Antimalarial Potential of Synthetic Geraniol and Nerol Analogs

Antimalarial Potential of Synthetic Geraniol and Nerol Analogs | bioRxiv /* */ /* */ <!-- <!-- /*! * yepnope1.5.4 * (c) WTFPL, GPLv2 */ (function(a,b,c){function d(a){return"[object Function]"==o.call(a)}function e(a){return"string"==typeof a}function f(){}function g(a){return!a||"loaded"==a||"complete"==a||"uninitialized"==a}function h(){var a=p.shift();q=1,a?a.t?m(function(){("c"==a.t?B.injectCss:B.injectJs)(a.s,0,a.a,a.x,a.e,1)},0):(a(),h()):q=0}function i(a,c,d,e,f,i,j){function k(b){if(!o&&g(l.readyState)&&(u.r=o=1,!q&&h(),l.onload=l.onreadystatechange=null,b)){"img"!=a&&m(function(){t.removeChild(l)},50);for(var d in y[c])y[c].hasOwnProperty(d)&&y[c][d].onload()}}var j=j||B.errorTimeout,l=b.createElement(a),o=0,r=0,u={t:d,s:c,e:f,a:i,x:j};1===y[c]&&(r=1,y[c]=[]),"object"==a?l.data=c:(l.src=c,l.type=a),l.width=l.height="0",l.onerror=l.onload=l.onreadystatechange=function(){k.call(this,r)},p.splice(e,0,u),"img"!=a&&(r||2===y[c]?(t.insertBefore(l,s?null:n),m(k,j)):y[c].push(l))}function j(a,b,c,d,f){return q=0,b=b||"j",e(a)?i("c"==b?v:u,a,b,this.i++,c,d,f):(p.splice(this.i++,0,a),1==p.length&&h()),this}function k(){var a=B;return a.loader={load:j,i:0},a}var l=b.documentElement,m=a.setTimeout,n=b.getElementsByTagName("script")[0],o={}.toString,p=[],q=0,r="MozAppearance"in l.style,s=r&&!!b.createRange().compareNode,t=s?l:n.parentNode,l=a.opera&&"[object Opera]"==o.call(a.opera),l=!!b.attachEvent&&!l,u=r?"object":l?"script":"img",v=l?"script":u,w=Array.isArray||function(a){return"[object Array]"==o.call(a)},x=[],y={},z={timeout:function(a,b){return b.length&&(a.timeout=b[0]),a}},A,B;B=function(a){function b(a){var a=a.split("!"),b=x.length,c=a.pop(),d=a.length,c={url:c,origUrl:c,prefixes:a},e,f,g;for(f=0;f<d;f++)g=a[f].split("="),(e=z[g.shift()])&&(c=e(c,g));for(f=0;f<b;f++)c=x[f](c);return c}function g(a,e,f,g,h){var i=b(a),j=i.autoCallback;i.url.split(".").pop().split("?").shift(),i.bypass||(e&&(e=d(e)?e:e[a]||e[g]||e[a.split("/").pop().split("?")[0]]),i.instead?i.instead(a,e,f,g,h):(y[i.url]?i.noexec=!0:y[i.url]=1,f.load(i.url,i.forceCSS||!i.forceJS&&"css"==i.url.split(".").pop().split("?").shift()?"c":c,i.noexec,i.attrs,i.timeout),(d(e)||d(j))&&f.load(function(){k(),e&&e(i.origUrl,h,g),j&&j(i.origUrl,h,g),y[i.url]=2})))}function h(a,b){function c(a,c){if(a){if(e(a))c||(j=function(){var a=[].slice.call(arguments);k.apply(this,a),l()}),g(a,j,b,0,h);else if(Object(a)===a)for(n in m=function(){var b=0,c;for(c in a)a.hasOwnProperty(c)&&b++;return b}(),a)a.hasOwnProperty(n)&&(!c&&!--m&&(d(j)?j=function(){var a=[].slice.call(arguments);k.apply(this,a),l()}:j[n]=function(a){return function(){var b=[].slice.call(arguments);a&&a.apply(this,b),l()}}(k[n])),g(a[n],j,b,n,h))}else!c&&l()}var h=!!a.test,i=a.load||a.both,j=a.callback||f,k=j,l=a.complete||f,m,n;c(h?a.yep:a.nope,!!i),i&&c(i)}var i,j,l=this.yepnope.loader;if(e(a))g(a,0,l,0);else if(w(a))for(i=0;i (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];var j=d.createElement(s);var dl=l!='dataLayer'?'&l='+l:'';j.src='//www.googletagmanager.com/gtm.js?id='+i+dl;j.type='text/javascript';j.async=true;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-M677548'); Skip to main content Home About Submit ALERTS / RSS Search for this keyword Advanced Search New Results Antimalarial Potential of Synthetic Geraniol and Nerol Analogs Maurício Mazzine Filho , Isaac Agnelo da Silva Sobreiro , Gabriel dos Santos e Silva , Carlos Alberto de Araújo Silva , Leonardo Vinícius Nogueira Lima , Arthur Vicentini Furtado , João Vitor da Silveira , Marcus Vinícius Nora de Souza , Matheus Felipe Silva Santos , Gabriela Oliveira Castro , Manoel Aparecido Peres , View ORCID Profile Marcell Crispim , Alejandro Miguel Katzin , Mauricio Frota Saraiva , View ORCID Profile Ignasi Bofill Verdaguer doi: https://doi.org/10.1101/2025.08.01.664114 Maurício Mazzine Filho 1 Department of Parasitology, Institute of Biomedical Sciences of the University of São Paulo , São Paulo, Brazil Find this author on Google Scholar Find this author on PubMed Search for this author on this site Isaac Agnelo da Silva Sobreiro 2 LaSIMBio-Laboratory of Synthesis of Bioactive Molecules, Institute of Physics and Chemistry, Federal University of Itajubá , Itajubá, MG, Brazil Find this author on Google Scholar Find this author on PubMed Search for this author on this site Gabriel dos Santos e Silva 2 LaSIMBio-Laboratory of Synthesis of Bioactive Molecules, Institute of Physics and Chemistry, Federal University of Itajubá , Itajubá, MG, Brazil Find this author on Google Scholar Find this author on PubMed Search for this author on this site Carlos Alberto de Araújo Silva 2 LaSIMBio-Laboratory of Synthesis of Bioactive Molecules, Institute of Physics and Chemistry, Federal University of Itajubá , Itajubá, MG, Brazil Find this author on Google Scholar Find this author on PubMed Search for this author on this site Leonardo Vinícius Nogueira Lima 2 LaSIMBio-Laboratory of Synthesis of Bioactive Molecules, Institute of Physics and Chemistry, Federal University of Itajubá , Itajubá, MG, Brazil Find this author on Google Scholar Find this author on PubMed Search for this author on this site Arthur Vicentini Furtado 2 LaSIMBio-Laboratory of Synthesis of Bioactive Molecules, Institute of Physics and Chemistry, Federal University of Itajubá , Itajubá, MG, Brazil Find this author on Google Scholar Find this author on PubMed Search for this author on this site João Vitor da Silveira 2 LaSIMBio-Laboratory of Synthesis of Bioactive Molecules, Institute of Physics and Chemistry, Federal University of Itajubá , Itajubá, MG, Brazil Find this author on Google Scholar Find this author on PubMed Search for this author on this site Marcus Vinícius Nora de Souza 3 Oswaldo Cruz Foundation, Institute of Drug Technology of FarManguinhos , 21041-250, Rio de Janeiro, RJ, Brazil Find this author on Google Scholar Find this author on PubMed Search for this author on this site Matheus Felipe Silva Santos 1 Department of Parasitology, Institute of Biomedical Sciences of the University of São Paulo , São Paulo, Brazil Find this author on Google Scholar Find this author on PubMed Search for this author on this site Gabriela Oliveira Castro 1 Department of Parasitology, Institute of Biomedical Sciences of the University of São Paulo , São Paulo, Brazil Find this author on Google Scholar Find this author on PubMed Search for this author on this site Manoel Aparecido Peres 1 Department of Parasitology, Institute of Biomedical Sciences of the University of São Paulo , São Paulo, Brazil Find this author on Google Scholar Find this author on PubMed Search for this author on this site Marcell Crispim 4 Department of Clinical and Toxicological Analyses, School of Pharmaceutical Sciences, Federal University of Alfenas , Alfenas, MG, Brazil Find this author on Google Scholar Find this author on PubMed Search for this author on this site ORCID record for Marcell Crispim Alejandro Miguel Katzin 1 Department of Parasitology, Institute of Biomedical Sciences of the University of São Paulo , São Paulo, Brazil Find this author on Google Scholar Find this author on PubMed Search for this author on this site For correspondence: amkatzin{at}icb.usp.br Mauricio Frota Saraiva 2 LaSIMBio-Laboratory of Synthesis of Bioactive Molecules, Institute of Physics and Chemistry, Federal University of Itajubá , Itajubá, MG, Brazil Find this author on Google Scholar Find this author on PubMed Search for this author on this site For correspondence: mauriciosaraiva{at}unifei.edu.br Ignasi Bofill Verdaguer 1 Department of Parasitology, Institute of Biomedical Sciences of the University of São Paulo , São Paulo, Brazil Find this author on Google Scholar Find this author on PubMed Search for this author on this site ORCID record for Ignasi Bofill Verdaguer For correspondence: ig_la123{at}hotmail.com Abstract Full Text Info/History Metrics Preview PDF Abstract Drug resistance is a major threat to malaria control, and thus new drugs are required to fight against this parasitosis. To accelerate drug development, it is of special interest the exploration of natural compounds or repositioning drugs already employed for other diseases. Considering this, previous studies have found that diverse plant terpenes arrest Plasmodium parasites in vitro and in vivo models. However, most terpenes possess low toxicity for the parasite and/or face pharmacokinetic issues. Here, we report several new acyclic monoterpene analogs which possess great antiplasmodial activity in vitro (50% inhibitory concentration at low micromolar scale) against P. falciparum parasites. Also, in vitro studies using hepatocellular carcinoma cells (HepG2) demonstrated remarkable selectivity for malaria parasites. Furthermore, bioinformatic approaches revealed that these compounds possess acceptable pharmacological properties. All these results suggest that acyclic monoterpene analogues could serve as a promising starting point for the development of synthetic terpenes as antimalarial drugs. 1 INTRODUCTION Plasmodium falciparum is the causative agent of human malaria. In 2022, the World Health Organization reported an estimated 249 million cases of malaria and 608,000 malaria-related deaths [ 1 ] . Resistance to current antimalarial drugs is arguably the most significant challenge to controlling malaria [ 1 ] . Therefore, the identification and development of novel antimalarial therapies are urgently needed. To accelerate drug development, there is significant interest in exploring natural compounds or their analogues [ 2 , 3 ] . One of the most studied metabolic pathways in the malaria parasite is the isoprenoid biosynthesis via the methylerythritol phosphate (MEP) pathway [ 4 ] . The MEP pathway leads the biosynthesis of farnesyl pyrophosphate (FPP, 15 carbon), and geranylgeranyl pyrophosphate (GGPP, 20 carbon) [ 5 , 6 ] . These metabolites are essential for the farnesylation and geranylgeranylation of proteins, as well as the biosynthesis of ubiquinone or dolichol 7 – 9 ] . Due to their chemical structures being similar to isoprenoid intermediates, our group explored the antiplasmodial activity and metabolic effects of several plant terpenes, including nerolidol, perillyl alcohol, limonene, and linalool [ 10 – 14 ] . Most of these terpenes inhibit the in vitro growth of P. falciparum parasites. In vivo , perillyl alcohol and nerolidol administered via the inhalatory route demonstrated some antimalarial activity in animal models [ 12 , 14 ] . Nerolidol, limonene, and linalool inhibited dolichol biosynthesis and protein prenylation; nerolidol and linalool also inhibited the biosynthesis of the isoprenic side chain of ubiquinones [ 11 ] . However, most of the mentioned terpenes only exhibit toxicity for the parasite at millimolar concentrations (e.g., linalool and limonene), which are unlikely to be achieved in a clinical setting. Furthermore, these compounds have not yet been used in clinical settings for any pathology, probably due to their low bioavailability via preferred administration routes, such as oral administration [ 12 , 14 ] . In the previous work [ 15 ] we described the synthesis and antitrypanosoma activity of GIB24 a geranyl-diamine that showed promising antiparasitic activity. To explore this compound as a potential agent to other parasitic diseases and inspired by the potential of natural terpenes to act in the MEP pathway of P. falciparum we investigated the antiplasmodial activity of GIB24 and fourteen others acyclic monoterpenes, analogous to nerol or geraniol. As demonstrated below, these compounds exhibited promising antiplasmodial activity and interesting selectivity to the parasite. 2 RESULTS AND DISCUSSION 2.1 Chemistry 2.1.1 Preparation of nerol and geraniol analogues 3a-h; 4a-e and 6a-b The synthesis of the proposed analogs was initiated by treating terpene alcohols, nerol ( 1 ) or geraniol ( 2 ), with phosphorus tribromide (PBr 3 ) at negative temperatures in anhydrous tetrahydrofuran (THF). The formation of the respective terpenyl bromides 3 and 4 were monitored using thin-layer chromatography (TLC) and infrared (IR) spectroscopy. In the IR spectra of geraniol and nerol bromides, the band of O-H stretching (approximately 3300 cm⁻¹) was not observed, indicating the occurrence of the reaction. In the TLC a spot with high retention factor (rf) was observed. Subsequently, the bromides reacted with excess of various nucleophiles at room temperature to yield the desired compounds 3a-h , with yields in the range of 20-65% and 4a - e (yields 34-85%). In the IR spectra of geranyl or neryl analogues 3a-d , 3g , 4a - b , and 4d was observed the typical broadband of O- H stretching between 3291-3394 cm⁻¹, indicating the occurrence of the reaction. For the analogues 3e , 3f , and 3h without hydroxyl group, the occurrence of reaction was verified by the presence in the IR spectra of N-H stretching between 3301-3352 cm⁻¹, indicating the occurrence of the reaction. The neryl aminoalcohols 3a and 3b were subjected to mesylation reactions by treatment with methanesulfonyl chloride (MsCl) and triethylamine (Et 3 N) in anhydrous dichloromethane (DCM). The reactions were initiated at low temperature (0°C), and after the addition of the reagents, the system was allowed to warm to room temperature for 12 hours, yielding the mesylated intermediates 5a - b . The formation of compounds 5a - b was monitored using thin-layer chromatography (TLC) and infrared (IR) spectroscopy, and the intermediates were used immediately after their preparation. The final compounds ( 6a - b ) were obtained by reacting to the mesylated intermediates 5a - b with ethanolamine at room temperature. The compounds 6a and 6b were obtained with yields of 45 and 29% respectively. In the IR spectra of neryl analogues 6a and 6b was observed the typical broadband of O- H stretching between 3351-3362 cm⁻¹, indicating the occurrence of the reaction. In the 13 C NMR spectra of these compounds the signal of both, terpene (C=C; 151.5-109.9 ppm) and the aminoalcohol, diamine or thioamine groups (65.2-8.3 ppm) were observed, indicating the final product formation. Moreover, the observed m/z values in mass spectra agree with the calculated values (see supplementary material). The reactions outlined are shown in Figure 1 . Download figure Open in new tab Figure 1: Reagents and conditions: (a) PBr 3 , anhydrous THF, (-18°C for geraniol, 40 min.) or (-35°C for nerol, 90 min); (b and c) methylaminoethanol ( 3a and 4b ), 2-(ethylamino)ethanol ( 3b ), ethanolamine ( 3c ), propanolamine ( 3d ), 2- (ethylthio)ethylamine ( 3e ), 2-(methylthio)ethylamine ( 3f ), 2-(dimethylamino)ethanol ( 3g ), 1,4-diaminobutane ( 3h ), 2-amino-2- methyl-1-propanol ( 4a ), triethylamine ( 4c ), triethanolamine ( 4d ), ethane-1,2-diamine ( 4e ) [ 15 ] , dry DCM, r.t, 24h; (d) MsCl, dry DCM, 0 °C – r.t, 12h; (e) diethanolamine, DMF, r.t, 18h. 2.2 Biological assays 2.2.1 Effects on Plasmodium falciparum growth and HepG2 selectivity The growth of P. falciparum in the presence of various concentrations of acyclic monoterpene analogues was monitored to obtain the dose-response curve and calculate the IC 50 values ( Table 1 ). The results showed that all acyclic monoterpene analogues followed a sigmoid dose-response curve and exhibited diverse IC 50 values. The three most potent compounds were 4e (GIB24) with 8.94 ± 1.31 µM, 3e with 7.49 ± 1.43 µM, and 3f with 3.14 ± 1.18 µM. In contrast, the least potent compounds were 4b with 121.10 ± 20.96 µM, 4a with 133.23 ± 14.25 µM, and 6b with 190.63 ± 33.95 µM. Despite the high IC 50 values for ( 4b , 4a , and 6b ) all synthesized compounds were more active than their respective natural terpene. View this table: View inline View popup Download powerpoint Table 1. In vitro antimalarial and cytotoxic activities of acyclic monoterpene analogs. The figure shows dose-response curves of P. falciparum proliferation and HepG2 cell viability after 48 hours of exposure to acyclic monoterpene analogs. The table presents the IC 50 values (mean ± SD from three independent experiments) for P. falciparum and HepG2 cells. Additionally, the table includes the Selectivity Index (SI) of each compound. * Indicates that the SI values for nerol and geraniol. Values were estimated using the maximum evaluated concentration tested against HepG2: >1000 µM for nerol and >400 µM for geraniol as reported by Polo et al., 2011 [ 16 ] and Silva et al., 2021 [ 17 ] , respectively. View this table: View inline View popup Table 2. ADME-Tox study of geraniol and nerol analogs . The figure presents the ADME-Tox parameters of the compounds analyzed in this study. ADME-Tox analysis predicts compound behavior and toxicity through several parameters. TPSA (Topological Polar Surface Area) indicates cell permeability, where values <140 suggest high permeability, while higher values imply reduced absorption. WLOGP assesses lipophilicity, with values between 1 and 3 indicating an optimal balance for solubility and permeability. GI Absorption evaluates gastrointestinal absorption as high, moderate, or low, with high absorption preferred for oral administration. BBB Permeant determines the ability to cross the blood-brain barrier, with“Yes” suggesting potential central nervous system activity. PGP Substrate identifies substrates of P-glycoprotein, where “Yes” may reduce bioavailability due to cellular efflux. CL-Plasma (Plasma Clearance) measures the rate of compound removal from plasma, with lower values indicating prolonged retention. T1/2 (Half-life) reflects the duration of therapeutic action, with higher values suggesting longer action. AMES evaluates mutagenic potential (positive indicating genotoxicity, negative indicating safety), and Carcinogenicity assesses cancer risk, where values between 0-0.3 indicates low probability of being carcinogenic; values between 0.3-0.7 indicates medium probability of being carcinogenic; and values between 0.7-1.0 indicate high probability of being carcinogenic. These parameters guide the selection of safe and effective drug candidates. Computational modeling was performed using the SwissADME and ADMETlab 3.0 platforms [ 18 ] . Subsequently, the CC 50 values of these compounds were determined in HepG2 cells. The most cytotoxic compounds were 3e with 86.51 ± 29.13µM, 3h with 62.58 ± 28.65 µM and 4e with 34.35 ± 2.30, while the least cytotoxic were 3d with 458.00 ± 205.80 µM, 3a with 604.83 ± 28.88 and 6a with 742.50 ± 230.87 µM. Notably, in this assay, a maximum concentration of 1 mM was tested, and some compounds did not result in a complete loss of viability. For compounds 4b , 3g , 6b , and 4d , it was not possible to calculate the CC 50 value, with GraphPad Prism analysis estimating it to be >500 for the first and >1000 for the other three, respectively. Nonetheless, the Selectivity Index (SI) was calculated either as a defined ratio or as a minimum value when CC 50 values were not obtained. The most selective compounds for the malaria parasite were 4d with >14.25 SI value, 3f with 32.49 SI value and 3g with >43.31 SI value. Conversely, the least selective were 4b with >4.13 SI value, 4e with 3.84 and 4a with 2.92 SI value. As observed, most compounds exhibited an SI > 10, clearly indicating their promising potential as antimalarial agents. These results show the promising potential of the synthesized analogs. All synthesized compounds exhibited antiplasmodial activity and were more active than their respective natural terpene nerol or geraniol. The ( E / Z ) isomerism of the double bond play an important role in the antiplasmodial activity of the monoterpene analogs. The nerol analog ( Z -isomer, compound 3a , IC₅₀ = 48.90 ± 7.15 µM) displayed greater antimalarial activity than the geraniol analog ( E -isomer, compound 4b , IC₅₀ = 121.10 ± 20.96 µM). The carbon elongation chain between the nitrogen (N) and oxygen (O) atoms also improve the antiplasmodial activity. The compound 3d (IC₅₀ = 36.65 ± 5.60 µM) with three carbon atoms spacer displayed greater antiplasmodial activity than the respective analog 3c (IC₅₀ = 49.71 ± 2.70 µM) with two carbon atoms spacer. For the aminoalcohol 3c with the neryl side chain, the insertion of alkyl substituent group on the nitrogen (N) atom, only promote sligth variation on the IC 50 values. These can be observed when the aminoalcohols 3a , N -methyl substituted (IC₅₀ = 48.90 ± 7.15 µM) and 3b , N -ethyl substituted (IC₅₀ = 41.31 ± 3.08 µM) were compared to 3c (IC₅₀ = 49.71 ± 2.70 µM). However, the insertion of an additional methyl group, as in compound 3g (IC₅₀ = 23.09 ± 3.74 µM), provides a significant increase in antiplasmodial activity. This enhanced activity may be associated with the permanent positive formal charge formed on the nitrogen atom. Supporting this hypothesis, other compounds with positive formal charge, such as 4c and 4e (IC₅₀ = 14.06 ± 1.05 and 8.94 ± 1.31 µM, respectively) also exhibited higher activity. The replacement of a hydroxyl group (OH) by a bulky group as (S-Me or S-Et) also improves the antiplasmodial activity. These can be observed when the sulfur compounds 3e (IC₅₀ = 7.49 ± 1.43 µM) and 3f (IC₅₀ = 3.14 ± 1.18 µM) were compared to 3c (IC₅₀ = 49.71 ± 2.70 µM). The selectivity index (SI) is also improved when ethyl group in the sulfur atom (S-Et) was changed by methyl group (S-Me). In general, compounds with a hydroxyl group (terpenyl aminoalcohols) showed low antiplasmodial activity ( 3a - d , 4a - b , 6a - b ). These results suggest that the electronic and steric effects introduced by the exchange of some groups may contribute to improved molecular interactions with the biological target. These findings highlight the importance of atom selection and substitution patterns in modulating the biological efficacy of the synthesized compounds. Figure 2 summarizes some key observations regarding the structure-activity relationship (SAR) of the synthesized derivatives. Download figure Open in new tab Figure 2. Structure-activity relationship for antiplasmodial activity of geraniol and nerol monoterpene analogs. 2.3 ADME-Tox study of acyclic monoterpene analogs An ADME-Tox study evaluates the behavior and toxicity of compounds in the body, a crucial step in drug development [ 18 ] . It includes absorption (how the compound is absorbed and its bioavailability), distribution, metabolism (enzymatic transformations that may generate active or toxic metabolites), and excretion (elimination of the compound). Additionally, it analyzes toxicity to identify potential adverse effects, such as genotoxicity or organ toxicity. As previously discussed, one of the challenges in using terpenes as drugs lies in their unfavorable pharmacokinetic characteristics. Therefore, we deemed it essential to conduct an ADME-Tox study to evaluate the pharmacological viability of the new compounds under study, emphasizing predictions of absorption, distribution, and toxicity. Predictions were performed for TPSA (Topological Polar Surface Area), which measures the polar surface area of a molecule, indicating its ability to form hydrogen bonds. Low TPSA values generally suggest higher cell permeability, while high values indicate lower absorption; WLOGP, a partition coefficient that assesses the lipophilicity of the compound, essential for predicting its solubility in lipids and water, influencing permeability and distribution; The GI Absorption parameter, which indicates the efficiency with which the compound is absorbed in the gastrointestinal tract, categorized as high, moderate, or low; BBB Permeant, a parameter that evaluates whether the compound can cross the blood-brain barrier, a crucial factor for drugs targeting the central nervous system where malaria parasite can be found; the PGP Substrate status, a parameter that checks if the compound is a substrate of P-glycoprotein, an efflux protein that may limit intestinal absorption (Caco-2 permeability) or brain penetration; CL- Plasma (Plasma Clearance) refers to the rate at which the compound is removed from plasma, influencing the duration of its therapeutic action; and the T1/2 (Half-life) time, which represents the time required for the compound’s plasma concentration to be reduced by half, a key parameter for determining dosing frequency. In terms of toxicity, it was decided to evaluate the AMES test, to evaluate the compound’s toxic potential, and Carcinogenicity potential. The ADME-Tox analysis results indicate that the analyzed molecules have low TPSA values, ranging from 0.00 to 60.69, suggesting good cell permeability and absorption potential for most compounds. WLOGP values for the majority are >1, indicating a favorable range of lipophilicity essential for crossing biological membranes and thus accessing parasites. However, two exceptions, 3g and 4d , have negative WLOGP values, which may limit their distribution, as further discussed below. Gastrointestinal absorption also varies, with most compounds exhibiting high absorption, except for 3g and 4c , which show low absorption. Regarding blood-brain barrier permeability, most compounds are permeable, with the exception of 3g and 4c . Four compounds, 3g , 4a , 4c , and 4d , are substrates of P-glycoprotein, which may limit their bioavailability, as this protein is associated with the cellular efflux of drugs. Intestinal permeability values (Caco-2 permeability) range from-4.65 to-5.16, indicating moderate to low permeability. Plasma clearance rates (CL-Plasma) are between 5.87 and 12.63, suggesting that most compounds have moderate elimination rates, while half-life (T1/2) ranges from 0.88 to 1.70, indicating relatively rapid elimination. In mutagenicity tests (AMES), values range from 0.023 to 0.322, with most compounds classified as low mutagenic risk. Regarding carcinogenicity, values range from 0.062 to 0.520, indicating low risk for most compounds, though compounds like 4a show a higher risk. Taking in conclusion, most acyclic monoterpenes have predictions to be drug-like compounds. The exceptions are 3g , 4a , 4c , and 4d , which may present limitations in terms of toxicity and bioavailability. Additionally, the AMDE-Tox study shows that compound 3f exhibits good permeability (TPSA = 37.33), good solubility levels (WLOGP = 3.63), and high gastrointestinal absorption. It also has the ability to cross the blood-brain barrier and is not a substrate of P-glycoprotein. However, it presents low intestinal permeability (Caco-2 permeability =-4.77). Furthermore, it shows good plasma retention (cl-plasma = 11.46) and a moderate half-life (T1/2 = 1.26). The data also indicate low genotoxicity levels (Ames = 0.374) and low carcinogenic potential (Carcinogenicity = 0.154). For these reasons, compound 3f appears to be the best antimalarial candidate presented in this study. 2.4 Discussion Several natural terpenes have been shown to inhibit the in vitro growth of Plasmodium falciparum parasites, highlighting their potential as antimalarial agents. However, a significant limitation of these compounds is their relatively high effecti ve concentrations, often in the millimolar range, which are unlikely to be achievable in clinical settings. Additionally, these terpenes typically suffer from poor bioavailability via preferred administration routes, such as oral administration, further limiting their therapeutic potential [ 12 – 14 ] . For example, geraniol is classified as Generally Recognized As Safe (GRAS) by the U.S. Food and Drug Administration due to its low toxicity, with a lethal dose 50 (LD 50 ) in rats estimated at approximately 3600 mg/kg (oral) [ 19 ] . In fact, mice treated with 120 mg/kg of geraniol for several weeks showed no toxicity signs but an improvement of anti-oxidative defenses [ 20 ] . Regarding its bioavailability, studies in rats have demonstrated that geraniol has an absolute oral absorption rate of 92% in the gut and is capable of crossing the blood-brain barrier, reaching the cerebrospinal fluid [ 20 ] . However, despite its high absorption, geraniol exhibits a short half-life in the bloodstream, calculated to be 12.5 ± 1.5 minutes in rats [ 20 , 21 ] . In terms of antimalarial activity, both geraniol and nerol have shown limited efficacy against Plasmodium parasites, with IC₅₀ values exceeding 100 µM, indicating weak or negligible antiparasitic effects. This suggests that, while these monoterpenes possess favorable toxicologic properties, their potential as standalone antimalarial agents is limited, and structural modifications may be necessary to enhance their potency and bioavailability. In this study, we aimed to address these challenges by exploring the antiplasmodial potential of synthetic acyclic monoterpene analogues. These compounds were designed to retain structural similarities to natural terpenes while incorporating modifications to improve their pharmacological properties, including better predicted ADME and toxicity profiles, as well as higher selectivity indices (SI) when compared to HepG2 cells. Discussions on the structure-activity relationship were conducted, emphasizing the effects of various structural modifications introduced in the synthesized analogs. These modifications played a crucial role in modulating the biological activity of the compounds. The two more active compounds, 3e (IC₅₀ = 7.49 ± 1.43 µM) and 3f (IC₅₀ = 3.14 ± 1.18 µM) were also the most lipophilic 3e (WLOGP = 4.02) and 3f (WLOGP = 3.63) of all evaluated monoterpene analogs. These results suggest the importance of lipophilicity in the drug design of new lead compounds against P. falciparum . Bioinformatic predictions seem to indicate that the new analogues may possess favorable toxicological characteristics, as well as drug-compatible pharmacokinetics and pharmacodynamics. Our findings demonstrate that Acyclic monoterpene analogues exhibit potent antiplasmodial activity in vitro , with significant selectivity against P. falciparum parasites in comparison to HepG2 human hepatocellular carcinoma cells. Future studies should aim to elucidate these alternative pathways to provide a comprehensive understanding of the mode of action of these compounds and further optimize their therapeutic potential. 3 CONCLUSION In this work we report the synthesis, antiplasmodial activity and structure activity relationship of fifteen geraniol and nerol monoterpene analogs. These compounds exhibit potent antiplasmodial activity in vitro against P. falciparum with significant selectivity index. The more potent compound 3f shows (IC 50 = 3.14 ± 1.18 µM) and (SI = 32.49), at least 35 times more potent than the respectively monoterpene nerol. The compounds showed improved pharmacological characteristics. Considering these findings, the results presented here pave the way for the development of terpene-like antimalarial drugs with improved efficacy and selectivity. 4 EXPERIMENTAL 4.1 Biologic assays 4.1.1 Reagents and stock solutions Albumax I, RPMI-1640 and SYBR Green I nucleic acid gel stain were purchased from Thermo Fisher Scientific (Waltham, Massachusetts, EUA). For in vitro use, sterile stock solutions of acyclic monoterpene analogs were prepared at 100 mM in ethanol. All other reagents for biologic assays were purchased from Sigma® (St. Louis, Missouri USA). 4.1.2 P. falciparum in vitro culture and synchronization The P. falciparum 3D7 strain parasites were cultured in vitro following the Trager and Jensen culture method employing RPMI-1640 medium completed with 0.5% Albumax I into 75 cm 2 or 25 cm 2 cell culture flasks at 37 °C [ 22 , 23 ] . The culture medium pH was adjusted to 7.4 and was introduced a gas mixture of 5% CO 2 , 5% O 2 and 90% N 2 purchased from Air Products Brasil LTDA ® (São Paulo, SP, Brazil). Parasites synchronization at ring stages was performed with 5% (w/v) D-sorbitol solution as described previously [ 24 ] . Parasite development was monitored by Giemsa-stained smears microscopy. PCR for mycoplasma and optic microscopy were used to avoid culture contamination [ 25 ] . 4.1.3 Monitoring Plasmodium falciparum growth Culture (100 μl) was incubated in a 96-well cell plate in dark at room temperature after adding 100 μl of SYBR green I 2/10,000 (vol/vol) in lysis buffer (20 mM Tris [pH 7.5], 5 mM EDTA, 0.008% saponin [wt/vol], 0.08% Triton X-100 [vol/vol]) [ 26 ] . Fluorescence was measured using a POLARstar Omega fluorometer (BMG Labtech, Ortenberg, Germany) with the excitation and emission bands centered at 485 and 530 nm, respectively. The fluorescence values of uninfected erythrocytes were subtracted from the values obtained for infected cells. Results were analyzed by GraphPad Prism® software to determine percentage of viability respect controls. The dose-response curve was estimated together with the concentration of drug required to cause a 50% reduction in parasite proliferation (IC 50 value). Results were analyzed by GraphPad Prism software by adjusting data to a dose–response curve to determine the IC 50 value. 4.1.4 HepG2 cell culture The HepG2 cells were grown routinely in 75 or 25 cm 2 flasks in RPMI medium supplemented with 10% FBS and 10 mg/L gentamicin sulfate. The cultures were maintained in a humidified incubator with 5% CO 2 at 37 °C. Cells were manipulated following the passage and trypsinization procedures described elsewhere [ 27 , 28 ] . PCR for mycoplasma and optic microscopy were used to avoid culture contamination [ 29 ] . 4.1.5 Cell viability assays For cell-viability experiments, confluent cultures were washed in Phosphate Buffered Saline (PBS), trypsinized, centrifuged at 300 g, and suspended in culture media. The cells were cultured in 96-well plates at a density of 10.000 cells/well. The next day, the cells were subjected to different concentrations of drugs. Ethanol controls were performed to ensure no effects related to solvents, and its concentration was always ≥1%. After 48 hours, it was added to cells 10 µL PBS containing 10 mg/L MTT and incubated at 37°C. After 4 hours, 100 µL isopropanol 0.04 M HCl was added to each well. The next day, the absorbance at 595 nm wavelength corrected to 690 nm was monitored in a POLARstar Omega fluorometer® (BMG Labtech®, Ortenberg, Germany), and the results were analyzed by GraphPad Prism® software to determine percentage of viability respect controls. In some cases, the dose-response curve was estimated together with the concentration of drug required to cause a 50% reduction in cell viability (CC 50 value). Results were analyzed by GraphPad Prism software by adjusting data to a dose–response curve to determine the CC 50 value. 4.1.6 Selectivity Index The selectivity index (SI) is a ratio that measures the therapeutic window between antiplasmodial activity and cytotoxicity. SI was calculated by dividing the IC 50 value in HepG2 cells by the IC 50 value in Plasmodium parasites. An SI value >10 was considered promising [ 30 ] . 4.1.7 Bioinformatics Computational modeling to estimate the bioavailability, aqueous solubility, blood brain barrier potential, human intestinal absorption, mutagenicity, and toxicity for the compounds was performed using the SwissAdme and ADMETlab 3.0 plataforms [ 18 ] (Last accessed in January 2025). 4.2 Chemistry 4.2.1 Chemicals and general methods All reagents and solvents were reagent grade and were used without prior purification. All reactions were monitored by thin-layer chromatography (TLC, Sigma-Aldrich ® 60). The terpenyl bromides ( 3 and 4 ) and the mesylated intermediates ( 5a - b ) were purified only by liquid-liquid extraction, and the compounds ( 3a - h , 4a - e and 6a - b ) were purified by liquid-liquid extraction followed by flash chromatography on silica gel Sigma-Aldrich ® 60 (230-400 mesh) using CH 2 Cl 2 :CH 3 OH or CH 2 Cl 2 :CH 3 OH:NH 4 OH as eluent. The IR spectra were acquired on a PerkinElmer Spectrum 100 FTIR spectrophotometer with an Attenuated Total Reflectance (ATR) attachment, and only significant bands were recorded. 1 H NMR (300 MHz) and 13 C NMR (75 MHz) spectra of the final compounds ( 3a - h , 4a - e and 6a - b ) were recorded on solutions in CDCl 3 on a Bruker Avance ACX300 (300MHz). The chemical shifts (δ) were reported in parts per million (ppm) with reference to CDCl 3 ( 13 C, 77.00) or residual CHCl 3 ( 1 H, 7.26). The NMR coupling constants ( J ) were recorded in Hertz. Splitting pattern abbreviations are as follows: s = singlet, d = doublet, t = triplet, td = distorted triplet, and m = multiplet. ESI-HRMS mass spectra were carried out on a Bruker MicroTOF spectrometer. The melting points were determined on an Allerbest apparatus. 4.2.2 General procedure for synthesis of neryl and geranyl bromides 3 and 4 Nerol ( 1 ) and geraniol ( 2 ) (( Z )-3,7-dimethylocta-2,6-dien-1-ol and ( E )-3,7-dimethylocta-2,6-dien-1-ol) were used as starting material to prepare the intermediate bromides. The terpenes (10 mmol) were solubilized in THF (10 mL), and a solution of PBr 3 (3.3 mmol) in THF (5 mL) was dropwise added. The reaction mixture was stirred for 40 minutes at-18 °C for geraniol and 90 minutes at-35 °C for nerol. After, the solution was concentrated in vacuo, and the residual oil was solubilized in diethyl ether/hexane (20 mL; 1:1 v/v) and washed sequentially with NaHCO 3 (2 x 10 mL; 5% m/v) and distilled water (2 x 10 mL). The organic phase was dried over anhydrous Na 2 SO 4 , and the solvent was removed under reduced pressure to furnish the terpenyl bromides 3 and 4 . 4.2.3 General procedure for synthesis of the monoterpene derivatives 3a-h and 4a-e The terpenyl bromides (0,5 mmol) were solubilized in dry dichloromethane (5 mL) and dropwise added to the respective excess of different amines (solubilized in 8 mL of dichlorometane) at room temperature: 2-(Methylamino)ethanol (5 mmol for 3a and 4b ), 2-(Ethylamino)ethanol (5 mmol for 3b ), Ethanolamine (10 mmol for 3c ), Propanolamine (10 mmol for 3d ), 2- (Ethylthio)ethylamine (10mmol for 3e ), 2-(Methylthio)ethylamine (10mmol for 3f ), 2-(Dimethylamino)ethanol (1,1 mmol for 3g ), 1,4-diaminobutane (10mmol for 3h ), 2-Amino-2-methyl-1-propanol (10mmol for 4a ), Triethylamine (1,1 mmol for 4c ), and Triethanolamine (1,1 mmol for 4d ). The reactions were maintained under these conditions for 24 hours. After, the solution was washed sequentially with distilled water (2 x 10 mL) to remove excess amine. The organic phase was dried over anhydrous Na 2 SO 4 and the solvent was removed under reduced pressure. The residual oil was purified by flash chromatography on silica gel using CH 2 Cl 2 :CH 3 OH:NH 4 OH as eluent to provide monoterpene analogs ( 3a - h and 4a - e ). Compound 4e was transformed in your respective hydrochloride salt according to the methodology previously described by our research group [ 15 ] . (Z) -2-((3,7-dimethylocta-2,6-dien-1-yl)(methyl)amino)ethanol ( 3a ): A yellow oil (31%). FTIR (ATR, cm -1 ): 3352 (υ, O-H); 1668 (υ, C=C); 1135 (υ, C-O). 1 H NMR (300 MHz, CDCl 3 ): δ 5.26 (t, J = 6.8 Hz, 1H), 5.07 (s, 1H), 3.67 (t, J = 6 Hz, 2H), 3.16 (d, J = 6.8 Hz, 2H), 2.64 (t, J = 6 Hz, 2H), 2.34 (s, 3H), 2.06 (m, 4H), 1.75 (s, 3H), 1.67 (s, 3H), 1.59 (s, 3H). 13 C NMR (75 MHz, CDCl 3 ): δ 140.80 (C), 132.1 (C), 123.7 (CH), 120.0 (CH), 58.1 (CH 2 ), 58.0 (CH 2 ), 54.8 (CH 2 ), 41.3 (CH 3 ), 32.2 (CH 2 ), 26.4 (CH 2 ), 25.7 (CH 3 ), 23.6 (CH 3 ), 17.7 (CH 3 ). ESI-HRMS [M+H] + m/z calculated for C 13 H 26 NO = 212.2009, found = 212.2001. (Z) -2-((3,7-dimethylocta-2,6-dien-1-yl)(ethyl)amino)ethanol ( 3b ): A yellow oil (47%). FTIR (ATR, cm - ¹): 3391 (υ, O-H); 1667 (υ, C=C); 1071 (υ, C-N); 1043 (υ, C-O). 1 H NMR (300 MHz, CDCl 3 ): δ 5.25 (t, J = 6.9 Hz, 1H), 5.07 (m, 1H), 3.63 (t, J = 6.0 Hz, 2H), 3.24 (d, 6.9 Hz, 2H), 2.71 – 2.64 (m, 4H), 2.06 (m, 4H), 1.74 (s, 3H), 1.67 (s, 3H), 1.60 (s, 3H), 1.11 (t, J = 7.2 Hz, 3H). 13 C NMR (75 MHz, CDCl 3 ): δ 140.6 (C), 132.1 (C), 123.7 (CH), 119.9 (CH), 57.9 (CH 2 ), 54.6 (CH 2 ), 50.4 (CH 2 ), 47.5 (CH 2 ), 32.2 (CH 2 ), 26.4 (CH 2 ), 25.7 (CH 3 ), 23.6 (CH 3 ), 17.7 (CH 3 ), 11.4 (CH 3 ). ESI-HRMS [M+H] + m/z calculated for C 14 H 28 NO = 226.2166, found = 226.2166. (Z) -2-((3,7-dimethylocta-2,6-dien-1-yl)amino)ethanol ( 3c ): A yellow oil (26%). FTIR (ATR, cm - ¹): 3304 (υ, O-H + N-H); 1668 (υ, C=C); 1070 (υ, C-N); 1050 (υ, C-O). 1 H NMR (300 MHz, CDCl 3 ): δ 5.28 (t, J = 6.8 Hz, 1H), 5.07 (s, 1H), 3.70 (t, J = 6.0 Hz, 2H), 3.31 (d, J = 6.8 Hz, 2H), 3.17 (s, 1H, O-H), 2.81 (t, J = 6.0 Hz, 2H), 2.06 (m, 4H), 1.73 (s, 3H), 1.67 (s, 3H), 1.59 (s, 3H). 13 C NMR (75 MHz, CDCl 3 ): δ 140.1 (C), 132.2 (C), 123.7 (CH), 121.2 (CH), 60.1 (CH 2 ), 50.1 (CH 2 ), 46.0 (CH 2 ), 32.1 (CH 2 ), 26.5 (CH 2 ), 25.7 (CH 3 ), 23.4 (CH 3 ), 17.7 (CH 3 ). ESI-HRMS [M+H] + m/z calculated for C 12 H 24 NO = 198.1853, found = 198.1857. ( Z )-3-((3,7-dimethylocta-2,6-dien-1-yl)amino)propan-1-ol ( 3d ): A yellow oil (20%). FTIR (ATR, cm - ¹): 3291 (υ, O-H + N-H); 1667 (υ, C=C); 1105 (υ, C-N); 1066 (υ, C-O). 1 H NMR (300 MHz, CDCl 3 ): δ 5.25 (t, J = 6.9 Hz, 1H), 5.07 (s, 1H), 3.80 (t, J = 5.3 Hz, 2H), 3.27 (d, J = 6.9 Hz, 2H), 3.08 (s, 1H, O-H) 2.89 (t, J = 5.7 Hz, 2H), 2.06 (m, 4H), 1.76-1.72 (m, 5H), 1.67 (s, 3H), 1.59 (s, 3H). 13 C NMR (75 MHz, CDCl 3 ): δ 139.9 (C), 132.1 (C), 123.7 (CH), 121.4 (CH), 63.5 (CH 2 ), 48.5 (CH 2 ), 46.4 (CH 2 ), 32.1 (CH 2 ), 30.2 (CH 2 ), 26.5 (CH 2 ), 25.7 (CH 3 ), 23.4 (CH 3 ), 17.7 (CH 3 ). ESI-HRMS [M+H] + m/z calculated for C 13 H 26 NO = 212.2009 found = 212.2007. (Z) - N -(2-(ethylthio)ethyl)-3,7-dimethylocta-2,6-dien-1-amine ( 3e ): A yellow oil (36%). FTIR (ATR, cm - ¹): 3302 (υ, N-H); 1668 (υ, C=C); 1109 (υ, C-N). 1 H NMR (300 MHz, CDCl 3 ): δ 5.32 (t, J = 6.5 Hz, 1H), 5.07 (s, 1H), 3.38 (d, J = 6.5 Hz, 2H), 2.92 – 2.77 (m, 4H), 2.55 (q, J = 7.4 Hz, 2H), 2.06 (m, 4H), 1.74 (s, 3H), 1.67 (s, 3H), 1.59 (s, 3H), 1.25 (t, J = 7.4 Hz, 3H). 13 C NMR (75 MHz, CDCl 3 ) δ 141.1 (C), 132.2 (C), 123.6 (CH), 120.0 (CH), 47.0 (CH 2 ), 45.7 (CH 2 ), 32.2 (CH 2 ), 30.0 (CH 2 ), 26.5 (CH 2 ), 25.9 (CH 2 ), 25.7 (CH 3 ), 23.5 (CH 3 ), 17.7 (CH 3 ), 14.8 (CH 3 ). ESI-HRMS [M+H] + m/z calculated for C 14 H 28 NS = 242.1937 found = 242.1931. (Z) -3,7-dimethyl- N -(2-(methylthio)ethyl)octa-2,6-dien-1-amine ( 3f ): A yellow oil (37%). FTIR (ATR, cm - ¹): 3301 (υ, N-H); 1668 (υ, C=C); 1108 (υ, C-N). 1 H NMR (300 MHz, CDCl 3 ): δ 5.34 (t, J = 6.8 Hz, 1H), 5.07 (s, 1H), 3.42 (d, J = 6.8 Hz, 2H), 2.93 (t, J = 6.8 Hz, 2H), 2.79 (t, J = 6.8 Hz, 2H), 2.11 (s, 3H), 2.07 (m, 4H), 1.75 (s, 3H), 1.68 (s, 3H), 1.59 (s, 3H). 13 C NMR (75 MHz, CDCl 3 ): δ 141.8 (C), 132.3 (C), 123.5 (CH), 119.2 (CH), 46.2 (CH 2 ), 45.6 (CH 2 ), 32.2 (CH 2 ), 32.1 (CH 2 ), 26.4 (CH 2 ), 25.7 (CH 3 ), 23.4 (CH 3 ), 17.7 (CH 3 ), 15.3 (CH 3 ). ESI-HRMS [M+H] + m/z calculated for C 13 H 26 NS = 228.1781 found = 228.1774. ( Z )- N -(2-hydroxyethyl)- N,N ,3,7-tetramethylocta-2,6-dien-1-aminium bromide ( 3g ): A pale-yellow solid (65%). mp (°C): 155-160. FTIR (ATR, cm - ¹): 3361 (υ, N-H); 1660 (υ, C=C); 1085 (υ, C-O), 1036 (υ, C-N). 1 H NMR (300 MHz, CDCl 3 ) δ 5.39 (t, J = 7.9 Hz, 1H), 5.05 (t, J = 6.9 Hz, 1H), 4.11-4.08 (m, 4H), 3.68 (td, 2H), 3.26 (s, 6H), 2.19 – 2.08 (m, 4H), 1.86 (s, 3H), 1.65 (s, 3H), 1.57 (s, 3H). 13 C NMR (75 MHz, CDCl 3 ): δ 151.5 (C), 132.9 (C), 122.8 (CH), 111.3 (CH), 65.2 (CH 2 ), 63.2 (CH 2 ), 56.0 (CH 2 ), 50.9 (CH 3 x2), 32.4, 26.1 (CH 2 ), 25.7 (CH 3 ), 24.0 (CH 3 ), 17.8 (CH 3 ). ESI-HRMS [M] + m/z calculated for C 14 H 28 NO = 226.2166 found = 226.2169. (Z)-N 1 -(3,7-dimethylocta-2,6-dien-1-yl)butane-1,4-diamine ( 3h ): A yellow oil (37%). FTIR (ATR, cm - ¹): 3352 (υ as , N-H); 3285 (υ s , N-H); 1668 (υ, C=C); 1587 (d, NH 2 ) 1108 (υ, C-N). 1 H NMR (300 MHz, CDCl 3 ): δ 5.26 (t, J = 6.7 Hz, 1H), 5.07 (s, 1H), 5.71 (s, 1H, N-H), 3.25 (d, J = 6.8 Hz, 2H), 2.75 (t, J = 6 Hz, 2H), 2.64 (d, J = 6.3 Hz, 2H), 2.04 (m, 4H), 1.71 (s, 3H), 1.66 (s, 3H), 1.57 (s, 7H). 13 C NMR (75 MHz, CDCl 3 ): δ 139.2 (C), 132.0 (C), 123.8 (CH), 122.0 (CH), 48.6 (CH 2 ), 46.5 (CH 2 ), 41.4 (CH 2 ), 32.1 (CH 2 ), 30.3 (CH 2 ), 26.9 (CH 2 ), 26.5 (CH 2 ), 25.8 (CH 3 ), 23.4 (CH 3 ), 17.7 (CH 3 ). ESI-HRMS [M+H] + m/z calculated for C 14 H 29 N 2 = 225.2326 found = 225.2334. (E )-2-((3,7-dimethylocta-2,6-dien-1-yl)amino)-2-methylpropan-1-ol ( 4a ): A yellow oil (34%). FTIR (ATR, cm - ¹): 3407 (υ, O-H + N-H); 1667 (υ, C=C); 1164 (υ, C-N); 1052 (υ, C-O). 1 H NMR (300 MHz, CDCl 3 ): δ 5.22 (td, 1H), 5.10 (td, 1H), 3.30 (s, 2H), 3.12 (d, J = 6.8 Hz, 2H), 2.17 – 1.97 (m, 4H), 1.67 (s, 3H), 1.63 (s, 3H), 1.59 (s, 3H), 1.08 (s, 6H). 13 C NMR (75 MHz, CDCl 3 ): δ 137.8 (C), 131.6 (C), 124.1 (CH), 122.8 (CH), 68.4 (CH 2 ), 53.7 (C), 39.6 (CH 2 ), 39.5 (CH 2 ), 26.5 (CH 2 ), 25.7 (CH 3 ), 24.0 (2xCH 3 ), 17.7 (CH 3 ), 16.2 (CH 3 ), 17.7 (CH 3 ). (E )-((3,7-dimethylocta-2,6-dien-1-yl)(methyl)amino)ethanol ( 4b ): A yellow oil (71%). FTIR (ATR, cm - ¹): 3355 (υ, O-H); 1667 (υ, C=C); 1073 (υ, C-N); 1030 (υ, C-O). 1 H NMR (300 MHz, CDCl 3 ): δ 5.29 (td, 1H), 5.06 (td, 1H), 3.74 (t, J = 5.3 Hz, 2H), 3.28 (d, J = 7.1 Hz, 2H), 2.89 (s, 1H), 2.74 (t, J = 5.3 Hz, 2H), 2.43 (s, 3H), 2.18 – 2.05 (m, 4H), 1.67 (s, 6H), 1.60 (s, 3H). 13 C NMR (75 MHz, CDCl 3 ): δ 142.4 (C), 131.9 (C), 123.7 (CH), 117.7 (CH), 58.1 (CH 2 ), 57.7 (CH 2 ), 54.8 (CH 2 ), 41.1 (CH 3 ), 39.8 (CH 2 ), 26.3 (CH 2 ) 25.7 (CH 3 ), 17.7 (CH 3 ), 16.5 (CH 3 ). (E)-N,N,N- triethyl-3,7-dimethylocta-2,6-dien-1-aminium bromide ( 4c ): A brown light solid (54%). mp (°C): 86-88. FTIR (ATR, cm - ¹): 1663 (υ, C=C); 1011 (υ, C-N). 1 H NMR (300 MHz, CDCl 3 ): δ 5.18 (t, J = 7.8 Hz, 1H), 4.99 (s, 1H), 4.04 (d, J = 7.8 Hz, 2H), 3.43 (q, J = 7.3 Hz, 6H), 2.14-2.13 (m, 4H), 1.82 (s, 3H), 1.66 (s, 3H), 1.59 (s, 3H), 1.40 (t, J = 7.3 Hz, 9H). 13 C NMR (75 MHz, CDCl 3 ): δ 151.0 (C), 132.6 (C), 123.1 (CH), 109.9 (CH), 56.1 (CH 2 ), 53.0 (2xCH 2 ), 40.1 (CH 2 ), 26.0 (CH 3 ), 25.8 (CH 3 ), 17.8 (CH 3 ), 17.5 (CH 3 ), 8.3 (CH 3 ). (E)-N,N,N- tris(2-hydroxyethyl)-3,7-dimethylocta-2,6-dien-1-aminium bromide ( 4d ): A white solid (85%). mp (°C): 95-97. FTIR (ATR, cm - ¹): 3393, 3334 and 3204 (υ, O-H); 1657 (υ, C=C); 1100 (υ, C-N), 1045 (υ, C-O). 1 H NMR (300 MHz, CDCl 3 ): δ 5.38 (td, 1H), 5.02 (t, J = 7.0 Hz, 1H), 4.77 (s, 3H), 4.24 (d, J = 7.4 Hz, 2H), 3.70 (sl, 6H), 2.14 (sl, 4H), 1.79 (s, 3H), 1.67 (s, 3H), 1.57 (s, 3H). 13 C NMR (75 MHz, CDCl 3 ): δ 150.7 (C), 132.4 (C), 123.3 (CH), 110.9 (CH), 61.4 (3xCH 2 ), 59.7 (CH 2 ), 55.8 (3xCH 2 ), 40.2 (CH 2 ), 26.2 (CH 2 ), 17.9 (CH 3 ), 17.5 (CH 3 ), 8.3 (3xCH 3 ). ESI-HRMS [M+H] + m/z calculated for C 16 H 32 NO 3 = 286.2377 found = 286.2373. 4.2.4 General procedure for synthesis of mesylated intermediates 5a-b In a 25 mL flask, 1 mmol of the derivatives 3a and 3b was dissolved in 1 mL of dichloromethane (DCM), previously dried over molecular sieves. To this solution, a stoichiometric amount of 1.5 mmol of methanesulfonyl chloride (MsCl) was added per mmol of products 3a and 3b . The reaction mixture was then cooled in an ice bath (0°C), and a solution of 2 mmol of triethylamine in 1 mL of DCM was added dropwise over 30 minutes with constant stirring. The temperature was maintained only during the triethylamine addition, after which the system was allowed to gradually warm to room temperature. The reaction mixture was then left under these conditions for 12 hours. The intermediate compounds 5a and 5b were used immediately without purification. The formation of mesylated products was confirmed by thin-layer chromatography (TLC) and infrared (IR) spectroscopy. 4.2.5 General procedure for synthesis of the nerol derivatives 6a-b In a 25 mL flask, 1 mmol of the derivatives 5a and 5b were dissolved in 1 mL of dimethylformamide (DMF). To this solution, a stoichiometric amount of 1.5 mmol of diethanolamine (solubilized in 2mL of DMF) was added. The reaction mixture kept stirring at room temperature for 18 hours. After, the solution was washed sequentially with distilled water (2 x 10 mL) to remove excess amine. The organic phase was dried over anhydrous Na 2 SO 4 and the solvent was removed under reduced pressure. The residual oil was purified by flash chromatography on silica gel using CH 2 Cl 2 :CH 3 OH:NH 4 OH as eluent to provide neryl aminoalcohols 6a and 6b . (Z) -2,2’-((2-((3,7-dimethylocta-2,6-dien-1-yl)(ethyl)amino)ethyl)azanediyl)diethanol ( 6a ): A yellow oil (29%). FTIR (ATR, cm -1 ): 3362 (υ, O-H); 1667 (υ, C=C); 1068 (υ, C-N); 1139 (υ, C-O). 1 H NMR (300 MHz, CDCl 3 ): δ 5.26 (t, J = 6.7 Hz, 1H), 5.07 (s, 1H), 3.57 (t, J = 6.0 Hz, 2H), 3.16 (d, J = 6.7 Hz, 2H), 2.69 – 2.52 (m, 10H), 2.04 (m, 4H), 1.74 (s, 3H), 1.66 (s, 3H), 1.59 (s, 3H), 1.08 (t, J = 7.1 Hz, 3H). 13 C NMR (75 MHz, CDCl 3 ) δ 140.2 (C), 132.0 (C), 123.8 (CH), 119.8 (CH), 59.9 (CH 2 ), 57.6 (CH 2 ), 52.4 (CH 2 ), 51.7 (CH 2 ), 50.0 (CH 2 ), 47.1 (CH 2 ), 32.2 (CH 2 ), 26.5 (CH 2 ), 25.8 (CH 3 ), 23.6 (CH 3 ), 17.7 (CH 3 ), 10.7 (CH 3 ). ESI-HRMS [M+H] + m/z calculated for C 18 H 37 N 2 O 2 = 313.2850, found = 313.2853. (Z)- 2,2’-((2-((3,7-dimethylocta-2,6-dien-1-yl)(methyl)amino)ethyl)azanediyl)diethanol ( 6b ): A yellow oil (45%). FTIR (ATR, cm -1 ): 3351 (υ, O-H); 1667 (υ, C=C); 1135 (υ, C-O). 1 H NMR (300 MHz, CDCl 3 ): δ 5.27 (t, J = 7.0 Hz, 1H), 5.06 (s, 1H), 3.59 (t, J = 6.0 Hz, 4H), 3.22 (d, J = 7.0 Hz, 2H), 2.69 – 2.59 (m, 8H), 2.35 (s, 3H), 2.06 (m, 4H), 1.76 (s, 3H), 1.66 (s, 3H), 1.59 (s, 3H). 13 C NMR (75 MHz, CDCl 3 ) δ 142.0 (C), 132.2 (C), 123.6 (CH), 118.5 (CH), 60.0 (CH 2 x2), 58.1 (CH 2 x2), 55.1 (CH 2 ), 54.4 (CH 2 ), 51.4 (CH 2 ), 40.9 (CH 3 ), 32.1 (CH 2 ), 26.4 (CH 2 ), 25.7 (CH 3 ), 23.6 (CH 3 ), 17.7 (CH 3 ). ESI-HRMS [M+H] + m/z calculated for C 17 H 35 N 2 O 2 = 299.2694, found = 299.2695. AUTHOR CONTRIBUTIONS MMF, MC, GOC, MAP, MFSS, GSS, and IBV contributed to conceptualization, formal analysis, investigation, methodology and writing. IASS, CAAS, LVNL, AVF, JVS and MVNS contributed to the synthesis and characterization of described compounds. IBV, MFS and AMK also contributed in project administration, funding acquisition, supervision and writing – review & editing. FUNDING MFSS is fellow of the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES). IBV and MMF are fellows from the Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); MMF FAPESP process number: 2023/12343-1; IBV FAPESP process number: 2019/13419-6). LVNL is fellow of Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). GSS and CAAS are fellows from the Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG). This work was also supported funding from CAPES, FAPESP (2024/09997-2) (AMK), FAPEMIG (APQ-01455-22) (MFS) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). The authors acknowledge the LRMN-UNIFAL (Federal University of Alfenas) for nuclear magnetic resonance analysis and the RELAM-UNIFEI (APQ-002290-23) CONFLICT OF INTEREST The authors declare no conflicts of interest. Entry for the Table of Contents Download figure Open in new tab In this work, we synthesized and evaluated the antiplasmodial activity of fifteen analogues of the natural monoterpenes geraniol or nerol. The evaluated compounds exhibited strong inhibitory activity, high selectivity index (SI), and promising pharmacological properties based on bioinformatic analyses. Compound 3f emerged as the most potent, being at least 35 times more active than nerol, with remarkable pharmacological predictions. The findings presented here highlight the potential of these compounds as starting points for new antimalarial drugs. Supplementary material Compound 3a Download figure Open in new tab Figure 1. IR spectra of compound 3a . Download figure Open in new tab Figure 2. ¹H NMR spectra of compound 3a in CDCl 3 , 300 MHz. Download figure Open in new tab Figure 3. ¹³C NMR spectra of compound 3a in CDCl 3 , 75 MHz. Download figure Open in new tab Figure 4. High Resolution Mass spectra of compound 4a . Compound 3b Download figure Open in new tab Figure 5. IR spectra of compound 3b . Download figure Open in new tab Figure 6. ¹H NMR spectra of compound 3b in CDCl 3 , 300 MHz. Download figure Open in new tab Figure 7. ¹³C NMR spectra of compound 3b in CDCl 3 , 75 MHz. Download figure Open in new tab Figure 8. High Resolution Mass spectra of compound 3b . Compound 3c Download figure Open in new tab Figure 9. IR spectra of compound 3c . Download figure Open in new tab Figure 10. ¹H NMR spectra of compound 3c in CDCl 3 , 300 MHz. Download figure Open in new tab Figure 11. ¹³C NMR spectra of compound 3c in CDCl 3 , 75 MHz. Download figure Open in new tab Figure 12. High Resolution Mass spectra of compound 3c . Compound 3d Download figure Open in new tab Figure 13. IR spectra of compound 3d . Download figure Open in new tab Figure 14. ¹H NMR spectra of compound 3d in CDCl 3 , 300 MHz. Download figure Open in new tab Figure 15. ¹³C NMR spectra of compound 3d in CDCl3, 75 MHz. Download figure Open in new tab Figure 16. High Resolution Mass spectra of compound 3d . Compound 3e Download figure Open in new tab Figure 17. IR spectra of compound 3e . Download figure Open in new tab Figure 18. ¹H NMR spectra of compound 3e in CDCl 3 , 300 MHz. Download figure Open in new tab Figure 19. ¹³C NMR spectra of compound 3e in CDCl 3 , 75 MHz. Download figure Open in new tab Figure 20. High Resolution Mass spectra of compound 3e . Compound 3f Download figure Open in new tab Figure 21. IR spectra of compound 3f . Download figure Open in new tab Figure 22. ¹H NMR spectra of compound 3f in CDCl3, 300 MHz. Download figure Open in new tab Figure 23. ¹³C NMR spectra of compound 3f in CDCl3, 75 MHz. Download figure Open in new tab Figure 24. High Resolution Mass spectra of compound 3f . Compound 3g Download figure Open in new tab Figure 25. IR spectra of compound 3g . Download figure Open in new tab Figure 26. ¹H NMR spectra of compound 3g in CDCl 3 , 300 MHz. Download figure Open in new tab Figure 27. ¹³C NMR spectra of compound 3g in CDCl 3 , 300 MHz. Download figure Open in new tab Figure 28. High Resolution Mass spectra of compound 3g . Compound 3h Download figure Open in new tab Figure 29. IR spectra of compound 3h . Download figure Open in new tab Figure 30. ¹H NMR spectra of compound 3h in CDCl 3 , 300 MHz. Download figure Open in new tab Figure 31. ¹³C NMR spectra of compound 3h in CDCl 3 , 75 MHz. Download figure Open in new tab Figure 32. High Resolution Mass spectra of compound 3g . Compound 5a Download figure Open in new tab Figure 33. IR spectra of compound 5a . Download figure Open in new tab Figure 34. ¹H NMR spectra of compound 5a in CDCl3, 300 MHz. Download figure Open in new tab Figure 35. ¹³C NMR spectra of compound 5a in CDCl3, 75 MHz. Download figure Open in new tab Figure 36. High Resolution Mass spectra of compound 5a . Compound 5b Download figure Open in new tab Figure 37. IR spectra of compound 5b . Download figure Open in new tab Figure 38. ¹H NMR spectra of compound 5b in CDCl3, 300 MHz. Download figure Open in new tab Figure 39. ¹³C NMR spectra of compound 5b in CDCl3, 75 MHz. Download figure Open in new tab Figure 40. High Resolution Mass spectra of compound 5b . ACKNOWLEDGEMENTS We thank the Blood Center of Sírio Libanês Hospital (São Paulo, Brazil), for the gift of erythrocytes. Funder Information Declared FAPESP REFERENCES [1]. ↵ World Health Organization, World Malaria Rep. 2023 . [2]. ↵ H. Ginsburg , E. Deharo , Malar . J. 2011 , 10, 1. [3]. ↵ T. Nain , S. Sharma , N. Chawariya , J. P. Yadav , Bull. Pharm . Sci. Assiut Univ . 2022 , 45 , 629 . OpenUrl [4]. ↵ I. B. Verdaguer , C. A. Zafra , M. Crispim , R. A. Sussmann , E. A. Kimura , A. M. Katzin , Molecules 2019 , 24 , 3721. DOI: 10.3390/molecules24203721 OpenUrl CrossRef PubMed [5]. ↵ M. B. Cassera , F. C. Gozzo , F. L. D’Alexandri , E. F. Merino , H. A. del Portillo , V. J. Peres , et al. , J. Biol. Chem . 2004 , 279 , 51749 . DOI: 10.1074/jbc.M406360200 OpenUrl Abstract / FREE Full Text [6]. ↵ F. M. Jordão , E. A. Kimura , A. M. Katzin , Mem. Inst. Oswaldo Cruz 2011 , 106 , 134 . DOI: 10.1590/S0074-02762011000900019 OpenUrl CrossRef [7]. ↵ I. B. Verdaguer , M. Crispim , C. A. Zafra , R. A. C. Sussmann , N. L. Buriticá , H. R. Melo , et al. , Antimicrob. Agents Chemother . 2021 , 65 , e01516. DOI: 10.1128/AAC.01516-20 OpenUrl Abstract / FREE Full Text [8]. F. M. Zimbres , A. L. Valenciano , E. F. Merino , A. Florentin , N. R. Holderman , G. He , et al. , Sci. Rep . 2020 , 10 , 1 . DOI: 10.1038/s41598-020-70683-8 OpenUrl CrossRef [9]. ↵ M. Okada , K. Rajaram , R. P. Swift , A. Mixon , J. A. Maschek , S. T. Prigge , P. A. Sigala , eLife 2022 , 11 , e73208. DOI: 10.7554/eLife.73208 OpenUrl CrossRef PubMed [10]. ↵ I. C. Moura , G. Wunderlich , M. L. Uhrig , A. S. Couto , V. J. Peres , A. M. Katzin , E. A. Kimura , Antimicrob. Agents Chemother . 2001 , 45 , 2553. DOI: 10.1128/AAC.45.9.2553-2558.2001 OpenUrl Abstract / FREE Full Text [11]. ↵ H. R. Goulart , E. A. Kimura , V. J. Peres , A. S. Couto , F. A. A. Duarte , A. M. Katzin , Antimicrob. Agents Chemother . 2004 , 48 , 2502. DOI: 10.1128/AAC.48.7.2502-2509.2004 OpenUrl Abstract / FREE Full Text [12]. ↵ A. Y. Saito , A. A. M. Rodriguez , D. S. M. Vega , R. A. Sussmann , E. A. Kimura , A. M. Katzin , Int. J. Antimicrob. Agents 2016 , 48 , 641 . DOI: 10.1016/j.ijantimicag.2016.08.020 OpenUrl CrossRef PubMed [13]. H. B. Gabriel , R. A. Sussmann , E. A. Kimura , A. A. M. Rodriguez , I. B. Verdaguer , G. C. F. Leite , A. M. Katzin , Terpenes Terpenoids 2018 , 1 , 39 . [14]. ↵ A. A. M. Rodriguez , L. J. Carvalho , E. A. Kimura , A. M. Katzin , Int. J. Antimicrob. Agents 2018 , 51 , 370 . DOI: 10.1016/j.ijantimicag.2017.11.016 OpenUrl CrossRef PubMed [15]. ↵ C. M. Azeredo , M. F. Saraiva , M. R. de Oliveira , G. Barbosa , M. V. de Almeida , M. V. N. de Souza , M. J. Soares , Chem. Biol. Interact . 2020 , 330 , 109165 . DOI: 10.1016/j.cbi.2020.109165 OpenUrl CrossRef [16]. ↵ M. P. Polo , R. Crespo , M. G. De Bravo , Cell Biochem . Funct . 2011 , 29 , 452 . DOI: 10.1002/cbf.1776 OpenUrl CrossRef [17]. ↵ B. O. Silva , J. B. Orlando , C. L. Pires , C. A. Hiruma-Lima , I. de M . Gaivao , F. F. Perazzo , E. L. Maistro , J. Toxicol. Environ. Health A 2021 , 84 , 518 . DOI: 10.1080/15287394.2021.1921406 OpenUrl CrossRef [18]. ↵ B. Bakchi , A. D. Krishna , E. Sreecharan , V. B. J. Ganesh , M. Niharika , S. Maharshi , A. B. Shaik , J. Mol . Struct . 2022 , 1259, 132712 . DOI: 10.1016/j.molstruc.2022.132712 OpenUrl CrossRef [19]. ↵ R. J. Lewis Sr., Sax’s Dangerous Properties of Industrial Materials , 11th ed., Wiley-Interscience , 2004 , p. 1449 . [20]. ↵ B. Pavan , A. Dalpiaz , L. Marani , S. Beggiato , L. Ferraro , D. Canistro , et al. , Front. Pharmacol . 2018 , 9 , 18 . DOI: 10.3389/fphar.2018.00018 OpenUrl CrossRef [21]. ↵ W. Mączka , K. Wińska , M. Grabarczyk , Molecules 2020 , 25 , 3303. DOI: 10.3390/molecules25143303 OpenUrl CrossRef [22]. ↵ W. Trager , J. B. Jensen , Science 1976 , 193 , 673 . DOI: 10.1126/science.781840 OpenUrl Abstract / FREE Full Text [23]. ↵ A. Radfar , D. Méndez , C. Moneriz , M. Linares , P. Marín-García , A. Puyet , et al. , Nat. Protoc . 2009 , 4 , 1899. DOI: 10.1038/nprot.2009.218 OpenUrl CrossRef [24]. ↵ C. Lambros , J. P. Vanderberg , J. Parasitol . 1979 , 65 , 418 . [25]. ↵ J. A. Rowe , I. G. Scragg , D. Kwiatkowski , D. J. Ferguson , D. J. Carucci , C. I. Newbold , Mol. Biochem. Parasitol . 1998 , 92 , 177 . DOI: 10.1016/S0166-6851(97)00235-3 OpenUrl CrossRef [26]. ↵ M. Smilkstein , N. Sriwilaijaroen , J. X. Kelly , P. Wilairat , M. Riscoe , Antimicrob. Agents Chemother . 2004 , 48 , 1803. DOI: 10.1128/AAC.48.5.1803-1806.2004 OpenUrl Abstract / FREE Full Text [27]. ↵ P. Kumar , A. Nagarajan , P. D. Uchil , Cold Spring Harb. Protoc . 2018 , 2018 ( 6 ), pdb.prot095505. DOI: 10.1101/pdb.prot095505 OpenUrl Abstract / FREE Full Text [28]. ↵ L. A. Selenius , M. W. Lundgren , R. Jawad , O. Danielsson , M. Björnstedt , Antioxidants 2019 , 8 , 130 . DOI: 10.3390/antiox8050130 OpenUrl CrossRef PubMed [29]. ↵ L. Nikfarjam , P. Farzaneh , Cell J . 2012 , 13 , 203 . [30]. ↵ T. Mokgethi-Morule , D. D. David , Eur. J. Pharm. Sci . 2016 , 84 , 26 . DOI: 10.1016/j.ejps.2016.01.010 OpenUrl CrossRef View the discussion thread. Back to top Previous Next Posted August 01, 2025. Download PDF Email Thank you for your interest in spreading the word about bioRxiv. NOTE: Your email address is requested solely to identify you as the sender of this article. Your Email * Your Name * Send To * Enter multiple addresses on separate lines or separate them with commas. 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Share Antimalarial Potential of Synthetic Geraniol and Nerol Analogs Maurício Mazzine Filho , Isaac Agnelo da Silva Sobreiro , Gabriel dos Santos e Silva , Carlos Alberto de Araújo Silva , Leonardo Vinícius Nogueira Lima , Arthur Vicentini Furtado , João Vitor da Silveira , Marcus Vinícius Nora de Souza , Matheus Felipe Silva Santos , Gabriela Oliveira Castro , Manoel Aparecido Peres , Marcell Crispim , Alejandro Miguel Katzin , Mauricio Frota Saraiva , Ignasi Bofill Verdaguer bioRxiv 2025.08.01.664114; doi: https://doi.org/10.1101/2025.08.01.664114 Share This Article: Copy Citation Tools Antimalarial Potential of Synthetic Geraniol and Nerol Analogs Maurício Mazzine Filho , Isaac Agnelo da Silva Sobreiro , Gabriel dos Santos e Silva , Carlos Alberto de Araújo Silva , Leonardo Vinícius Nogueira Lima , Arthur Vicentini Furtado , João Vitor da Silveira , Marcus Vinícius Nora de Souza , Matheus Felipe Silva Santos , Gabriela Oliveira Castro , Manoel Aparecido Peres , Marcell Crispim , Alejandro Miguel Katzin , Mauricio Frota Saraiva , Ignasi Bofill Verdaguer bioRxiv 2025.08.01.664114; doi: https://doi.org/10.1101/2025.08.01.664114 Citation Manager Formats BibTeX Bookends EasyBib EndNote (tagged) EndNote 8 (xml) Medlars Mendeley Papers RefWorks Tagged Ref Manager RIS Zotero Tweet Widget Facebook Like Google Plus One Subject Area Microbiology Subject Areas All Articles Animal Behavior and Cognition (7635) Biochemistry (17690) Bioengineering (13892) Bioinformatics (41936) Biophysics (21451) Cancer Biology (18588) Cell Biology (25499) Clinical Trials (138) Developmental Biology (13378) Ecology (19899) Epidemiology (2067) Evolutionary Biology (24320) Genetics (15609) Genomics (22506) Immunology (17736) Microbiology (40394) Molecular Biology (17181) Neuroscience (88603) Paleontology (666) Pathology (2832) Pharmacology and Toxicology (4824) Physiology (7641) Plant Biology (15152) Scientific Communication and Education (2045) Synthetic Biology (4294) Systems Biology (9825) Zoology (2271)