Computational Study: Antioxidant Activity of Aspulvinone E Toward Hydroperoxyl and Hydroxyl Radicals

Computational Study: Antioxidant Activity of Aspulvinone E Toward Hydroperoxyl and Hydroxyl Radicals | 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 Computational Study: Antioxidant Activity of Aspulvinone E Toward Hydroperoxyl and Hydroxyl Radicals Belma Gjergjizi Nallbani, Isa Degirmenci This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7678529/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 28 Feb, 2026 Read the published version in Structural Chemistry → Version 1 posted 11 You are reading this latest preprint version Abstract In this study, the antioxidant mechanisms of aspulvinone E were systematically examined via quantum chemical calculations. Thermodynamic and kinetic analyses identified the H-3 hydroxyl group as the most reactive site for hydrogen atom transfer (HAT), exhibiting the lowest Gibbs free energy values for abstraction by •OOH and •OH radicals. Radical adduct formation (RAF) studies confirmed site-specific reactivity, favoring C1 addition by •OOH and C3 addition by •OH. Electronic properties—including moderate ionization potential, high electron affinity, and favorable softness and electrophilicity parameters—position the molecule as a responsive electron donor. HOMO distribution localized over phenyl and furanone moieties highlights targeted radical scavenging enhanced by hydroxyl functionalization. Overall, the combined thermodynamic, kinetic, and electronic profiles suggest that aspulvinone E possesses site-specific reactivity and enhanced stability, making it a promising candidate for antioxidant applications and further biological evaluation. butenolide aspulvinone E antioxidant activity theoretical calculations M06-2X Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Introduction Antioxidants are either naturally occurring [ 1 ] or synthetically produced [ 2 ] substances that prevent the process of oxidation, which generates free radicals. These free radicals have the potential to inflict cellular damage. They are linked to the progression of aging as well as several pathologies, including cancer, cardiovascular disorders, and Alzheimer's disease [ 3 ]. Essentially, antioxidants function as a protective mechanism, neutralizing free radicals and thus safeguarding cellular integrity. Polyphenols are widely recognized for their antioxidant properties [ 4 ]. According to further reports, depending on their chemical structures, the polyphenols affect how quickly they are absorbed and circulated in the blood plasma [ 5 ]. Moreover, the antioxidant activity of polyphenols is influenced by the abundance and location of -OH groups attached to the aromatic ring[ 6 ]. Therefore, emphasizing the molecular structure's influence on the compounds' antioxidant efficacy is extremely important. In recent years, considerable interest has been shown in discovering alternative natural and safe sources of antioxidants for food applications, with a particular emphasis on those derived from plants. For example, fungi have also been acknowledged as an abundant source of novel bioactive compounds[ 7 ]. Aspergillus terreus is a common fungus extensively used in the chemical and pharmaceutical industries [ 8 ]. Aspergillus species are a common source of butenolides, also termed butyrolactones, that exhibit the α,β-unsaturated γ-butyrolactone scaffold[ 9 , 10 ]. Particularly, butenolides possessing phenolic groups are considered for their broad spectrum of bioactivities, such as anti-plasmodial [ 11 ], anti-microbial [ 12 ], anti-inflammatory [ 8 ], α-glucosidase inhibitory [ 10 , 13 ], as well as antioxidant activities [ 14 ]. Given the increasing interest in natural antioxidants for clinical evaluation, it is imperative to biologically assess all currently recognized individual antioxidants. However, due to the time-intensive, costly, and technically demanding nature of biological evaluations, computational modeling presents an efficient approach for the preliminary assessment of both natural and synthesized antioxidants. Moreover, while experimental techniques provide only an overall measure of antioxidant activity, computational analyses make it possible to assess the contribution of each hydroxyl moiety, facilitating a comprehensive assessment of radical scavenging activity [ 15 ]. Consequently, numerous reputable studies have been conducted to thoroughly investigate the antioxidant properties of natural products using Density Functional Theory (DFT) methods [ 16 – 19 ]. An extensive review of the literature indicates that the radical scavenging properties of numerous species have been systematically investigated through computational methods; trans-resveratrol [ 20 ], gallic acid [ 21 ], natural depsidones [ 22 ], and syringic acid [ 23 ] are among the recently studied antioxidants. However, aspulvinone E [ 14 ] (4-hydroxy-5-(4-hydroxybenzylidene)-3-(4-hydroxyphenyl)furan-2(5H)-one), as a butenolide derivative, has not yet been modelled using quantum chemical tools. This study, utilizing the density functional theory (DFT) approach, evaluates the antioxidant activity and elucidates the radical scavenging mechanism of aspulvinone E . In order to understand the antioxidant efficacy of aspulvinone E in biological media, we have performed a comprehensive study to examine the reactivity of the compound toward hydroxyl (•OH) and hydroperoxyl (•OOH) radicals in implicit aqueous conditions. Computational methodology All geometries were optimized using the Gaussian 16 B.01 program package [ 24 ]. Calculations were carried out at M06-2X/6–31 + G(d,p) level of theory. An implicit solvent was used to mimic aqueous media by applying the SMD [ 25 ] solvation model. All possible mechanisms have been considered to elucidate the radical scavenging potential of the butenolide: hydrogen atom transfer (HAT), single-electron transfer-proton transfer (SET-PT), sequential proton loss-electron transfer (SPLET), and radical adduct formation (RAF). Bond dissociation energies (BDE) and ionization potentials (AIP) for aspulvinone E have been determined in a water-based environment. Furthermore, to clarify the process governing free radical scavenging, many other parameters were assessed, including the density plot for the molecular orbital of aspulvinone E , HOMO and LUMO energies, and their difference (E gap ). Hardness (ƞ)[ 26 ] reflects a molecule's resistance to electron distribution changes, which is calculated based on the energy difference between IP and EA [ 27 ], while softness (S)[ 28 ] indicates its ability to transfer electrons. Hardness and softness are defined by the following equations (Eq. (1) and Eq. (2)), respectively. Higher hardness reduces antioxidant activity, whereas greater softness enhances it [ 29 , 30 ]. Furthermore, hard molecules, with a large energy gap (E gap ), exhibit low charge transfer ability and weak antioxidant activity. In contrast, soft molecules have a smaller E gap , enabling efficient electron transfer and stronger radical scavenging capability [ 26 ]. ƞ = (IP ‒ EA) / 2 (1) S = 1 / (2 ƞ) (2) Electronegativity (χ) [ 31 ] is regarded as one of the most significant chemical descriptors for explaining the tendency of atoms to form molecular systems. It is calculated as the mean of the vertical ionization energy and the vertical electron affinity of a molecule (Eq. (3)) [ 32 ]. Consequently, the electronic chemical potential (µ) [ 26 ], formulated as the negative of electronegativity (Eq. (4)), determines electron movement from high to low potential regions. Higher µ values correlate with greater radical scavenging activity [ 33 ]. Χ = (IP + EA)/2 (3) µ = ‒ χ (4) Moreover, the electrophilicity index (ω) [ 28 ] quantifies the upper limit of electron transfer between donor and acceptor species (Eq. (5)). Compounds with higher ω values exhibit greater electrophilicity and enhanced antioxidant activity [ 29 ]. Ω = µ 2 / (2 ƞ) (5) Results and discussion The optimized structure of aspulvinone E is shown in Fig. 1 . In accordance with the most stable molecular geometry obtained from conformational analysis, it has a fully planar structure (Fig. 1 ). Numerous potential reactions between aspulvinone E and free radicals are possible in a water-based environment. Elaborating on these reactions is key to understanding their antioxidant activity [ 20 ]. In particular, reactions related to antioxidant activity can be grouped into two basic types of mechanisms: (i) hydrogen atom abstraction and (ii) radical addition (radical adduct formation, RAF) [ 21 ] (Fig. 1 ). Hydrogen atom abstraction can occur according to three different pathways: direct hydrogen atom transfer (HAT), single-electron transfer-proton transfer (SET-PT), and sequential proton loss-electron transfer (SPLET) [ 34 ]. All the above-mentioned mechanisms have been modeled in aqueous media. Due to its mild reactivity, the •OOH radical is regarded as a model free radical for assessing the antiradical activities of organic compounds [ 35 ]. Studies on the radical scavenging ability of natural products against other common reactive oxygen species, such as •OH, are critical to provide useful information regarding their antioxidant activities. Therefore, the reactivity of aspulvinone E was also modeled against •OH radical following the main mechanisms in water: hydrogen atom transfer (HAT) and radical adduct formation (RAF) [ 36 ]. Because each hydroxyl (‒OH) of the molecule can show dissimilar activity in scavenging free radicals, H-atom transfer reactions between an •OH and •OOH species and hydroxyl groups at different positions were studied. To be more specific, we have considered radical addition to accessible C = C bond carbon atoms (C1, C2, C3), as well as H abstraction from hydroxyl groups (from positions H-1, H-2, and H-3) (Fig. 1 ). HAT Mechanism The reactivity of the •OOH and •OH radicals was evaluated through HAT mechanism and corresponding optimized structures for the transition states (TS) are presented in Fig. 2 . For •OOH radical it was found that the activation Gibbs free energy of H-abstraction from position H-3 is 20.22 kJ mol − 1 (Table 1 ), which is lower than those corresponding to positions H-1 (44.91 kJ mol − 1 ) and H-2 (39.68 kJ mol − 1 ). The same trend was observed in the results obtained from •OH radical; the activation Gibbs free energy of H-abstraction from position H-3 is 0.92 kJ mol − 1 , which is lower than those corresponding to positions H-1 (3.55 kJ mol − 1 ) and H-2 (7.26 kJ mol − 1 ) (Table 1 ). The H-3 hydroxyl group is certainly the most reactive site because the formed radical at this position can be stabilized strongly by a longer-range resonance between the two aromatic rings. Table 1 Energetics (kJ mol − 1 ) and kinetics (L mol − 1 s − 1 ) for hydrogen (H-1, H-2, and H-3) transfer reactions to HOO• and HO• (M06-2X/6–31 + G(d) level, 298.15 K, in water polarized implicit solvent medium). HOO• \(\:{\varvec{\Delta\:}\mathbf{G}}_{\mathbf{r}\mathbf{x}\mathbf{n}}\) \(\:{\varvec{\Delta\:}\mathbf{G}}^{\ddagger}\) k water Wigner Factor H‒1 3.02 44.91 1.25E + 07 5.99 H‒2 -5.10 39.68 9.95E + 07 5.78 H‒3 -38.40 20.22 3.36E + 11 7.61 HO• H‒1 -129.46 3.55 1.57E + 14 4.28 H‒2 -128.11 7.26 6.16E + 13 7.48 H‒3 -170.80 0.92 4.09E + 14 3.85 Furthermore, radical stabilization energy (RSE) [ 37 ] values of radical structures formed after the HAT mechanism are presented in Table S1 (Supporting Information). The formed radical at position 3 (H-3) exhibits the highest RSE value (137.68 kJ mol − 1 ), indicating that this radical structure is more stable than other radicals formed after transferring H-1 and H-2 hydrogen atoms. Marino et al. [ 21 ] reported related to the antioxidant activity of gallic acid that the Gibbs free energy of activation for H-abstraction by •OOH radical from the phenolic -OH group in a water-based environment was approximately 50.07 kJ mol − 1 . In another research, Vo et al. [ 23 ] worked on the antioxidant activity of syringic acid. They found that in an aqueous environment, the Gibbs free energy of H-abstraction from the phenolic -OH group by •OH radical is 25.96 kJ mol − 1 . Our study has revealed that the activation energies of the HAT mechanism are lower than those reported in the literature. Consequently, within the framework of the HAT mechanism, these findings suggest that the aspulvinone E possesses higher reactivity and superior antioxidant properties relative to gallic acid and syringic acid. RAF Mechanism Within the scope of this study, the radical adduct formation (RAF) process with •OOH and •OH addition at C1, C2, and C3 positions was investigated, and corresponding optimized structures for the transition states (TS) are presented in Fig. 3. Calculated Gibbs free energies are reported in Table 2 . The Cartesian coordinates for all the RAF transition configurations can be found in Table S3 (Supporting Information section). Table 2 Energetics (kJ mol − 1 ) and kinetics (L mol − 1 s − 1 ) for HOO• and HO• addition reactions to C-1, C-2, and C-3 (M06-2X/6–31 + G(d) level, 298.15 K, in water polarized implicit solvent medium). HOO• \(\:{\varvec{\Delta\:}\mathbf{G}}_{\mathbf{r}\mathbf{x}\mathbf{n}}\) \(\:{\varvec{\Delta\:}\mathbf{G}}^{\ddagger}\) k water C‒1 -67.33 27.90 1.99E + 09 C‒2 -57.39 24.07 9.35E + 09 C‒3 -36.82 38.51 2.76E + 07 HO• C‒1 -138.00 4.08 1.20E + 12 C‒2 -103.49 11.12 7.01E + 10 C‒3 -140.25 12.28 4.38E + 10 The transition states (TSs) for the addition path at C1 and C2 positions are earlier than at C3 position, for both reactions with •OOH and •OH radicals. This suggests that position C3 should be the least reactive site via RAF. In addition, all the TS for the •OH reactions are earlier than the corresponding ones involving •OOH, which is in agreement with the relative reactivity difference of these radicals. Calculations on the HAT reaction mechanism kinetics revealed that the rate constants for •OOH radical reactions vary from 7 to 11 orders of magnitude. The fastest reaction occurs at the H-3 position, and the calculated rate coefficient is 3.36 × 10 11 L mol − 1 s − 1 . Moreover, the more reactive •OH radical exhibits a remarkably diffusion-controlled reaction; the rate constants of all hydrogen atom transfer reactions are greater than 11 orders of magnitude. Additionally, calculations on the RAF mechanism kinetics (Table 2 ) exhibited that the rate constants for •OOH radical reactions vary from 7 to 9 orders of magnitude. The slowest addition occurs at the C-3 position with the rate coefficient 2.76 + 10 7 L mol − 1 s − 1 . Attacking the other position shows relatively faster reactions; the rate coefficients are 1.99 + 10 9 and 9.35 + 10 9 L mol − 1 s − 1 at C-1 and C-2, respectively. Moreover, the addition reaction of •OH radical is diffusion-controlled reaction rates at any accessible C = C double bond positions. We have considered that reactions take place through a typical complex two-step mechanism. The initial phase involves the generation of a pre-reactive complex in equilibrium with the reactants, followed by a second, irreversible stage leading to product formation [ 20 ]. SET-PT and SPLET Mechanisms The SET-PT mechanism involves two primary reactions; the first reaction requires an adiabatic ionization potential (AIP) energy, which refers to the lowest amount of energy necessary to detach an electron from molecule or atom in its ground state, without any excess vibrational or rotational excitation. The second reaction is characterized by proton dissociation energy (PDE) of cationic antioxidant radical (Fig. 4 ). Furthermore, the SPLET mechanism's first step entails dissociating an antioxidant's phenolic-OH group into an anion and a proton, with proton affinity (PA) quantifying this process. The next step entails the anion reacting with a free radical, which results in the formation of a neutral species and a phenolic antioxidant radical. Throughout this stage, an electron transfer occurs from the anion toward the free radical, which is characterized by electron transfer enthalpy (ETE) [ 28 , 40 ] (Fig. 5 ). In the context of the SET-PT and SPLET mechanisms, as mentioned above, AIP and PA represent the initial steps, serving as crucial determinants. Consequently, BDE, AIP, and PA numerical values are frequently employed to identify the thermodynamically favored reaction pathway. Additionally, computed BDE values may be useful in determining if the HAT mechanism is kinetically preferred; the more likely the associated mechanism, the lower the energy of this descriptor [ 29 ]. In molecules exhibiting high AIP values, electron donation is significantly challenging. The studied molecule has a PA value exceeding its AIP, indicating that the SET-PT mechanism is more likely than the SPLET pathway. However, calculations show that the values obtained for BDE are considerably less than those determined for AIP and PA (Table S2). Therefore, from the energetic point of view, HAT is the preferred reaction path in the water solvent medium. Analysis with Descriptors The antioxidant property of aspulvinone E was also evaluated based on various quantum chemical descriptors and compared with the findings in the literature (Table 3 and Table 4 ). The main parameters used in this evaluation include ionization potential (IP), electron affinity (EA), chemical hardness (η), softness (S), electronegativity (χ), chemical potential (µ), electrophilic index (ω), and frontier molecular orbital energies (HOMO, LUMO, and their energy difference E gap ). A higher IP signifies a reduced tendency for electron donation. Conversely, molecules exhibiting higher EA values are more prone to electron gain than those with lower EA [ 28 ]. Compared to the data reported in the literature (Table 3 ), aspulvinone E exhibits a lower IP value than apigenin [ 15 ] and aloe-emodin[ 28 ] antioxidants, shows electron-donating capability towards radical species, and indicates its higher antioxidant activity. On the contrary, resveratrol [ 30 ] has the lowest value compared to aspulvinone E , apigenin, and aloe-emodin. The highest electron affinity was found in aloe-emodin [ 28 ], indicates the highest capacity to extract an electron from a radical species. Furthermore, the greater antioxidant property of aspulvinone E compared to apigenin and resveratrol is evident from the fact that its EA value is higher than that of apigenin [ 15 ] and resveratrol [ 30 ]. Table 3 IE and EA parameters (kJ mol − 1 ) of aspulvinone E compared with the data presented in the literature (in PCM medium with implicit water). This Study Apigenin [ 15 ] Aloe-emodin [ 28 ] Quercetin [ 30 ] Resveratrol [ 20 ] M062X/6–31 + G* B3LYP/6-311G(d,p) B3LYP/6–311 + + G** B3LYP/6-311G(d,p) B3LYP/6-311G(d,p) IP 586.88 593.88 637.80 524.92 520.11 EA 250.75 190.04 300.08 230.84 203.18 The computed parameters based on descriptors and frontier orbital theory analysis are presented in Table 4 . When evaluated in terms of chemical hardness and softness, aspulvinone E exhibits low hardness (η ≈ 1.74 eV) and high softness (S ≈ 0.29 1/eV) like aloe-emodin, indicating that these molecules may be more reactive and therefore more potent antioxidant candidates than apigenin and quercetin. Electronegativity (χ) and chemical potential (µ) parameters are used to determine molecule’s electron-withdrawing and electron-donating tendencies. In terms of antioxidant effect, compounds with high electron-donating tendencies are preferred. In this context, quercetin has the lowest electronegativity and the least negative chemical potential, while aspulvinone E has a higher electronegativity compared to quercetin and apigenin, which means that it will exhibit a relatively weaker profile in terms of electron donation tendency. When the electrophilic indices (ω) are evaluated, it is seen that aloe-emodin has the highest value (6.75 eV) indicating that it has a very high capacity to capture nucleophilic free radicals. Therefore, it shows less reactivity when reacting with electrophilic radicals such as HO• and CH 3 O•. Similarly, aspulvinone E has a relatively high value (5.51 eV), suggesting the molecule can act as an electron acceptor. Frontier orbital energies (HOMO, LUMO) and the energy difference between them (E gap ) can be involved in determining the kinetic stability and reactivity of molecules. High HOMO energy represents the electron-donating capacity of the molecule, while a low HOMO-LUMO gap (Egap) means higher chemical reactivity. In this respect, quercetin and aloe-emodin have the lowest Egap values ​​and stand out as the most reactive and free radical scavenging compounds. In contrast, aspulvinone E has the lowest HOMO and highest Egap values, making it the least reactive molecule with the lowest electron-donating capacity. This result is also consistent with the relatively high electrophilic index (ω) value of aspulvinone E . When a general evaluation is made, aloe-emodin has a more balanced and powerful antioxidant profile in terms of studied descriptors. It can be said that it shows high free radical scavenging capacity with low hardness and Egap. On the other hand, aspulvinone E offers a strong antioxidant potential in some aspects (hardness and softness). However, its overall reactivity can be considered as limited due to its high HOMO-LUMO gap and low HOMO energy. This suggests that it may be reluctant to donate electrons and have a more kinetically stable structure. Apigenin and quercetin, on the other hand, show lower antioxidant activity with their lower electrophilicity and harder structures; however, quercetin is in an advantageous position in terms of HOMO level and Egap, and is expected to exhibit a remarkable performance, especially in electron donation-based mechanisms. As a result, in light of the descriptors studied, it can be thought that aspulvinone E , despite its potential, may exhibit a limited antioxidant capacity due to its specific electronic properties; however, possessing relatively lower hardness and higher softness strongly enhances its antioxidant capacity. Table 4 Parameters (eV) computed to determine and describe the mechanism involved in free radical scavenging compared with the data presented in the literature. This Study Apigenin [ 15 ] Aloe-emodin [ 28 ] Quercetin [ 30 ] ƞ 1.74 3.30 1.74 3.23 S 0.29 0.15 0.28 0.15 χ x 4.34 4.19 4.85 3.99 µ -4.34 -4.19 -4.85 -3.99 ω 5.51 2.66 6.75 2.47 HOMO -6.94 -6.15 -6.6 -5.69 LUMO -1.69 -1.98 -3.11 -2.30 E gap 5.26 4.17 3.48 3.38 It should be emphasized that Apigenin, Resveratrol, and Quercetin, owing to their pronounced antioxidant efficacy, have undergone successful commercial development. These compounds exhibit sustained market presence and demonstrate medically relevant applications increasingly supported by scientific research [ 41 – 43 ]. Frontier Orbital Theory Analysis To investigate the correlation between electron delocalization and the reactivity of the aspulvinone E structure, we generate density plots of the HOMO and LUMO compositions (Fig. 6 ). Plotting HOMO orbitals can also be utilized to find locations with a high distribution of HOMO electronic density. In biological systems, electrophilic free radical attack preferentially targets the regions of the molecule where the HOMO electron density is highest[ 33 ]. As shown in Fig. 6 , in the aspulvinone E structure, HOMO and LUMO are largely delocalized throughout the molecule except O3 atom for HOMO and C1, C2, C15, C16, and O3 atoms for LUMO. The presence of HOMO density facilitates the formation of sites sensitive to interactions with free radicals, thereby enhancing the antioxidant properties of butenolide. Analysis of the HOMO orbital in the non-radical form of aspulvinone E reveals that electron density is predominantly localized on the phenyl and furanone rings. At the same time, it is mainly located on the furanone ring for LUMO. This finding emphasizes the importance of the unsaturated carbon bonds in the furanone side for the radical attack with the RAF mechanism and the critical role of hydroxyl groups in scavenging free radicals by the HAT mechanism [ 28 ]. Conclusion The antioxidant activity of aspulvinone E was thoroughly examined through quantum chemical approach. Thermodynamically and kinetically revealed the H-3 hydroxyl as the most reactive site for HAT, with significantly lower activation Gibbs free energy values for hydrogen abstraction by •OOH (20.22 kJ mol⁻¹) and •OH radicals (0.92 kJ mol⁻¹), compared to H-1 and H-2 positions. The radical formed at H-3 showed the highest stabilization energy (RSE = 137.68 kJ mol⁻¹), indicating superior stability via extended conjugation throughout aromatic rings. Kinetic studies showed that HAT at H-3 yielded the highest reaction rate for •OOH radicals (k = 3.36 × 10¹¹ L mol⁻¹ s⁻¹), while all •OH-mediated HAT processes were diffusion-controlled with rate constants exceeding 10¹¹ L mol⁻¹ s⁻¹. RAF analysis further confirmed the positional influence on reactivity: C1 addition by •OOH was the most favorable (ΔG = − 67.33 kJ mol⁻¹), while •OH radical addition at C3 yielded the highest exergonicity (ΔG = − 140.25 kJ mol⁻¹). The molecule’s moderate ionization potential and elevated electron affinity suggest promising free radical interaction capacity, making it a viable electron donor. Furthermore, electronic structure descriptors indicate low hardness (η ≈ 1.74 eV), high softness (S ≈ 0.29 1/eV), and moderate electrophilicity (ω = 5.51 eV), positioning the molecule as a responsive electron donor with favorable radical-scavenging attributes. The HOMO density distribution predominantly over the phenyl and furanone moieties suggests targeted radical scavenging at these sites, a feature likely enhanced by the hydroxyl group presence. Collectively, these findings support aspulvinone E ’s potential as a selective and stable antioxidant. While its reactivity may be mechanism-dependent, particularly favoring HAT, the compound’s distinctive electronic attributes warrant further biological assessment and potential therapeutic development. Declarations Author contribution B. G. N. contributed to the investigation, calculations, data curation, writing the original draft, formal analysis, and visualization. I. D. was involved in methodology, investigation, calculations, validation, resources, supervision, and writing review & editing. The authors were both involved in reviewing. Corresponding authors: Belma Gjergjizi Nallbani and Isa Degirmenci Acknowledgment The authors are thankful to TUBITAK ULAKBIM and Ondokuz Mayıs University; the calculations reported in this research were partially performed at TUBITAK ULAKBIM, High Performance and Grid Computing Center (TRUBA resources), and Ondokuz Mayıs University. Conflict of interest There is no conflict of interest for this study. Ethical Approval This declaration is “not applicable.” Funding This declaration is “not applicable.” This study was not supported by any funding. Availability of data and materials All optimized geometries and relevant data generated and analyzed throughout this study are included in the manuscript and its supplementary information. References Rahaman MM, Hossain R, Herrera-Bravo J, Islam MT, Atolani O, Adeyemi OS, Owolodun OA, Kambizi L, Daştan SD, Calina D, Sharifi‐Rad J (2023) Natural antioxidants from some fruits, seeds, foods, natural products, and associated health benefits: An update. Food Sci Nutr 11:1657–1670. https://doi.org/10.1002/fsn3.3217 Xu X, Liu A, Hu S, Ares I, Martínez-Larrañaga M-R, Wang X, Martínez M, Anadón A, Martínez M-A (2021) Synthetic phenolic antioxidants: Metabolism, hazards and mechanism of action. Food Chem 353:129488. https://doi.org/10.1016/j.foodchem.2021.129488 Chaudhary P, Janmeda P, Docea AO, Yeskaliyeva B, Abdull Razis AF, Modu B, Calina D, Sharifi-Rad J (2023) Oxidative stress, free radicals and antioxidants: potential crosstalk in the pathophysiology of human diseases. Front Chem 11. https://doi.org/10.3389/fchem.2023.1158198 Parcheta M, Świsłocka R, Orzechowska S, Akimowicz M, Choińska R, Lewandowski W (2021) Recent Developments in Effective Antioxidants: The Structure and Antioxidant Properties. Materials 14:1984. https://doi.org/10.3390/ma14081984 Cipolletti M, Solar Fernandez V, Montalesi E, Marino M, Fiocchetti M (2018) Beyond the Antioxidant Activity of Dietary Polyphenols in Cancer: the Modulation of Estrogen Receptors (ERs) Signaling. Int J Mol Sci 19:2624. https://doi.org/10.3390/ijms19092624 Gulcin İ (2020) Antioxidants and antioxidant methods: an updated overview. Arch Toxicol 94:651–715. https://doi.org/10.1007/s00204-020-02689-3 Liao G, Wu P, Xue J, Liu L, Li H, Wei X (2018) Asperimides A–D, anti-inflammatory aromatic butenolides from a tropical endophytic fungus Aspergillus terreus. Fitoterapia 131:50–54. https://doi.org/10.1016/j.fitote.2018.10.011 Guo F, Li Z, Xu X, Wang K, Shao M, Zhao F, Wang H, Hua H, Pei Y, Bai J (2016) Butenolide derivatives from the plant endophytic fungus Aspergillus terreus. Fitoterapia 113:44–50. https://doi.org/10.1016/j.fitote.2016.06.014 Peng Q, Chen W, Lin X, Xiao J, Liu Y, Zhou X (2022) Butenolides from the Coral-Derived Fungus Aspergillius terreus SCSIO41404. Mar Drugs 20:212. https://doi.org/10.3390/md20030212 Elhady SS, Alshobaki NM, Elfaky MA, Koshak AE, Alharbi M, Abdelhameed RFA, Darwish KM (2023) Deciphering Molecular Aspects of Potential α-Glucosidase Inhibitors within Aspergillus terreus: A Computational Odyssey of Molecular Docking-Coupled Dynamics Simulations and Pharmacokinetic Profiling. Metabolites 13:942. https://doi.org/10.3390/metabo13080942 Haritakun R, Rachtawee P, Chanthaket R, Boonyuen N, Isaka M (2010) Butyrolactones from the Fungus Aspergillus terreus BCC 4651. Chem Pharm Bull (Tokyo) 58:1545–1548. https://doi.org/10.1248/cpb.58.1545 Zhang YY, Zhang Y, Yao Y-B, Lei X-L, Qian Z-J (2018) Butyrolactone-I from Coral-Derived Fungus Aspergillus terreus Attenuates Neuro-Inflammatory Response via Suppression of NF-κB Pathway in BV-2 Cells. Mar Drugs 16:202. https://doi.org/10.3390/md16060202 Wu Y, Chen Y, Huang X, Pan Y, Liu Z, Yan T, Cao W, She Z (2018) α-Glucosidase Inhibitors: Diphenyl Ethers and Phenolic Bisabolane Sesquiterpenoids from the Mangrove Endophytic Fungus Aspergillus flavus QQSG-3. Mar Drugs 16. https://doi.org/10.3390/md16090307 Sun Y, Liu J, Li L, Gong C, Wang S, Yang F, Hua H, Lin H (2018) New butenolide derivatives from the marine sponge-derived fungus Aspergillus terreus. Bioorg Med Chem Lett 28:315–318. https://doi.org/10.1016/j.bmcl.2017.12.049 Sadasivam K, Kumaresan R (2011) A comparative DFT study on the antioxidant activity of apigenin and scutellarein flavonoid compounds. Mol Phys 109:839–852. https://doi.org/10.1080/00268976.2011.556576 Vo QV, Tam NM, Bay M, Van, Mechler A (2020) The radical scavenging activity of natural ramalin: A mechanistic and kinetic study. Chem Phys Lett 739:137004. https://doi.org/10.1016/j.cplett.2019.137004 Vo QV, Gon T, Van BM, Van, Mechler A (2019) Antioxidant Activities of Monosubstituted Indolinonic Hydroxylamines: A Thermodynamic and Kinetic Study. J Phys Chem B 123:10672–10679. https://doi.org/10.1021/acs.jpcb.9b08912 Galano A, Raúl Alvarez-Idaboy J (2019) Computational strategies for predicting free radical scavengers’ protection against oxidative stress: Where are we and what might follow? Int J Quantum Chem 119. https://doi.org/10.1002/qua.25665 Boulebd H (2020) Theoretical insights into the antioxidant activity of moracin T. Free Radic Res 54:221–230. https://doi.org/10.1080/10715762.2020.1747616 Iuga C, Alvarez-Idaboy JR, Russo N (2012) Antioxidant Activity of trans -Resveratrol toward Hydroxyl and Hydroperoxyl Radicals: A Quantum Chemical and Computational Kinetics Study. J Org Chem 77:3868–3877. https://doi.org/10.1021/jo3002134 Marino T, Galano A, Russo N (2014) Radical Scavenging Ability of Gallic Acid toward OH and OOH Radicals. Reaction Mechanism and Rate Constants from the Density Functional Theory. J Phys Chem B 118:10380–10389. https://doi.org/10.1021/jp505589b Bay M, Van, Nam PC, Quang DT, Mechler A, Hien NK, Hoa NT, Vo QV (2020) Theoretical Study on the Antioxidant Activity of Natural Depsidones. ACS Omega 5:7895–7902. https://doi.org/10.1021/acsomega.9b04179 Vo QV, Bay M, Van, Nam PC, Quang DT, Flavel M, Hoa NT, Mechler A (2020) Theoretical and Experimental Studies of the Antioxidant and Antinitrosant Activity of Syringic Acid. J Org Chem 85:15514–15520. https://doi.org/10.1021/acs.joc.0c02258 Frisch MJ (2016) Gaussian 16, Revision B.01. Gaussian. Inc., Wallingford CT Marenich AV, Cramer CJ, Truhlar DG (2009) Universal Solvation Model Based on Solute Electron Density and on a Continuum Model of the Solvent Defined by the Bulk Dielectric Constant and Atomic Surface Tensions. J Phys Chem B 113:6378–6396. https://doi.org/10.1021/jp810292n Chandrakumar KRS, Pal S (2002) The Concept of Density Functional Theory Based Descriptors and its Relation with the Reactivity of Molecular Systems: A Semi-Quantitative Study. Int J Mol Sci 3:324–337. https://doi.org/10.3390/i3040324 Marenich AV, Cramer CJ, Truhlar DG (2009) Universal Solvation Model Based on Solute Electron Density and on a Continuum Model of the Solvent Defined by the Bulk Dielectric Constant and Atomic Surface Tensions. J Phys Chem B 113:6378–6396. https://doi.org/10.1021/jp810292n Reza Nazifi SM, Asgharshamsi MH, Dehkordi MM, Zborowski KK (2019) Antioxidant properties of Aloe vera components: a DFT theoretical evaluation. Free Radic Res 53:922–931. https://doi.org/10.1080/10715762.2019.1648798 Foti MC, Daquino C, Geraci C (2004) Electron-Transfer Reaction of Cinnamic Acids and Their Methyl Esters with the DPPH• Radical in Alcoholic Solutions. J Org Chem 69:2309–2314. https://doi.org/10.1021/jo035758q Lu L, Qiang M, Li F, Zhang H, Zhang S (2014) Theoretical investigation on the antioxidative activity of anthocyanidins: A DFT/B3LYP study. Dyes Pigm 103:175–182. https://doi.org/10.1016/j.dyepig.2013.12.015 Murphy LR, Meek TL, Allred AL, Allen LC (2000) Evaluation and Test of Pauling’s Electronegativity Scale. J Phys Chem A 104:5867–5871. https://doi.org/10.1021/jp000288e Mulliken RS (1934) A New Electroaffinity Scale; Together with Data on Valence States and on Valence Ionization Potentials and Electron Affinities. J Chem Phys 2:782–793. https://doi.org/10.1063/1.1749394 Akhtari K, Hassanzadeh K, Fakhraei B, Fakhraei N, Hassanzadeh H, Zarei SA (2013) A density functional theory study of the reactivity descriptors and antioxidant behavior of Crocin. Comput Theor Chem 1013:123–129. https://doi.org/10.1016/j.comptc.2013.03.015 Siddeeg A, AlKehayez NM, Abu-Hiamed HA, Al-Sanea EA, AL-Farga AM (2021) Mode of action and determination of antioxidant activity in the dietary sources: An overview. Saudi J Biol Sci 28:1633–1644. https://doi.org/10.1016/j.sjbs.2020.11.064 Perez-Gonzalez A, Muñoz-Rugeles L, Alvarez-Idaboy JR (2014) Tryptophan: antioxidant or target of oxidative stress? A quantum chemistry elucidation. RSC Adv 4:56128–56131. https://doi.org/10.1039/C4RA11635F Ngoc TD, Thi Ha MV, Le TN, Thi HV, Anh Nguyen T, Van, Mechler A, Hoa NT, Vo QV (2022) A Potent Antioxidant Sesquiterpene, Abelsaginol, from Abelmoschus sagittifolius: Experimental and Theoretical Insights. ACS Omega 7:24004–24011. https://doi.org/10.1021/acsomega.2c02974 Hioe J, Zipse H (2010) Radical stability and its role in synthesis and catalysis. Org Biomol Chem 8:3609. https://doi.org/10.1039/c004166a Wang A, Lu Y, Du X, Shi P, Zhang H (2018) A theoretical study on the antioxidant activity of Uralenol and Neouralenol scavenging two radicals. Struct Chem 29:1067–1075. https://doi.org/10.1007/s11224-018-1090-8 Pryor WA (1988) Why is the hydroxyl radical the only radical that commonly adds to DNA? Hypothesis: It has a rare combination of high electrophilicity, high thermochemical reactivity, and a mode of production that can occur near DNA. Free Radic Biol Med 4:219–223. https://doi.org/10.1016/0891-5849(88)90043-3 Pei L (2023) Theoretical Study on Methylated Resveratrol Analogues towards the Antioxidant Activity and Mechanisms: Understanding the Structure–Activity Relationship. Russ J Phys Chem A 97:1121–1127. https://doi.org/10.1134/S0036024423060171 Galiniak S, Aebisher D, Bartusik-Aebisher D (2019) Health benefits of resveratrol administration. Acta Biochim Pol. https://doi.org/10.18388/abp.2018_2749 Salehi B, Venditti A, Sharifi-Rad M, Kręgiel D, Sharifi-Rad J, Durazzo A, Lucarini M, Santini A, Souto EB, Novellino E, Antolak H, Azzini E, Setzer WN, Martins N (2019) The Therapeutic Potential of Apigenin. Int J Mol Sci 20:1305. https://doi.org/10.3390/ijms20061305 Yang D, Wang T, Long M, Li P (2020) Quercetin: Its Main Pharmacological Activity and Potential Application in Clinical Medicine. Oxid Med Cell Longev 2020:1–13. https://doi.org/10.1155/2020/8825387 Additional Declarations No competing interests reported. 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11:06:37","extension":"png","order_by":33,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":9457,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage9.png","url":"https://assets-eu.researchsquare.com/files/rs-7678529/v1/429de14feb1b71a1bd5c5868.png"},{"id":93675886,"identity":"e4b37350-9ffc-4e36-a745-014a8c646dce","added_by":"auto","created_at":"2025-10-16 11:06:37","extension":"xml","order_by":34,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":128357,"visible":true,"origin":"","legend":"","description":"","filename":"9d9b84879a8f40ccad37d531b17057531structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-7678529/v1/ac0e5eeb5fecaed9df70136f.xml"},{"id":93675887,"identity":"39731bd8-c0e1-412c-bb86-f7e435671918","added_by":"auto","created_at":"2025-10-16 11:06:37","extension":"html","order_by":35,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":137044,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7678529/v1/4ef69d75580e1e4425dc9115.html"},{"id":93675843,"identity":"9c189542-f392-4874-adee-158572fa4f8c","added_by":"auto","created_at":"2025-10-16 11:06:36","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":98401,"visible":true,"origin":"","legend":"\u003cp\u003eOptimized structure of \u003cem\u003easpulvinone E\u003c/em\u003e in water (top) and schematic representation of where the modelled reactions occur for HAT (H-1, H-2, H-3) and RAF (C1, C2, C3) mechanisms (bottom).\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7678529/v1/b6a5f1c6b296d4d7828806a6.png"},{"id":93675847,"identity":"3e5c9e65-d0c2-4c14-8b7e-8b9186d58454","added_by":"auto","created_at":"2025-10-16 11:06:36","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":122538,"visible":true,"origin":"","legend":"\u003cp\u003eOptimized structures for transition states (TS) in the HAT mechanism with •OOH and •OH radicals.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7678529/v1/b4dad3716a1e1aa7d05836fe.png"},{"id":93676727,"identity":"b971d949-9314-4433-8e31-a840a0ae0d87","added_by":"auto","created_at":"2025-10-16 11:14:36","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":176488,"visible":true,"origin":"","legend":"\u003cp\u003eOptimized structures for transition states (TS) in the RAF mechanism with •OOH and •OH radicals in M06-2X/6-31+G(d) level; a) C1, b) C2, and c) C3 addition pathways.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7678529/v1/5ee957c55df594085c546fd6.png"},{"id":93677059,"identity":"ef8c4c82-eecb-4a00-bd5f-2ee4652bb8d4","added_by":"auto","created_at":"2025-10-16 11:22:36","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":44387,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic representation of AIP and PDE steps of the SET-PT mechanism.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-7678529/v1/69546cffba769d8770234791.png"},{"id":93677928,"identity":"5096ccc3-9387-49fc-9966-ace44dabab0d","added_by":"auto","created_at":"2025-10-16 11:30:36","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":23737,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic representation of ETE steps of the SPLET mechanism.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-7678529/v1/ee89b1afc27ff02a906fc2f8.png"},{"id":93675860,"identity":"b61e60f1-40d8-4439-8790-a82ed5f7c0bc","added_by":"auto","created_at":"2025-10-16 11:06:37","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":329151,"visible":true,"origin":"","legend":"\u003cp\u003eDensity distributions of LUMO (top) and HOMO (bottom) for \u003cem\u003easpulvinone \u003c/em\u003eEstructure.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-7678529/v1/5f9f1e5fa39cccec503599a6.png"},{"id":103765593,"identity":"c74f2c14-72a4-4f21-88f9-89cf1a9d3d46","added_by":"auto","created_at":"2026-03-02 16:05:25","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1490355,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7678529/v1/a50881d5-ee46-41ac-b83e-ced016437ab1.pdf"},{"id":93675845,"identity":"232c6638-bd6a-4cde-b099-94d07cac14c2","added_by":"auto","created_at":"2025-10-16 11:06:36","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":36212,"visible":true,"origin":"","legend":"","description":"","filename":"SupportingInformation0917.docx","url":"https://assets-eu.researchsquare.com/files/rs-7678529/v1/664c78eba78f37cba54812a6.docx"},{"id":93675852,"identity":"64547bdd-3f09-4141-aef7-17e8c75eef45","added_by":"auto","created_at":"2025-10-16 11:06:36","extension":"png","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":178217,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eTable of Contents\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7678529/v1/92328ffc2b680842150cd7c2.png"}],"financialInterests":"No competing interests reported.","formattedTitle":"Computational Study: Antioxidant Activity of Aspulvinone E Toward Hydroperoxyl and Hydroxyl Radicals","fulltext":[{"header":"Introduction","content":"\u003cp\u003eAntioxidants are either naturally occurring [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e] or synthetically produced [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e] substances that prevent the process of oxidation, which generates free radicals. These free radicals have the potential to inflict cellular damage. They are linked to the progression of aging as well as several pathologies, including cancer, cardiovascular disorders, and Alzheimer's disease [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Essentially, antioxidants function as a protective mechanism, neutralizing free radicals and thus safeguarding cellular integrity.\u003c/p\u003e\u003cp\u003ePolyphenols are widely recognized for their antioxidant properties [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. According to further reports, depending on their chemical structures, the polyphenols affect how quickly they are absorbed and circulated in the blood plasma [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Moreover, the antioxidant activity of polyphenols is influenced by the abundance and location of -OH groups attached to the aromatic ring[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Therefore, emphasizing the molecular structure's influence on the compounds' antioxidant efficacy is extremely important.\u003c/p\u003e\u003cp\u003eIn recent years, considerable interest has been shown in discovering alternative natural and safe sources of antioxidants for food applications, with a particular emphasis on those derived from plants. For example, fungi have also been acknowledged as an abundant source of novel bioactive compounds[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. \u003cem\u003eAspergillus terreus\u003c/em\u003e is a common fungus extensively used in the chemical and pharmaceutical industries [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. \u003cem\u003eAspergillus\u003c/em\u003e species are a common source of butenolides, also termed butyrolactones, that exhibit the α,β-unsaturated γ-butyrolactone scaffold[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Particularly, butenolides possessing phenolic groups are considered for their broad spectrum of bioactivities, such as anti-plasmodial [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e], anti-microbial [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e], anti-inflammatory [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e], α-glucosidase inhibitory [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], as well as antioxidant activities [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eGiven the increasing interest in natural antioxidants for clinical evaluation, it is imperative to biologically assess all currently recognized individual antioxidants. However, due to the time-intensive, costly, and technically demanding nature of biological evaluations, computational modeling presents an efficient approach for the preliminary assessment of both natural and synthesized antioxidants. Moreover, while experimental techniques provide only an overall measure of antioxidant activity, computational analyses make it possible to assess the contribution of each hydroxyl moiety, facilitating a comprehensive assessment of radical scavenging activity [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Consequently, numerous reputable studies have been conducted to thoroughly investigate the antioxidant properties of natural products using Density Functional Theory (DFT) methods [\u003cspan additionalcitationids=\"CR17 CR18\" citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eAn extensive review of the literature indicates that the radical scavenging properties of numerous species have been systematically investigated through computational methods; trans-resveratrol [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e], gallic acid [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e], natural depsidones [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e], and syringic acid [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e] are among the recently studied antioxidants. However, \u003cem\u003easpulvinone E\u003c/em\u003e [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] (4-hydroxy-5-(4-hydroxybenzylidene)-3-(4-hydroxyphenyl)furan-2(5H)-one), as a butenolide derivative, has not yet been modelled using quantum chemical tools.\u003c/p\u003e\u003cp\u003eThis study, utilizing the density functional theory (DFT) approach, evaluates the antioxidant activity and elucidates the radical scavenging mechanism of \u003cem\u003easpulvinone E\u003c/em\u003e. In order to understand the antioxidant efficacy of \u003cem\u003easpulvinone E\u003c/em\u003e in biological media, we have performed a comprehensive study to examine the reactivity of the compound toward hydroxyl (\u0026bull;OH) and hydroperoxyl (\u0026bull;OOH) radicals in implicit aqueous conditions.\u003c/p\u003e"},{"header":"Computational methodology","content":"\u003cp\u003eAll geometries were optimized using the Gaussian 16 B.01 program package [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. Calculations were carried out at M06-2X/6\u0026ndash;31\u0026thinsp;+\u0026thinsp;G(d,p) level of theory. An implicit solvent was used to mimic aqueous media by applying the SMD [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e] solvation model. All possible mechanisms have been considered to elucidate the radical scavenging potential of the butenolide: hydrogen atom transfer (HAT), single-electron transfer-proton transfer (SET-PT), sequential proton loss-electron transfer (SPLET), and radical adduct formation (RAF). Bond dissociation energies (BDE) and ionization potentials (AIP) for \u003cem\u003easpulvinone E\u003c/em\u003e have been determined in a water-based environment. Furthermore, to clarify the process governing free radical scavenging, many other parameters were assessed, including the density plot for the molecular orbital of \u003cem\u003easpulvinone E\u003c/em\u003e, HOMO and LUMO energies, and their difference (E\u003csub\u003egap\u003c/sub\u003e).\u003c/p\u003e\u003cp\u003eHardness (ƞ)[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e] reflects a molecule's resistance to electron distribution changes, which is calculated based on the energy difference between IP and EA [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e], while softness (S)[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e] indicates its ability to transfer electrons. Hardness and softness are defined by the following equations (Eq.\u0026nbsp;(1) and Eq.\u0026nbsp;(2)), respectively. Higher hardness reduces antioxidant activity, whereas greater softness enhances it [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. Furthermore, hard molecules, with a large energy gap (E\u003csub\u003egap\u003c/sub\u003e), exhibit low charge transfer ability and weak antioxidant activity. In contrast, soft molecules have a smaller E\u003csub\u003egap\u003c/sub\u003e, enabling efficient electron transfer and stronger radical scavenging capability [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eƞ = (IP ‒ EA) / 2 (1)\u003c/p\u003e\u003cp\u003eS\u0026thinsp;=\u0026thinsp;1 / (2 ƞ) (2)\u003c/p\u003e\u003cp\u003eElectronegativity (χ) [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e] is regarded as one of the most significant chemical descriptors for explaining the tendency of atoms to form molecular systems. It is calculated as the mean of the vertical ionization energy and the vertical electron affinity of a molecule (Eq.\u0026nbsp;(3)) [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. Consequently, the electronic chemical potential (\u0026micro;) [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e], formulated as the negative of electronegativity (Eq.\u0026nbsp;(4)), determines electron movement from high to low potential regions. Higher \u0026micro; values correlate with greater radical scavenging activity [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e].\u003c/p\u003e\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eΧ = (IP\u0026thinsp;+\u0026thinsp;EA)/2 (3)\u003c/h2\u003e\u003cp\u003e\u0026micro; = ‒ χ (4)\u003c/p\u003e\u003cp\u003eMoreover, the electrophilicity index (ω) [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e] quantifies the upper limit of electron transfer between donor and acceptor species (Eq.\u0026nbsp;(5)). Compounds with higher ω values exhibit greater electrophilicity and enhanced antioxidant activity [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eΩ = \u0026micro;\u003csup\u003e2\u003c/sup\u003e / (2 ƞ) (5)\u003c/p\u003e\u003c/div\u003e"},{"header":"Results and discussion","content":"\u003cp\u003eThe optimized structure of \u003cem\u003easpulvinone E\u003c/em\u003e is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. In accordance with the most stable molecular geometry obtained from conformational analysis, it has a fully planar structure (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Numerous potential reactions between \u003cem\u003easpulvinone E\u003c/em\u003e and free radicals are possible in a water-based environment. Elaborating on these reactions is key to understanding their antioxidant activity [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. In particular, reactions related to antioxidant activity can be grouped into two basic types of mechanisms: (i) hydrogen atom abstraction and (ii) radical addition (radical adduct formation, RAF) [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e] (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Hydrogen atom abstraction can occur according to three different pathways: direct hydrogen atom transfer (HAT), single-electron transfer-proton transfer (SET-PT), and sequential proton loss-electron transfer (SPLET) [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. All the above-mentioned mechanisms have been modeled in aqueous media.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eDue to its mild reactivity, the \u0026bull;OOH radical is regarded as a model free radical for assessing the antiradical activities of organic compounds [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. Studies on the radical scavenging ability of natural products against other common reactive oxygen species, such as \u0026bull;OH, are critical to provide useful information regarding their antioxidant activities. Therefore, the reactivity of \u003cem\u003easpulvinone E\u003c/em\u003e was also modeled against \u0026bull;OH radical following the main mechanisms in water: hydrogen atom transfer (HAT) and radical adduct formation (RAF) [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eBecause each hydroxyl (‒OH) of the molecule can show dissimilar activity in scavenging free radicals, H-atom transfer reactions between an \u0026bull;OH and \u0026bull;OOH species and hydroxyl groups at different positions were studied. To be more specific, we have considered radical addition to accessible C\u0026thinsp;=\u0026thinsp;C bond carbon atoms (C1, C2, C3), as well as H abstraction from hydroxyl groups (from positions H-1, H-2, and H-3) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\n\u003ch3\u003eHAT Mechanism\u003c/h3\u003e\n\u003cp\u003eThe reactivity of the \u0026bull;OOH and \u0026bull;OH radicals was evaluated through HAT mechanism and corresponding optimized structures for the transition states (TS) are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. For \u0026bull;OOH radical it was found that the activation Gibbs free energy of H-abstraction from position H-3 is 20.22 kJ mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), which is lower than those corresponding to positions H-1 (44.91 kJ mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and H-2 (39.68 kJ mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e). The same trend was observed in the results obtained from \u0026bull;OH radical; the activation Gibbs free energy of H-abstraction from position H-3 is 0.92 kJ mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, which is lower than those corresponding to positions H-1 (3.55 kJ mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and H-2 (7.26 kJ mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The H-3 hydroxyl group is certainly the most reactive site because the formed radical at this position can be stabilized strongly by a longer-range resonance between the two aromatic rings.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eEnergetics (kJ mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and kinetics (L mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) for hydrogen (H-1, H-2, and H-3) transfer reactions to HOO\u0026bull; and HO\u0026bull; (M06-2X/6\u0026ndash;31\u0026thinsp;+\u0026thinsp;G(d) level, 298.15 K, in water polarized implicit solvent medium).\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHOO\u0026bull;\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\varvec{\\Delta\\:}\\mathbf{G}}_{\\mathbf{r}\\mathbf{x}\\mathbf{n}}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\varvec{\\Delta\\:}\\mathbf{G}}^{\\ddagger}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003ek\u003csub\u003ewater\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eWigner\u003c/p\u003e\u003cp\u003eFactor\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eH‒1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e44.91\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.25E\u0026thinsp;+\u0026thinsp;07\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e5.99\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eH‒2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-5.10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e39.68\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e9.95E\u0026thinsp;+\u0026thinsp;07\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e5.78\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eH‒3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-38.40\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e20.22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.36E\u0026thinsp;+\u0026thinsp;11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e7.61\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e\u003cp\u003eHO\u0026bull;\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eH‒1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-129.46\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3.55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.57E\u0026thinsp;+\u0026thinsp;14\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e4.28\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eH‒2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-128.11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7.26\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e6.16E\u0026thinsp;+\u0026thinsp;13\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e7.48\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eH‒3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-170.80\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.92\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e4.09E\u0026thinsp;+\u0026thinsp;14\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3.85\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eFurthermore, radical stabilization energy (RSE) [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e] values of radical structures formed after the HAT mechanism are presented in Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e (Supporting Information). The formed radical at position 3 (H-3) exhibits the highest RSE value (137.68 kJ mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), indicating that this radical structure is more stable than other radicals formed after transferring H-1 and H-2 hydrogen atoms.\u003c/p\u003e\u003cp\u003eMarino et al. [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e] reported related to the antioxidant activity of gallic acid that the Gibbs free energy of activation for H-abstraction by \u0026bull;OOH radical from the phenolic -OH group in a water-based environment was approximately 50.07 kJ mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. In another research, Vo et al. [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e] worked on the antioxidant activity of syringic acid. They found that in an aqueous environment, the Gibbs free energy of H-abstraction from the phenolic -OH group by \u0026bull;OH radical is 25.96 kJ mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Our study has revealed that the activation energies of the HAT mechanism are lower than those reported in the literature. Consequently, within the framework of the HAT mechanism, these findings suggest that the \u003cem\u003easpulvinone E\u003c/em\u003e possesses higher reactivity and superior antioxidant properties relative to gallic acid and syringic acid.\u003c/p\u003e\n\u003ch3\u003eRAF Mechanism\u003c/h3\u003e\n\u003cp\u003eWithin the scope of this study, the radical adduct formation (RAF) process with \u0026bull;OOH and \u0026bull;OH addition at C1, C2, and C3 positions was investigated, and corresponding optimized structures for the transition states (TS) are presented in Fig.\u0026nbsp;3. Calculated Gibbs free energies are reported in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The Cartesian coordinates for all the RAF transition configurations can be found in Table S3 (Supporting Information section).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eEnergetics (kJ mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and kinetics (L mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) for HOO\u0026bull; and HO\u0026bull; addition reactions to C-1, C-2, and C-3 (M06-2X/6\u0026ndash;31\u0026thinsp;+\u0026thinsp;G(d) level, 298.15 K, in water polarized implicit solvent medium).\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHOO\u0026bull;\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\varvec{\\Delta\\:}\\mathbf{G}}_{\\mathbf{r}\\mathbf{x}\\mathbf{n}}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\varvec{\\Delta\\:}\\mathbf{G}}^{\\ddagger}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003ek\u003csub\u003ewater\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eC‒1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-67.33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e27.90\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.99E\u0026thinsp;+\u0026thinsp;09\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eC‒2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-57.39\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e24.07\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e9.35E\u0026thinsp;+\u0026thinsp;09\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eC‒3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-36.82\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e38.51\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.76E\u0026thinsp;+\u0026thinsp;07\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e\u003cp\u003eHO\u0026bull;\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eC‒1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-138.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4.08\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.20E\u0026thinsp;+\u0026thinsp;12\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eC‒2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-103.49\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e11.12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e7.01E\u0026thinsp;+\u0026thinsp;10\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eC‒3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-140.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e12.28\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e4.38E\u0026thinsp;+\u0026thinsp;10\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe transition states (TSs) for the addition path at C1 and C2 positions are earlier than at C3 position, for both reactions with \u0026bull;OOH and \u0026bull;OH radicals. This suggests that position C3 should be the least reactive site via RAF. In addition, all the TS for the \u0026bull;OH reactions are earlier than the corresponding ones involving \u0026bull;OOH, which is in agreement with the relative reactivity difference of these radicals.\u003c/p\u003e\u003cp\u003eCalculations on the HAT reaction mechanism kinetics revealed that the rate constants for \u0026bull;OOH radical reactions vary from 7 to 11 orders of magnitude. The fastest reaction occurs at the H-3 position, and the calculated rate coefficient is 3.36 \u0026times; 10\u003csup\u003e11\u003c/sup\u003e L mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Moreover, the more reactive \u0026bull;OH radical exhibits a remarkably diffusion-controlled reaction; the rate constants of all hydrogen atom transfer reactions are greater than 11 orders of magnitude.\u003c/p\u003e\u003cp\u003eAdditionally, calculations on the RAF mechanism kinetics (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) exhibited that the rate constants for \u0026bull;OOH radical reactions vary from 7 to 9 orders of magnitude. The slowest addition occurs at the C-3 position with the rate coefficient 2.76\u0026thinsp;+\u0026thinsp;10\u003csup\u003e7\u003c/sup\u003e L mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Attacking the other position shows relatively faster reactions; the rate coefficients are 1.99\u0026thinsp;+\u0026thinsp;10\u003csup\u003e9\u003c/sup\u003e and 9.35\u0026thinsp;+\u0026thinsp;10\u003csup\u003e9\u003c/sup\u003e L mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at C-1 and C-2, respectively. Moreover, the addition reaction of \u0026bull;OH radical is diffusion-controlled reaction rates at any accessible C\u0026thinsp;=\u0026thinsp;C double bond positions. We have considered that reactions take place through a typical complex two-step mechanism. The initial phase involves the generation of a pre-reactive complex in equilibrium with the reactants, followed by a second, irreversible stage leading to product formation [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e].\u003c/p\u003e\n\u003ch3\u003eSET-PT and SPLET Mechanisms\u003c/h3\u003e\n\u003cp\u003eThe SET-PT mechanism involves two primary reactions; the first reaction requires an adiabatic ionization potential (AIP) energy, which refers to the lowest amount of energy necessary to detach an electron from molecule or atom in its ground state, without any excess vibrational or rotational excitation. The second reaction is characterized by proton dissociation energy (PDE) of cationic antioxidant radical (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eFurthermore, the SPLET mechanism's first step entails dissociating an antioxidant's phenolic-OH group into an anion and a proton, with proton affinity (PA) quantifying this process. The next step entails the anion reacting with a free radical, which results in the formation of a neutral species and a phenolic antioxidant radical. Throughout this stage, an electron transfer occurs from the anion toward the free radical, which is characterized by electron transfer enthalpy (ETE) [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e, \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e] (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eIn the context of the SET-PT and SPLET mechanisms, as mentioned above, AIP and PA represent the initial steps, serving as crucial determinants. Consequently, BDE, AIP, and PA numerical values are frequently employed to identify the thermodynamically favored reaction pathway. Additionally, computed BDE values may be useful in determining if the HAT mechanism is kinetically preferred; the more likely the associated mechanism, the lower the energy of this descriptor [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eIn molecules exhibiting high AIP values, electron donation is significantly challenging. The studied molecule has a PA value exceeding its AIP, indicating that the SET-PT mechanism is more likely than the SPLET pathway. However, calculations show that the values obtained for BDE are considerably less than those determined for AIP and PA (Table S2). Therefore, from the energetic point of view, HAT is the preferred reaction path in the water solvent medium.\u003c/p\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003eAnalysis with Descriptors\u003c/h2\u003e\u003cp\u003eThe antioxidant property of \u003cem\u003easpulvinone E\u003c/em\u003e was also evaluated based on various quantum chemical descriptors and compared with the findings in the literature (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e and Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). The main parameters used in this evaluation include ionization potential (IP), electron affinity (EA), chemical hardness (η), softness (S), electronegativity (χ), chemical potential (\u0026micro;), electrophilic index (ω), and frontier molecular orbital energies (HOMO, LUMO, and their energy difference E\u003csub\u003egap\u003c/sub\u003e).\u003c/p\u003e\u003cp\u003eA higher IP signifies a reduced tendency for electron donation. Conversely, molecules exhibiting higher EA values are more prone to electron gain than those with lower EA [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. Compared to the data reported in the literature (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e), \u003cem\u003easpulvinone E\u003c/em\u003e exhibits a lower IP value than apigenin [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] and aloe-emodin[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e] antioxidants, shows electron-donating capability towards radical species, and indicates its higher antioxidant activity. On the contrary, resveratrol [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e] has the lowest value compared to \u003cem\u003easpulvinone E\u003c/em\u003e, apigenin, and aloe-emodin. The highest electron affinity was found in aloe-emodin [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e], indicates the highest capacity to extract an electron from a radical species. Furthermore, the greater antioxidant property of \u003cem\u003easpulvinone E\u003c/em\u003e compared to apigenin and resveratrol is evident from the fact that its EA value is higher than that of apigenin [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] and resveratrol [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eIE and EA parameters (kJ mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) of \u003cem\u003easpulvinone E\u003c/em\u003e compared with the data presented in the literature (in PCM medium with implicit water).\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eThis Study\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eApigenin [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eAloe-emodin [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eQuercetin [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eResveratrol [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eM062X/6\u0026ndash;31\u0026thinsp;+\u0026thinsp;G*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eB3LYP/6-311G(d,p)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eB3LYP/6\u0026ndash;311\u0026thinsp;+\u0026thinsp;+\u0026thinsp;G**\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eB3LYP/6-311G(d,p)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eB3LYP/6-311G(d,p)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eIP\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e586.88\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e593.88\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e637.80\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e524.92\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e520.11\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eEA\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e250.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e190.04\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e300.08\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e230.84\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e203.18\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe computed parameters based on descriptors and frontier orbital theory analysis are presented in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. When evaluated in terms of chemical hardness and softness, \u003cem\u003easpulvinone E\u003c/em\u003e exhibits low hardness (η\u0026thinsp;\u0026asymp;\u0026thinsp;1.74 eV) and high softness (S\u0026thinsp;\u0026asymp;\u0026thinsp;0.29 1/eV) like aloe-emodin, indicating that these molecules may be more reactive and therefore more potent antioxidant candidates than apigenin and quercetin. Electronegativity (χ) and chemical potential (\u0026micro;) parameters are used to determine molecule\u0026rsquo;s electron-withdrawing and electron-donating tendencies. In terms of antioxidant effect, compounds with high electron-donating tendencies are preferred. In this context, quercetin has the lowest electronegativity and the least negative chemical potential, while \u003cem\u003easpulvinone E\u003c/em\u003e has a higher electronegativity compared to quercetin and apigenin, which means that it will exhibit a relatively weaker profile in terms of electron donation tendency.\u003c/p\u003e\u003cp\u003eWhen the electrophilic indices (ω) are evaluated, it is seen that aloe-emodin has the highest value (6.75 eV) indicating that it has a very high capacity to capture nucleophilic free radicals. Therefore, it shows less reactivity when reacting with electrophilic radicals such as HO\u0026bull; and CH\u003csub\u003e3\u003c/sub\u003eO\u0026bull;. Similarly, \u003cem\u003easpulvinone E\u003c/em\u003e has a relatively high value (5.51 eV), suggesting the molecule can act as an electron acceptor.\u003c/p\u003e\u003cp\u003eFrontier orbital energies (HOMO, LUMO) and the energy difference between them (E\u003csub\u003egap\u003c/sub\u003e) can be involved in determining the kinetic stability and reactivity of molecules. High HOMO energy represents the electron-donating capacity of the molecule, while a low HOMO-LUMO gap (Egap) means higher chemical reactivity. In this respect, quercetin and aloe-emodin have the lowest Egap values ​​and stand out as the most reactive and free radical scavenging compounds. In contrast, \u003cem\u003easpulvinone E\u003c/em\u003e has the lowest HOMO and highest Egap values, making it the least reactive molecule with the lowest electron-donating capacity. This result is also consistent with the relatively high electrophilic index (ω) value of \u003cem\u003easpulvinone E\u003c/em\u003e.\u003c/p\u003e\u003cp\u003eWhen a general evaluation is made, aloe-emodin has a more balanced and powerful antioxidant profile in terms of studied descriptors. It can be said that it shows high free radical scavenging capacity with low hardness and Egap. On the other hand, \u003cem\u003easpulvinone E\u003c/em\u003e offers a strong antioxidant potential in some aspects (hardness and softness). However, its overall reactivity can be considered as limited due to its high HOMO-LUMO gap and low HOMO energy. This suggests that it may be reluctant to donate electrons and have a more kinetically stable structure. Apigenin and quercetin, on the other hand, show lower antioxidant activity with their lower electrophilicity and harder structures; however, quercetin is in an advantageous position in terms of HOMO level and Egap, and is expected to exhibit a remarkable performance, especially in electron donation-based mechanisms.\u003c/p\u003e\u003cp\u003eAs a result, in light of the descriptors studied, it can be thought that \u003cem\u003easpulvinone E\u003c/em\u003e, despite its potential, may exhibit a limited antioxidant capacity due to its specific electronic properties; however, possessing relatively lower hardness and higher softness strongly enhances its antioxidant capacity.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eParameters (eV) computed to determine and describe the mechanism involved in free radical scavenging compared with the data presented in the literature.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eThis Study\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eApigenin [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eAloe-emodin [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eQuercetin [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eƞ\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.74\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3.30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.74\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3.23\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eS\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.29\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.28\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.15\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eχ\u003csub\u003ex\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4.34\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4.19\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e4.85\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3.99\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u0026micro;\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-4.34\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-4.19\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-4.85\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-3.99\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eω\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e5.51\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.66\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e6.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e2.47\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHOMO\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-6.94\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-6.15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-6.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-5.69\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLUMO\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-1.69\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-1.98\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-3.11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e-2.30\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eE\u003csub\u003egap\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e5.26\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4.17\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.48\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3.38\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eIt should be emphasized that Apigenin, Resveratrol, and Quercetin, owing to their pronounced antioxidant efficacy, have undergone successful commercial development. These compounds exhibit sustained market presence and demonstrate medically relevant applications increasingly supported by scientific research [\u003cspan additionalcitationids=\"CR42\" citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e].\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eFrontier Orbital Theory Analysis\u003c/h3\u003e\n\u003cp\u003eTo investigate the correlation between electron delocalization and the reactivity of the \u003cem\u003easpulvinone E\u003c/em\u003e structure, we generate density plots of the HOMO and LUMO compositions (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e6\u003c/span\u003e). Plotting HOMO orbitals can also be utilized to find locations with a high distribution of HOMO electronic density. In biological systems, electrophilic free radical attack preferentially targets the regions of the molecule where the HOMO electron density is highest[\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e6\u003c/span\u003e, in the \u003cem\u003easpulvinone E\u003c/em\u003e structure, HOMO and LUMO are largely delocalized throughout the molecule except O3 atom for HOMO and C1, C2, C15, C16, and O3 atoms for LUMO. The presence of HOMO density facilitates the formation of sites sensitive to interactions with free radicals, thereby enhancing the antioxidant properties of butenolide. Analysis of the HOMO orbital in the non-radical form of \u003cem\u003easpulvinone E\u003c/em\u003e reveals that electron density is predominantly localized on the phenyl and furanone rings. At the same time, it is mainly located on the furanone ring for LUMO. This finding emphasizes the importance of the unsaturated carbon bonds in the furanone side for the radical attack with the RAF mechanism and the critical role of hydroxyl groups in scavenging free radicals by the HAT mechanism [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThe antioxidant activity of \u003cem\u003easpulvinone E\u003c/em\u003e was thoroughly examined through quantum chemical approach. Thermodynamically and kinetically revealed the H-3 hydroxyl as the most reactive site for HAT, with significantly lower activation Gibbs free energy values for hydrogen abstraction by \u0026bull;OOH (20.22 kJ mol⁻\u0026sup1;) and \u0026bull;OH radicals (0.92 kJ mol⁻\u0026sup1;), compared to H-1 and H-2 positions. The radical formed at H-3 showed the highest stabilization energy (RSE\u0026thinsp;=\u0026thinsp;137.68 kJ mol⁻\u0026sup1;), indicating superior stability via extended conjugation throughout aromatic rings. Kinetic studies showed that HAT at H-3 yielded the highest reaction rate for \u0026bull;OOH radicals (k\u0026thinsp;=\u0026thinsp;3.36 \u0026times; 10\u0026sup1;\u0026sup1; L mol⁻\u0026sup1; s⁻\u0026sup1;), while all \u0026bull;OH-mediated HAT processes were diffusion-controlled with rate constants exceeding 10\u0026sup1;\u0026sup1; L mol⁻\u0026sup1; s⁻\u0026sup1;. RAF analysis further confirmed the positional influence on reactivity: C1 addition by \u0026bull;OOH was the most favorable (ΔG = \u0026minus;\u0026thinsp;67.33 kJ mol⁻\u0026sup1;), while \u0026bull;OH radical addition at C3 yielded the highest exergonicity (ΔG = \u0026minus;\u0026thinsp;140.25 kJ mol⁻\u0026sup1;).\u003c/p\u003e\u003cp\u003eThe molecule\u0026rsquo;s moderate ionization potential and elevated electron affinity suggest promising free radical interaction capacity, making it a viable electron donor. Furthermore, electronic structure descriptors indicate low hardness (η\u0026thinsp;\u0026asymp;\u0026thinsp;1.74 eV), high softness (S\u0026thinsp;\u0026asymp;\u0026thinsp;0.29 1/eV), and moderate electrophilicity (ω\u0026thinsp;=\u0026thinsp;5.51 eV), positioning the molecule as a responsive electron donor with favorable radical-scavenging attributes. The HOMO density distribution predominantly over the phenyl and furanone moieties suggests targeted radical scavenging at these sites, a feature likely enhanced by the hydroxyl group presence.\u003c/p\u003e\u003cp\u003eCollectively, these findings support \u003cem\u003easpulvinone E\u003c/em\u003e\u0026rsquo;s potential as a selective and stable antioxidant. While its reactivity may be mechanism-dependent, particularly favoring HAT, the compound\u0026rsquo;s distinctive electronic attributes warrant further biological assessment and potential therapeutic development.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthor contribution\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eB. G. N. contributed to the investigation, calculations, data curation, writing the original draft, formal analysis, and visualization. I. D. was involved in methodology, investigation, calculations, validation, resources, supervision, and writing review \u0026amp; editing. The authors were both involved in reviewing.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eCorresponding authors: Belma Gjergjizi Nallbani and Isa Degirmenci\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgment\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors are thankful to TUBITAK ULAKBIM and Ondokuz Mayıs University; the calculations reported in this research were partially performed at TUBITAK ULAKBIM, High Performance and Grid Computing Center (TRUBA resources), and Ondokuz Mayıs University.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThere is no conflict of interest for this study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical Approval\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis declaration is \u0026ldquo;not applicable.\u0026rdquo;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis declaration is \u0026ldquo;not applicable.\u0026rdquo; This study was not supported by any funding.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll optimized geometries and relevant data generated and analyzed throughout this study are included in the manuscript and its supplementary information.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eRahaman MM, Hossain R, Herrera-Bravo J, Islam MT, Atolani O, Adeyemi OS, Owolodun OA, Kambizi L, Daştan SD, Calina D, Sharifi‐Rad J (2023) Natural antioxidants from some fruits, seeds, foods, natural products, and associated health benefits: An update. Food Sci Nutr 11:1657\u0026ndash;1670. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1002/fsn3.3217\u003c/span\u003e\u003cspan address=\"10.1002/fsn3.3217\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eXu X, Liu A, Hu S, Ares I, Mart\u0026iacute;nez-Larra\u0026ntilde;aga M-R, Wang X, Mart\u0026iacute;nez M, Anad\u0026oacute;n A, Mart\u0026iacute;nez M-A (2021) Synthetic phenolic antioxidants: Metabolism, hazards and mechanism of action. Food Chem 353:129488. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.foodchem.2021.129488\u003c/span\u003e\u003cspan address=\"10.1016/j.foodchem.2021.129488\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eChaudhary P, Janmeda P, Docea AO, Yeskaliyeva B, Abdull Razis AF, Modu B, Calina D, Sharifi-Rad J (2023) Oxidative stress, free radicals and antioxidants: potential crosstalk in the pathophysiology of human diseases. Front Chem 11. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3389/fchem.2023.1158198\u003c/span\u003e\u003cspan address=\"10.3389/fchem.2023.1158198\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eParcheta M, Świsłocka R, Orzechowska S, Akimowicz M, Choińska R, Lewandowski W (2021) Recent Developments in Effective Antioxidants: The Structure and Antioxidant Properties. Materials 14:1984. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3390/ma14081984\u003c/span\u003e\u003cspan address=\"10.3390/ma14081984\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCipolletti M, Solar Fernandez V, Montalesi E, Marino M, Fiocchetti M (2018) Beyond the Antioxidant Activity of Dietary Polyphenols in Cancer: the Modulation of Estrogen Receptors (ERs) Signaling. Int J Mol Sci 19:2624. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3390/ijms19092624\u003c/span\u003e\u003cspan address=\"10.3390/ijms19092624\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGulcin İ (2020) Antioxidants and antioxidant methods: an updated overview. Arch Toxicol 94:651\u0026ndash;715. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s00204-020-02689-3\u003c/span\u003e\u003cspan address=\"10.1007/s00204-020-02689-3\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLiao G, Wu P, Xue J, Liu L, Li H, Wei X (2018) Asperimides A\u0026ndash;D, anti-inflammatory aromatic butenolides from a tropical endophytic fungus Aspergillus terreus. Fitoterapia 131:50\u0026ndash;54. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.fitote.2018.10.011\u003c/span\u003e\u003cspan address=\"10.1016/j.fitote.2018.10.011\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGuo F, Li Z, Xu X, Wang K, Shao M, Zhao F, Wang H, Hua H, Pei Y, Bai J (2016) Butenolide derivatives from the plant endophytic fungus Aspergillus terreus. Fitoterapia 113:44\u0026ndash;50. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.fitote.2016.06.014\u003c/span\u003e\u003cspan address=\"10.1016/j.fitote.2016.06.014\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePeng Q, Chen W, Lin X, Xiao J, Liu Y, Zhou X (2022) Butenolides from the Coral-Derived Fungus Aspergillius terreus SCSIO41404. Mar Drugs 20:212. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3390/md20030212\u003c/span\u003e\u003cspan address=\"10.3390/md20030212\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eElhady SS, Alshobaki NM, Elfaky MA, Koshak AE, Alharbi M, Abdelhameed RFA, Darwish KM (2023) Deciphering Molecular Aspects of Potential α-Glucosidase Inhibitors within Aspergillus terreus: A Computational Odyssey of Molecular Docking-Coupled Dynamics Simulations and Pharmacokinetic Profiling. Metabolites 13:942. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3390/metabo13080942\u003c/span\u003e\u003cspan address=\"10.3390/metabo13080942\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHaritakun R, Rachtawee P, Chanthaket R, Boonyuen N, Isaka M (2010) Butyrolactones from the Fungus Aspergillus terreus BCC 4651. Chem Pharm Bull (Tokyo) 58:1545\u0026ndash;1548. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1248/cpb.58.1545\u003c/span\u003e\u003cspan address=\"10.1248/cpb.58.1545\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eZhang YY, Zhang Y, Yao Y-B, Lei X-L, Qian Z-J (2018) Butyrolactone-I from Coral-Derived Fungus Aspergillus terreus Attenuates Neuro-Inflammatory Response via Suppression of NF-κB Pathway in BV-2 Cells. Mar Drugs 16:202. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3390/md16060202\u003c/span\u003e\u003cspan address=\"10.3390/md16060202\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWu Y, Chen Y, Huang X, Pan Y, Liu Z, Yan T, Cao W, She Z (2018) α-Glucosidase Inhibitors: Diphenyl Ethers and Phenolic Bisabolane Sesquiterpenoids from the Mangrove Endophytic Fungus Aspergillus flavus QQSG-3. Mar Drugs 16. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3390/md16090307\u003c/span\u003e\u003cspan address=\"10.3390/md16090307\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSun Y, Liu J, Li L, Gong C, Wang S, Yang F, Hua H, Lin H (2018) New butenolide derivatives from the marine sponge-derived fungus Aspergillus terreus. Bioorg Med Chem Lett 28:315\u0026ndash;318. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.bmcl.2017.12.049\u003c/span\u003e\u003cspan address=\"10.1016/j.bmcl.2017.12.049\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSadasivam K, Kumaresan R (2011) A comparative DFT study on the antioxidant activity of apigenin and scutellarein flavonoid compounds. Mol Phys 109:839\u0026ndash;852. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1080/00268976.2011.556576\u003c/span\u003e\u003cspan address=\"10.1080/00268976.2011.556576\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eVo QV, Tam NM, Bay M, Van, Mechler A (2020) The radical scavenging activity of natural ramalin: A mechanistic and kinetic study. Chem Phys Lett 739:137004. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.cplett.2019.137004\u003c/span\u003e\u003cspan address=\"10.1016/j.cplett.2019.137004\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eVo QV, Gon T, Van BM, Van, Mechler A (2019) Antioxidant Activities of Monosubstituted Indolinonic Hydroxylamines: A Thermodynamic and Kinetic Study. J Phys Chem B 123:10672\u0026ndash;10679. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1021/acs.jpcb.9b08912\u003c/span\u003e\u003cspan address=\"10.1021/acs.jpcb.9b08912\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGalano A, Ra\u0026uacute;l Alvarez-Idaboy J (2019) Computational strategies for predicting free radical scavengers\u0026rsquo; protection against oxidative stress: Where are we and what might follow? Int J Quantum Chem 119. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1002/qua.25665\u003c/span\u003e\u003cspan address=\"10.1002/qua.25665\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBoulebd H (2020) Theoretical insights into the antioxidant activity of moracin T. Free Radic Res 54:221\u0026ndash;230. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1080/10715762.2020.1747616\u003c/span\u003e\u003cspan address=\"10.1080/10715762.2020.1747616\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eIuga C, Alvarez-Idaboy JR, Russo N (2012) Antioxidant Activity of trans -Resveratrol toward Hydroxyl and Hydroperoxyl Radicals: A Quantum Chemical and Computational Kinetics Study. J Org Chem 77:3868\u0026ndash;3877. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1021/jo3002134\u003c/span\u003e\u003cspan address=\"10.1021/jo3002134\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMarino T, Galano A, Russo N (2014) Radical Scavenging Ability of Gallic Acid toward OH and OOH Radicals. Reaction Mechanism and Rate Constants from the Density Functional Theory. J Phys Chem B 118:10380\u0026ndash;10389. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1021/jp505589b\u003c/span\u003e\u003cspan address=\"10.1021/jp505589b\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBay M, Van, Nam PC, Quang DT, Mechler A, Hien NK, Hoa NT, Vo QV (2020) Theoretical Study on the Antioxidant Activity of Natural Depsidones. ACS Omega 5:7895\u0026ndash;7902. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1021/acsomega.9b04179\u003c/span\u003e\u003cspan address=\"10.1021/acsomega.9b04179\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eVo QV, Bay M, Van, Nam PC, Quang DT, Flavel M, Hoa NT, Mechler A (2020) Theoretical and Experimental Studies of the Antioxidant and Antinitrosant Activity of Syringic Acid. J Org Chem 85:15514\u0026ndash;15520. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1021/acs.joc.0c02258\u003c/span\u003e\u003cspan address=\"10.1021/acs.joc.0c02258\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFrisch MJ (2016) Gaussian 16, Revision B.01. Gaussian. Inc., Wallingford CT\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMarenich AV, Cramer CJ, Truhlar DG (2009) Universal Solvation Model Based on Solute Electron Density and on a Continuum Model of the Solvent Defined by the Bulk Dielectric Constant and Atomic Surface Tensions. J Phys Chem B 113:6378\u0026ndash;6396. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1021/jp810292n\u003c/span\u003e\u003cspan address=\"10.1021/jp810292n\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eChandrakumar KRS, Pal S (2002) The Concept of Density Functional Theory Based Descriptors and its Relation with the Reactivity of Molecular Systems: A Semi-Quantitative Study. Int J Mol Sci 3:324\u0026ndash;337. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3390/i3040324\u003c/span\u003e\u003cspan address=\"10.3390/i3040324\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMarenich AV, Cramer CJ, Truhlar DG (2009) Universal Solvation Model Based on Solute Electron Density and on a Continuum Model of the Solvent Defined by the Bulk Dielectric Constant and Atomic Surface Tensions. J Phys Chem B 113:6378\u0026ndash;6396. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1021/jp810292n\u003c/span\u003e\u003cspan address=\"10.1021/jp810292n\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eReza Nazifi SM, Asgharshamsi MH, Dehkordi MM, Zborowski KK (2019) Antioxidant properties of Aloe vera components: a DFT theoretical evaluation. Free Radic Res 53:922\u0026ndash;931. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1080/10715762.2019.1648798\u003c/span\u003e\u003cspan address=\"10.1080/10715762.2019.1648798\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFoti MC, Daquino C, Geraci C (2004) Electron-Transfer Reaction of Cinnamic Acids and Their Methyl Esters with the DPPH\u0026bull; Radical in Alcoholic Solutions. J Org Chem 69:2309\u0026ndash;2314. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1021/jo035758q\u003c/span\u003e\u003cspan address=\"10.1021/jo035758q\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLu L, Qiang M, Li F, Zhang H, Zhang S (2014) Theoretical investigation on the antioxidative activity of anthocyanidins: A DFT/B3LYP study. Dyes Pigm 103:175\u0026ndash;182. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.dyepig.2013.12.015\u003c/span\u003e\u003cspan address=\"10.1016/j.dyepig.2013.12.015\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMurphy LR, Meek TL, Allred AL, Allen LC (2000) Evaluation and Test of Pauling\u0026rsquo;s Electronegativity Scale. J Phys Chem A 104:5867\u0026ndash;5871. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1021/jp000288e\u003c/span\u003e\u003cspan address=\"10.1021/jp000288e\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMulliken RS (1934) A New Electroaffinity Scale; Together with Data on Valence States and on Valence Ionization Potentials and Electron Affinities. J Chem Phys 2:782\u0026ndash;793. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1063/1.1749394\u003c/span\u003e\u003cspan address=\"10.1063/1.1749394\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAkhtari K, Hassanzadeh K, Fakhraei B, Fakhraei N, Hassanzadeh H, Zarei SA (2013) A density functional theory study of the reactivity descriptors and antioxidant behavior of Crocin. Comput Theor Chem 1013:123\u0026ndash;129. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.comptc.2013.03.015\u003c/span\u003e\u003cspan address=\"10.1016/j.comptc.2013.03.015\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSiddeeg A, AlKehayez NM, Abu-Hiamed HA, Al-Sanea EA, AL-Farga AM (2021) Mode of action and determination of antioxidant activity in the dietary sources: An overview. Saudi J Biol Sci 28:1633\u0026ndash;1644. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.sjbs.2020.11.064\u003c/span\u003e\u003cspan address=\"10.1016/j.sjbs.2020.11.064\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePerez-Gonzalez A, Mu\u0026ntilde;oz-Rugeles L, Alvarez-Idaboy JR (2014) Tryptophan: antioxidant or target of oxidative stress? A quantum chemistry elucidation. RSC Adv 4:56128\u0026ndash;56131. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1039/C4RA11635F\u003c/span\u003e\u003cspan address=\"10.1039/C4RA11635F\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eNgoc TD, Thi Ha MV, Le TN, Thi HV, Anh Nguyen T, Van, Mechler A, Hoa NT, Vo QV (2022) A Potent Antioxidant Sesquiterpene, Abelsaginol, from Abelmoschus sagittifolius: Experimental and Theoretical Insights. ACS Omega 7:24004\u0026ndash;24011. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1021/acsomega.2c02974\u003c/span\u003e\u003cspan address=\"10.1021/acsomega.2c02974\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHioe J, Zipse H (2010) Radical stability and its role in synthesis and catalysis. Org Biomol Chem 8:3609. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1039/c004166a\u003c/span\u003e\u003cspan address=\"10.1039/c004166a\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWang A, Lu Y, Du X, Shi P, Zhang H (2018) A theoretical study on the antioxidant activity of Uralenol and Neouralenol scavenging two radicals. Struct Chem 29:1067\u0026ndash;1075. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s11224-018-1090-8\u003c/span\u003e\u003cspan address=\"10.1007/s11224-018-1090-8\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePryor WA (1988) Why is the hydroxyl radical the only radical that commonly adds to DNA? Hypothesis: It has a rare combination of high electrophilicity, high thermochemical reactivity, and a mode of production that can occur near DNA. Free Radic Biol Med 4:219\u0026ndash;223. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/0891-5849(88)90043-3\u003c/span\u003e\u003cspan address=\"10.1016/0891-5849(88)90043-3\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePei L (2023) Theoretical Study on Methylated Resveratrol Analogues towards the Antioxidant Activity and Mechanisms: Understanding the Structure\u0026ndash;Activity Relationship. Russ J Phys Chem A 97:1121\u0026ndash;1127. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1134/S0036024423060171\u003c/span\u003e\u003cspan address=\"10.1134/S0036024423060171\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGaliniak S, Aebisher D, Bartusik-Aebisher D (2019) Health benefits of resveratrol administration. Acta Biochim Pol. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.18388/abp.2018_2749\u003c/span\u003e\u003cspan address=\"10.18388/abp.2018_2749\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSalehi B, Venditti A, Sharifi-Rad M, Kręgiel D, Sharifi-Rad J, Durazzo A, Lucarini M, Santini A, Souto EB, Novellino E, Antolak H, Azzini E, Setzer WN, Martins N (2019) The Therapeutic Potential of Apigenin. Int J Mol Sci 20:1305. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3390/ijms20061305\u003c/span\u003e\u003cspan address=\"10.3390/ijms20061305\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eYang D, Wang T, Long M, Li P (2020) Quercetin: Its Main Pharmacological Activity and Potential Application in Clinical Medicine. Oxid Med Cell Longev 2020:1\u0026ndash;13. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1155/2020/8825387\u003c/span\u003e\u003cspan address=\"10.1155/2020/8825387\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\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":"structural-chemistry","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"stuc","sideBox":"Learn more about [Structural Chemistry](https://www.springer.com/journal/11224)","snPcode":"11224","submissionUrl":"https://submission.nature.com/new-submission/11224/3","title":"Structural Chemistry","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"butenolide, aspulvinone E, antioxidant activity, theoretical calculations, M06-2X","lastPublishedDoi":"10.21203/rs.3.rs-7678529/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7678529/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn this study, the antioxidant mechanisms of \u003cem\u003easpulvinone E\u003c/em\u003e were systematically examined via quantum chemical calculations. Thermodynamic and kinetic analyses identified the H-3 hydroxyl group as the most reactive site for hydrogen atom transfer (HAT), exhibiting the lowest Gibbs free energy values for abstraction by \u0026bull;OOH and \u0026bull;OH radicals. Radical adduct formation (RAF) studies confirmed site-specific reactivity, favoring C1 addition by \u0026bull;OOH and C3 addition by \u0026bull;OH. Electronic properties\u0026mdash;including moderate ionization potential, high electron affinity, and favorable softness and electrophilicity parameters\u0026mdash;position the molecule as a responsive electron donor. HOMO distribution localized over phenyl and furanone moieties highlights targeted radical scavenging enhanced by hydroxyl functionalization. Overall, the combined thermodynamic, kinetic, and electronic profiles suggest that \u003cem\u003easpulvinone E\u003c/em\u003e possesses site-specific reactivity and enhanced stability, making it a promising candidate for antioxidant applications and further biological evaluation.\u003c/p\u003e","manuscriptTitle":"Computational Study: Antioxidant Activity of Aspulvinone E Toward Hydroperoxyl and Hydroxyl Radicals","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-10-16 11:06:32","doi":"10.21203/rs.3.rs-7678529/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-10-18T01:23:58+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-16T08:36:12+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-13T14:21:50+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-08T14:27:12+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"241923424425771850345481146673311056445","date":"2025-10-04T09:25:14+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"183946563323302248476775189030435052506","date":"2025-10-04T03:38:51+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"155670874897586458710147263506563020721","date":"2025-10-04T02:52:14+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-10-03T15:49:22+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-10-01T06:20:07+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-09-30T07:40:04+00:00","index":"","fulltext":""},{"type":"submitted","content":"Structural Chemistry","date":"2025-09-22T10:41:22+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"structural-chemistry","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"stuc","sideBox":"Learn more about [Structural Chemistry](https://www.springer.com/journal/11224)","snPcode":"11224","submissionUrl":"https://submission.nature.com/new-submission/11224/3","title":"Structural Chemistry","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"c905fd4b-230d-4c6d-8c91-ed6505be54ad","owner":[],"postedDate":"October 16th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-03-02T16:02:06+00:00","versionOfRecord":{"articleIdentity":"rs-7678529","link":"https://doi.org/10.1007/s11224-026-02746-0","journal":{"identity":"structural-chemistry","isVorOnly":false,"title":"Structural Chemistry"},"publishedOn":"2026-02-28 15:58:51","publishedOnDateReadable":"February 28th, 2026"},"versionCreatedAt":"2025-10-16 11:06:32","video":"","vorDoi":"10.1007/s11224-026-02746-0","vorDoiUrl":"https://doi.org/10.1007/s11224-026-02746-0","workflowStages":[]},"version":"v1","identity":"rs-7678529","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7678529","identity":"rs-7678529","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}