P, Sastry GN (2012) Virtual filters for the design of type II p38 MAP kinase inhibitors: a fragment based library generation approach. J Mol Gr Model 34:89\u0026ndash;100. https://doi.org/10.1016/j.jmgm.2011.12.009.\u003c/li\u003e\n\u003cli\u003eGF Zhang, S Zhang, BF Pan, XF Liu, LS Feng (2018) 4-Quinolone derivatives and their activities against Gram-positive pathogens. Eur J Med Chem 143:710-723. https://doi.org/10.1016/j.ejmech.2017.11.082.\u003c/li\u003e\n\u003cli\u003eMcClendon AK, Osheroff N (2007) DNA topoisomerase II, genotoxicity, and cancer. Mutat Res Fundam Mol Muta 623:83-97. https://doi.org/10.1016/j.mrfmmm.2007.06.009.\u003c/li\u003e\n\u003cli\u003eHryhoriv H, Kovalenko SM, Georgiyants M, Sidorenko L, Georgiyants V (2023) A Comprehensive Review on Chemical Synthesis and Chemotherapeutic Potential of 3-Heteroaryl Fluoroquinolone Hybrids. Antibiotics 12:625. https://doi.org/10.3390/antibiotics12030625.\u003c/li\u003e\n\u003cli\u003eShah K, Mujwar S, (2022) Delineation of a Novel Non-Steroidal Anti-Inflammatory Drugs Derivative Using Molecular Docking and Pharmacological Assessment. Indian J Pharm Sci 84:642.\u003c/li\u003e\n\u003cli\u003eAllaka TR, Kummari B, Polkam N, Kuntala N, Chepuri K, Anireddy JS (2022) Novel heterocyclic 1, 3, 4-oxadiazole derivatives of fluoroquinolones as a potent antibacterial agent: Synthesis and computational molecular modeling. Molecular Diversity 26(3), 1581-1596. https://doi.org/10.1007/s11030-021-10287-3.\u003c/li\u003e\n\u003cli\u003eMahajan A, Singh H, Singh A, Agrawal DK, Arora A, Chundawat TS (2022) Trifluoromethylated quinolone-hydantoin hybrids: Synthesis and antibacterial evaluation. Sci 4:30. https://doi.org/10.3390/sci4030030.\u003c/li\u003e\n\u003cli\u003eRequena R, Vargas M, Chiralt A (2019) Study of the potential synergistic antibacterial activity of essential oil components using the thiazolyl blue tetrazolium bromide (MTT) assay. Lwt 101:183-190. https://doi.org/10.1016/j.lwt.2018.10.093.\u003c/li\u003e\n\u003cli\u003eOECD guidelines for the testing of chemicals: 425 Acute oral toxicity \u0026ndash; up-and-downprocedure (UDP), OECD (2008) 1\u0026ndash;27.\u003c/li\u003e\n\u003cli\u003eCA Winter, EA Risley, GW Nuss, Carrageenin-induced edema in hind paw of the rat as an assay for antiinflammatory drugs, Proc Soc Exp Biol Med 111:544\u0026ndash;547. https://doi.org/10.3181/00379727-111-27849.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Scheme ","content":"\u003cp\u003eScheme 1 is available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"molecular-diversity","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"modi","sideBox":"Learn more about [Molecular Diversity](http://link.springer.com/journal/11030)","snPcode":"11030","submissionUrl":"https://submission.nature.com/new-submission/11030/3","title":"Molecular Diversity","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Quinolone, Pipemidic acid, 1,3,4 oxadiazole, Antimicrobial, Anti-inflammatory, Binding energy ","lastPublishedDoi":"10.21203/rs.3.rs-4334362/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4334362/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eA novel series of quinolone-substituted 1,3,4-oxadiazole derivatives 4(a-l) have been designed and synthesized. The target compounds were investigated for their antibacterial activity against gram positive (\u003cem\u003eStaphylococcus aureus\u003c/em\u003e, ATCC 25923, \u003cem\u003eEnterococcus faecalis,\u003c/em\u003e ATCC 29212) and gram negative bacterium (\u003cem\u003eEscherichia coli\u003c/em\u003e, ATCC 25922, \u003cem\u003ePseudomonas aeruginosa\u003c/em\u003e, ATCC 27853) for antifungal activity using \u003cem\u003ecandida albicans \u003c/em\u003e(ATCC 10231) and anti-inflammatory activity as \u003cem\u003eCOX-II\u003c/em\u003e inhibitors, respectively. The 1,3,4-oxadiazole functionality was introduced at C-6 position of pipemidic acid derivatives. The structure of synthesized derivatives was confirmed by IR, \u003csup\u003e1\u003c/sup\u003eH NMR and Mass spectrometry techniques. The quinolone (pipemidic acid)-oxadiazole hybrid derivatives were found to be effective against bacterial strains. When compared to ciprofloxacin (MIC 16 µg/mL), the compounds under consideration (\u003cstrong\u003e4f, 4h, and 4k\u003c/strong\u003e) showed potent antibacterial activity against all bacterial strains except \u003cem\u003eEnterococcus faecalis\u003c/em\u003e, with MICs of 8 µg/mL. On the other hand, synthesized target compounds (4a–l) did not respond well\u0026nbsp;against the \u003cem\u003eCandida albicans\u003c/em\u003e fungal strain. The compound \u003cstrong\u003e(4k)\u003c/strong\u003e represents the high % inhibition against \u003cem\u003eCOX-II\u003c/em\u003e. The compounds \u003cstrong\u003e(4f, 4h \u0026amp; 4k)\u003c/strong\u003e exhibited the highest hydrogen bonding interaction with ARG57, ARG72, ARG78, LEU54 and MET16 target residues with a binding energy of -8.4, -8.6 \u0026amp; -8.5 kcal/mol into the active pocket of DNA gyrase enzyme respectively even better in comparison to reference ligands. Based on the docking study, the quinolone (pipemidic acid) oxadiazole hybrid structural ligands exhibited strong interaction at binding pockets of DNA gyrase enzyme.\u003c/p\u003e","manuscriptTitle":"Novel Quinolone substituted 1,3,4-oxadiazole derivatives: Design, synthesis, antimicrobial and anti-inflammatory potential","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-05-03 09:53:11","doi":"10.21203/rs.3.rs-4334362/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-05-19T13:05:55+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-04-29T16:20:24+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-04-28T07:15:58+00:00","index":"","fulltext":""},{"type":"submitted","content":"Molecular Diversity","date":"2024-04-27T13:51:37+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"molecular-diversity","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"modi","sideBox":"Learn more about [Molecular Diversity](http://link.springer.com/journal/11030)","snPcode":"11030","submissionUrl":"https://submission.nature.com/new-submission/11030/3","title":"Molecular Diversity","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"89cced5f-a111-4a9b-a4a4-28daad9de1f6","owner":[],"postedDate":"May 3rd, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-08-05T16:13:22+00:00","versionOfRecord":{"articleIdentity":"rs-4334362","link":"https://doi.org/10.1007/s11030-024-10949-y","journal":{"identity":"molecular-diversity","isVorOnly":false,"title":"Molecular Diversity"},"publishedOn":"2024-08-03 15:57:34","publishedOnDateReadable":"August 3rd, 2024"},"versionCreatedAt":"2024-05-03 09:53:11","video":"","vorDoi":"10.1007/s11030-024-10949-y","vorDoiUrl":"https://doi.org/10.1007/s11030-024-10949-y","workflowStages":[]},"version":"v1","identity":"rs-4334362","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4334362","identity":"rs-4334362","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}