Density functional theory study of the structure-antioxidant activity of polyphenolic deoxybenzoins

In silico study on antidiabetic and antioxidant activity of bioactive compounds in Ficus carica L

Hyperglycemia is one of the diagnostic issues in diabetes mellitus and is considered as a complex metabolic condition. It has been one of the most prevalent illnesses of the twenty-first century and still rising at an alarming rate across the globe and expected to impact 693 million individuals by 2045. Therefore, it is mandatory to develop more effective and safer treatments to manage diabetes. One of the ways to manage hyperglycemia is through inhibiting carbohydrate digestion and thereby lowering the glucose formation in the human body. The enzyme salivary amylase and pancreatic amylase is responsible for cleaving α-1,4-glucoside bond. Amylase inhibitors can lower blood glucose in diabetics by slowing digestion. Ficus carica is commonly known for its medicinal properties due to its various phytochemicals. In the present study, 10 phytochemicals present in F. carica compounds named, β-carotene, lutein, cyanidin-3-glucoside, gallic acid, luteolin, catechin, kaempferol, vanillic acid, peonidin-3-glucoside, and quercetin hydrate were taken to study their inhibition potential against pancreatic amylase and salivary amylase through molecular docking and molecular dynamics simulations. Further, density functional theory calculations are used to investigate the delocalization of electron density on the molecule as well as study ADME properties of the molecules take. A QSAR model has been developed using the binding energy obtained using molecular docking and thermodynamic parameters from DFT calculations.Communicated by Ramaswamy H. Sarma.

Recent advances in computational prediction of molecular properties in food chemistry

The combination of food chemistry and computational simulation has brought many impacts to food research, moving from experimental chemistry to computer chemistry. This paper will systematically review in detail the important role played by computational simulations in the development of the molecular structure of food, mainly from the atomic, molecular, and multicomponent dimension. It will also discuss how different computational chemistry models can be constructed and analyzed to obtain reliable conclusions. From the calculation principle to case analysis, this paper focuses on the selection and application of quantum mechanics, molecular mechanics and coarse-grained molecular dynamics in food chemistry research. Finally, experiments and computations of food chemistry are compared and summarized to obtain the best balance between them. The above review and outlook will provide an important reference for the intersection of food chemistry and computational chemistry, and is expected to provide innovative thinking for structural research in food chemistry.

Polyphenols: Secondary Metabolites with a Biological Impression

Polyphenols are natural compounds which are plant-based bioactive molecules, and have been the subject of growing interest in recent years. Characterized by multiple varieties, polyphenols are mostly found in fruits and vegetables. Currently, many diseases are waiting for a cure or a solution to reduce their symptoms. However, drug or other chemical strategies have limitations for using a treatment agent or still detection tool of many diseases, and thus researchers still need to investigate preventive or improving treatment. Therefore, it is of interest to elucidate polyphenols, their bioactivity effects, supplementation, and consumption. The disadvantage of polyphenols is that they have a limited bioavailability, although they have multiple beneficial outcomes with their bioactive roles. In this context, several different strategies have been developed to improve bioavailability, particularly liposomal and nanoparticles. As nutrition is one of the most important factors in improving health, the inclusion of plant-based molecules in the daily diet is significant and continues to be enthusiastically researched. Nutrition, which is important for individuals of all ages, is the key to the bioactivity of polyphenols.

Synthesis, Cytotoxicity and Antioxidant Activity Evaluation of Some Thiazolyl-Catechol Compounds

A series of thiazolyl-catechol compounds with antioxidant and cytotoxic activities were synthesized by a Hantzsch heterocyclization, using diverse thioamides as the thiocarbonyl component and 4-chloroacetyl-catechol as haloketone. These compounds were characterized by MS, IR spectroscopy, and NMR. Their antioxidant potential was evaluated by antiradical, electron transfer, and ferrous ion chelation assays using ascorbic acid, Trolox, and EDTA-Na2 as references. The cytotoxicity of the synthesized compounds was evaluated on two different cell types, normal human foreskin fibroblasts (BJ) and human pulmonary malignant cells (A549), using gefitinib as a reference anticancer drug. The results obtained from the tests highlighted compounds 3g and 3h with significant antioxidant activities. The highest cytotoxic potency against A549 cells was exhibited by compounds 3i and 3j, while compound 3g demonstrated exceptional selectivity on malignant cells compared to gefitinib. These promising results encourage further investigation into targeted modifications on position 2 of the thiazole ring, in order to develop novel therapeutic agents.

Characterization, DFT study and evaluation of antioxidant potentials of mycosporine-like amino acids (MAAs) in the cyanobacterium Anabaenopsis circularis HKAR-22

The physiological parameters such as growth, Chl a content, and photosynthetic performance of the experimental cyanobacterium Anabaenopsis circularis HKAR-22 were estimated to evaluate the cumulative effects of photosynthetically active radiation (PAR) and ultraviolet (UV) radiation. Maximum induction of UV-screening molecules, MAAs, was observed under the treatment condition of PAR + UV-A + UV-B (PAB) radiations. UV/VIS absorption spectroscopy and HPLC-PDA detection primarily confirmed the presence of MAA-shinorine (SN) having absorption maxima (λmax) at 332.3 nm and retention time (RT) of 1.47 min. For further validation of the presence of SN, HRMS, FTIR and NMR were utilized. UV-stress elevated the in vivo ROS scavenging and in vitro enzymatic antioxidant capabilities. SN exhibited substantial and concentration-dependent antioxidant capabilities which was determined utilizing 2,2-diphenyl-1-picryl-hydrazyl (DPPH), 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonate (ABTS), ferric reducing power (FRAP) and superoxide radical scavenging assay (SRSA). The density functional theory (DFT) method using B3LYP energy model and 6-311G++(d,p) basis set was implied to perform the quantum chemical calculation to systematically investigate the antioxidant nature of SN. The principal pathways involved in the antioxidant reactions along with the basic molecular descriptors affecting the antioxidant potentials of a compound were also studied. The results favor the potential of SN as an active ingredient to be used in cosmeceutical formulations.

Potential antioxidant and antiradical agents from Allium ascalonicum: Superoxide dismutase and density functional theory in silico studies

Antioxidants are compounds that can inhibit excessive free radical reactions in the body. Excessive free radicals can cause system imbalances in the body which can trigger oxidative stress and cause serious illness. The limitations of antioxidants in the body can be overcome by consuming safe natural additional antioxidants that can be obtained from natural products. Isolating compounds of Allium ascalonicum leaves as antioxidant and antiradical agents in inhibiting excessive free radicals by in vitro and in silico. The extracted compounds were purified by column chromatography. The compounds obtained were then characterized using ultraviolet, infrared, NMR, and mass spectrometry. Determination of antioxidant activity was carried out by in vitro using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and the non-enzymatic superoxide dismutase (SOD) methods. The in silico study used the density functional theory (DFT) calculation method with global descriptive parameters (GDP), donor acceptor map (DAM), and frontier molecular orbitals (FMO) analysis. Three compounds have been isolated, of which compound 1 is a new compound. In the DPPH method, compound 1 has more strong antioxidant activity than others, as well as in the non-enzymatic SOD method. Whereas, in the DFT calculation shows that compound 1 has the best reactivity and stability between other compounds and was categorized as the best antiradical. Compound 1 has the highest antioxidant activity compared to the other compounds by in vitro both the DPPH and non-enzymatic SOD methods. In silico, compound 1 has the potential as the best antiradical.

Computational-based investigation of antioxidative potential polyphenolic compounds of Salvia officinalis L.: combined DFT and molecular docking approaches

CONTEXT

The antioxidant properties of the three polyphenolic compounds (carnosol, cirsiliol, and luteolin) of Salvia officinalis L. were investigated employing the density functional theory (DFT) calculations at the B3LYP of basis set at 6-311 +  + G (d, p) in order to evaluate their antioxidant activity. The enthalpies of reactions associated with the SET-PT, SPLET, and HAT mechanisms were analyzed in gas and in different solvents using the CPCM (conductor-like polarizable continuum) model. For all possible hydrogen donor sites, the corresponding parameters (BDE, AIP, PDE, PA, ETE, HOMOs, and LUMOs) and reactivity indices (IPE, EA, Χ, η, S, and ω) were also evaluated. The calculated results showed that derivatives 12-OH, 11-OH, 4'-OH, and 3'-OH had the lowest antioxidant activity. The results showed as well that carnosol, cirsiliol, and luteolin have higher reactivity compared to ascorbic acid and could be considered better antioxidants. According to research, the catechol group is crucial in influencing the studied compounds antioxidant activity. The theoretically predicted order of antioxidant efficiencies in this work agrees well with the QSAR (quantitative structure-activity relationship) data. The findings show that in the vacuum as well as benzene media. HAT would be the most effective mechanism; in contrast, the thermodynamic equilibrium approach in polar media is the SPLET mechanism. Likewise, the outcomes of the docking modeling confirm that the selected molecules have high inhibitory activity to glutathione-S-transferases (GSTs) receptors. Moreover, they have very important pharmacokinetic, chemical, and biological profiles. Finally, all the results show that the three natural molecules have good pharmacokinetic profiles, particularly the bioavailability and permeability toward biological membranes.

METHODS

The software packages used in this investigation are Gaussian 16, Discovery studio Visualizer, and AutoDock vina. The three compounds (carnosol, cirsiliol, and luteolin) of Salvia officinalis L. were optimized with DFT/B3LYP of basis set at 6-311 +  + G (d, p). The optimized structures were established via vibrational analysis (i.e., no imaginary frequencies in the frequency set). All enthalpies were zero-point (ZPE) corrected. Vibrational frequency calculations were performed at 298.15 K and 1 atmosphere pressure to determine the thermodynamic characteristics of the investigated reactions. The descriptors were associated with the antioxidant mechanisms for investigated molecules in vacuum and in various solvents. The molecular docking was used by AutoDock vina to estimate and evaluate the title compounds compatibility as potential antioxidant drugs utilizing appropriate receptor proteins. The solvation effect in the medium of benzene (ɛ = 2.27) and water (ɛ = 78.39) was taken into account. Furthermore, a methanol solvent (ɛ = 32.61) was also taken into consideration to compare with the empirical data.

Combining Experimental and Computational Methods to Produce Conjugates of Anticholinesterase and Antioxidant Pharmacophores with Linker Chemistries Affecting Biological Activities Related to Treatment of Alzheimer's Disease

Effective therapeutics for Alzheimer's disease (AD) are in great demand worldwide. In our previous work, we responded to this need by synthesizing novel drug candidates consisting of 4-amino-2,3-polymethylenequinolines conjugated with butylated hydroxytoluene via fixed-length alkylimine or alkylamine linkers (spacers) and studying their bioactivities pertaining to AD treatment. Here, we report significant extensions of these studies, including the use of variable-length spacers and more detailed biological characterizations. Conjugates were potent inhibitors of acetylcholinesterase (AChE, the most active was 17d IC50 15.1 ± 0.2 nM) and butyrylcholinesterase (BChE, the most active was 18d: IC50 5.96 ± 0.58 nM), with weak inhibition of off-target carboxylesterase. Conjugates with alkylamine spacers were more effective cholinesterase inhibitors than alkylimine analogs. Optimal inhibition for AChE was exhibited by cyclohexaquinoline and for BChE by cycloheptaquinoline. Increasing spacer length elevated the potency against both cholinesterases. Structure-activity relationships agreed with docking results. Mixed-type reversible AChE inhibition, dual docking to catalytic and peripheral anionic sites, and propidium iodide displacement suggested the potential of hybrids to block AChE-induced β-amyloid (Aβ) aggregation. Hybrids also exhibited the inhibition of Aβ self-aggregation in the thioflavin test; those with a hexaquinoline ring and C8 spacer were the most active. Conjugates demonstrated high antioxidant activity in ABTS and FRAP assays as well as the inhibition of luminol chemiluminescence and lipid peroxidation in mouse brain homogenates. Quantum-chemical calculations explained antioxidant results. Computed ADMET profiles indicated favorable blood-brain barrier permeability, suggesting the CNS activity potential. Thus, the conjugates could be considered promising multifunctional agents for the potential treatment of AD.

Simultaneously regulating absorption capacities and antioxidant activities of four stilbene derivatives utilizing substitution effect: A theoretical and experimental study against UVB radiation

With the continued depletion of the ozone layer, the sun protection consciousness of humans has gradually enhanced. Long-term ultraviolet (UV) rays exposure will lead to skin tanning, even skin cancer in severe cases, and generate free radicals to cause skin aging. To better protect human skin against UV rays, this work explores the absorption capacities and antioxidant activities of four stilbene derivatives (EHDB, EDMB, EAPD, and HPTP) through the computational chemistry method and DPPH radical scavenging experiment. The research results indicate that their absorption spectra cover the entire UV region, and can effectively protect against UVB radiation. Moreover, three prevailing antioxidant mechanisms: hydrogen atom transfer, sequential proton loss electron transfer, and single electron transfer followed by proton transfer mechanisms, were used to evaluate their antioxidant activities in the ground state. It can be concluded that the O1H1 sites of EHDB and HPTP are the most active, and the SPLET mechanism is the most preferred for the four compounds in ethanol solvent. Furthermore, the DPPH radical scavenging experiment compensates for the theoretical calculation deficiency in the excited state, revealing that the EHDB and HPTP are the most suitable for sunscreen due to their excellent performance on antioxidant capacities, whether before or after sunlight. This work will facilitate EHDB and HPTP to be applied in sunscreen and provide a novel idea in sunscreen research.

Role of the Solvent and Intramolecular Hydrogen Bonds in the Antioxidative Mechanism of Prenylisoflavone from Leaves of Vatairea guianensis

This work discusses the electron structure, antioxidative properties, and solvent contribution of two new antioxidant molecules discovered, named S10 and S11, extracted from a medicinal plant called Vatairea guianensis, found in the Amazon rain-forest. To gain a better understanding, a study using density functional theory coupled with the polarizable-continuum model and the standard 6-311++G(d,p) basis set was conducted. The results indicate that S10 has a higher antioxidant potential than S11, confirming the experimental expectations. In the gas phase, the hydrogen atom transfer route dominates the hydrogen scavenging procedure. However, in the water solvents, the antioxidant mechanism prefers the sequential proton loss electron transfer mechanism. Furthermore, the solvent plays a fundamental role in the antioxidant mechanism. The formation of an intramolecular OH···OCH3 hydrogen bond is crucial for accurately describing the hydrogen scavenging phenomenon, better aligning with the experimental data. The results suggest that the two isoflavones investigated are promising for the pharmacologic and food industries.

Theoretical Study on the Multiple Free Radical Scavenging Reactions of Pyranoanthocyanins

The free radical trapping capacities of multiple pyranoanthocyanins in wine storage and ageing were theoretically explored by density functional theory (DFT) methods. Intramolecular hydrogen bonds were detected in all pyranoanthocyanins, and the planarity of the compounds worsened with an increasing dielectric constant in the environment. Solvents significantly influenced the reaction enthalpies; thus, the preferred thermodynamic mechanisms of the free radical scavenging reactions were modified in different phases. This study incorporates hydrogen atom transfer (HAT), proton loss (PL), electron transfer (ET) reactions, and demethylation (De) of methoxy group mechanisms. The three pyranoanthocyanins have the capacity to capture n1+1 free radicals, where n1 represents the number of methoxy groups. In the gas phase, they prefer employing the n1-De-HAT mechanism on the guaiacyl moiety of the B ring, resulting in the formation of a stable quinone or a quinone radical to scavenge free radicals. In the benzene phase, pyranoanthocyanins trap free radicals via a PL-n1-De-HAT mechanism. In the water phase, the targeted pyranoanthocyanins may dissociate in the form of carboxylate and tend to utilize the n2-PL-n1-De-ET mechanism, where n2 and n1 represent the number of phenolic groups and methoxy groups, respectively, facilitating multiple H+/e- reactions.

A DFT-Based Mechanism Analysis of the Cyclodextrin Inclusion on the Radical Scavenging Activity of Apigenin

Natural flavonoids are renowned for their exceptional antioxidant properties, but their limited water solubility hampers their bioavailability. One approach to enhancing their water solubility and antioxidant activity involves the use of cyclodextrin (CD) inclusion. This study investigated the impact of CD inclusion on the three primary radical scavenging mechanisms associated with flavonoid antioxidant activity, utilizing apigenin as a representative flavonoid and employing density functional theory (DFT) calculations. Initially, the optimized geometries of CD-apigenin inclusion complexes were analyzed, revealing the formation of hydrogen bonds between CD and apigenin. In less polar environments, the inclusion complex strengthened the bond dissociation enthalpies of hydroxyl groups, thereby reducing antioxidant activity. Conversely, in polar environments, the inclusion complex had the opposite effect by lowering proton affinity. These findings align with experimental results demonstrating that CD inclusion complexation enhances flavonoid antioxidant activity in aqueous ethanol solutions.

Mechanistic insight into the free radical scavenging and xanthine oxidase (XO) inhibitor potent of monoacetylphloroglucinols (MAPGs)

Three novel antioxidant candidates based on phenolic polyketide, monoacetylphloroglucinol (MAPG), a natural antibiotic compound produced by plant growth-promoting rhizobacteria (PGPR), Pseudomonas fluorescens F113 have been proposed. Initially, a green and highly efficient route to the synthesis of MAPG and its two analogues from phloroglucinol (PG) has been developed. Afterward, their rational mechanism of antioxidant activity has been investigated based on thermodynamic descriptors involved in the double ( 2H+/2e-) radical trapping processes. These calculations have been performed using the systematic density functional theory (DFT) method at the B3LYP/Def2-SVP level of theory in the gas phase and aqueous solution. Our findings reveal that the double formal hydrogen atom transfer (df-HAT) mechanism is preferred in the gas phase, while the double sequential proton loss electron transfer (dSPLET) mechanism is preferred in aqueous solution for all MAPGs. The 6-OH group represents the most favourable site for trapping radical species for all MAPGs, which is supported by the pK_a values obtained from DFT calculations. The role of acyl substituents on the PG ring has been comprehensively discussed. The presence of acyl substituents has a strong influence on the thermodynamic parameters of the phenolic O-H bond in PG. These results are supported by frontier molecular orbitals (FMOs) analysis, where the addition of acyl substituents increases the chemical reactivity of MAPGs significantly. Based on molecular docking and molecular dynamics simulations (MDs), MAPGs are also predicted to be promising candidates for xanthine oxidase (XO) inhibition.HighlightsThe antioxidant activity of the three synthesised MAPGs has been investigated using the DFT method.Acyl substituents increase the chemical reactivity and antioxidant activity of MAPGs.df-HAT is the preferred mechanism in the gas phase.dSPLET seems to be more favoured in aqueous solution.MAPGs are expected to be promising xanthine oxidase (XO) inhibitors.

Influence of the pKa value on the antioxidant activity of licorice flavonoids under solvent-mediated effects

Licorice flavonoids (LCFs) have been widely used in food care and medical treatment due to their significant antioxidant activities. However, the molecular mechanism of their antioxidant activity remains unclear. Therefore, network pharmacology, ADMET, density functional theory (DFT), molecular docking, and molecular dynamics (MD) simulation were employed to explore the molecular mechanism of the antioxidant effects of LCF. The network pharmacology and ADMET studies showed that the active molecules of kumatakenin (pK_a  = 6.18), licoflavonol (pK_a  = 6.86), and topazolin (pK_a  = 6.21) in LCF are key antioxidant components and have good biosafety. Molecular docking and MD simulation studies demonstrated that active molecules interacted with amino acid residues in target proteins to form stable protein-ligand complexes and exert their antioxidant effects. DFT studies showed that the antioxidant activity of LCF could be significantly modulated under the solvent-mediated effect. In addition, based on the derivation of the Henderson-Hasselbalch and van't Hoff formulas, the functional relationships between the reaction-free energy (ΔG) of LCF and the pH and pK_a values were established. The results showed that active molecules with larger pK_a values will be more conducive to the improvement of their antioxidant activity under solvent-mediated effects. In conclusion, this study found that increasing the pK_a value of LCF would be an effective strategy to improve their antioxidant activity under the effect of solvent mediation. The pK_a value of an LCF will be a direct standard to evaluate its solvent-mediated antioxidant activity. This study will provide theoretical guidance for the development of natural antioxidants.

Antioxidant mechanisms and products of four 4',5,7-trihydroxyflavonoids with different structural types

4',5,7-OHs are common substituents of natural flavonoids, a type of effective phenolic antioxidant. However, the antioxidant processes between 4',5,7-trihydroxyflavonoids with different structural types have not been compared systematically, and the antioxidant products are challenging to determine. This study compared four 4',5,7-trihydroxyflavonoids, including apigenin, genistein, kaempferol, and naringenin. In quantum chemical analyses, the four 4',5,7-trihydroxyflavonoids showed different thermodynamic properties, and the C4'-OH (or C3-OH of kaempferol) possessed the strongest activity. Moreover, the reaction rate constants were larger when a hydrogen atom was transferred from C4'-OH (or C3-OH of kaempferol) than from C5-OH. When different atoms were linked to 2,2-diphenyl-1-picrylhydrazyl radical (DPPH˙), the C3'-DPPH adducts showed the smallest energy. In experimental assays, the scavenging ability for neutral free radicals, radical cations, and radical anions was negatively correlated with the corresponding theoretical parameters. Finally, mass spectroscopy detected the apigenin-DPPH˙, genistein-DPPH˙, and naringenin-DPPH˙ adduct peaks. In conclusion, the structural type of 4',5,7-trihydroxyflavonoids can affect the antioxidant ability, site, and speed, but not the mechanism. After hydrogen abstraction at C4'-OH, 4',5,7-trihydroxyflavones, 4',5,7-trihydroxyisoflavones, and 4',5,7-trihydroxyflavanones will produce antioxidant products via C3'-radical linking.

Density Functional Theory Study on Antioxidant Activity of Three Polyphenols

In recent years, research on the antioxidant activity of natural antioxidants has become more and more popular. Polyphenols are a large number of natural antioxidants in plants. This paper selected three common polyphenols to study their antioxidant activity based on quantum chemistry theory. This experiment hopes to provide a theoretical basis for the further development of polyphenol health food with strong antioxidant activity. Three polyphenols resveratrol, liquiritigenin, and isoliquiritigenin were optimized at the level of B3lyp/6-311G (d, p), and the single point energy was calculated with B3lyp/6-311 +  + G (2d, 2p). The phenol hydroxyl bond dissociation enthalpy (BDE), ionization potential (IP), proton dissociation enthalpy (PDE), proton affinity (PA), and electron transfer enthalpy (ETE) were calculated in different phase states study the antioxidant mechanism. Draw the frontier molecular orbital and conduct dynamic simulation analysis scavenging · OH and · OOH to explore the most possible active sites in different phenolic hydroxyl sites. The bond length, dihedral angle, BDE, IP, PDE, PA and ETE were compared to speculate the antioxidant activity: Resveratrol > isoliquiritigenin > liquiritigenin. By analyzing the frontier molecular orbital and dynamic simulation results, it is speculated that the phenolic hydroxyl groups at C4', C4', and C4 are the most likely active sites of resveratrol, liquiritigenin, and isoliquiritigenin, respectively. In different phase states, the three compounds showed the same antioxidant activity, and the phenolic hydroxyl activities of the three compounds were different at different sites.

Structure-activity relationship of antioxidant prenylated (iso)flavonoid-type compounds: quantum chemistry and molecular docking studies

Prenylated (iso)flavonoid-type compounds are a subclass of natural flavonoids that have been reported to exhibit good antioxidant properties. In the present paper, the structure-activity relationship of three typical prenylated (iso)flavonoids namely 8-prenyldaidzein (Per), Licoflavone (Lic), and erysubin F (Ery) have been determined using DFT (density functional theory)-based calculations and molecular docking studies. As result, the CH bond of the prenyl substituent was found to be the most thermodynamically favorable site for trapping free radicals in the gas phase and lipid physiological environments. While the OH bond of the B-ring seems to be more reactive in water. HAT (hydrogen atom transfer) and SPLET (sequential proton loss electron transfer) play a decisive role in the antiradical activity of the studied compounds in lipid and polar physiological environments, respectively. All of the studied compounds exhibit strong binding affinity to both xanthine oxidase and inducible nitric oxide synthase enzymes by forming several hydrogen bonds and hydrophobic interactions with their respective catalytic sites. These results suggest that (iso)flavonoid-type compounds are promising radical scavengers and antioxidants. Communicated by Ramaswamy H. Sarma.

Flavanones from Erythrina crista-galli Twigs and Their Antioxidant Properties Determined through In Silico and In Vitro Studies

Flavonoids are a secondary metabolite group with various bioactivities, such as antioxidants. They are rich in the genus Erythrina, such as Erythrina crista-galli. This research aims to isolate and characterize flavonoids from the twigs of E. crista-galli and determine their antioxidant properties through in silico and in vitro assays. The ethyl acetate extract of E. crista-galli twigs were separated by column chromatography and characterized using spectroscopic methods. Density functional theory (DFT) calculations were performed on the isolated flavonoids and the reference compounds (ascorbic acid and quercetin) to obtain global descriptive parameters and a donor–acceptor map (DAM). We successfully isolated lupinifolin (1) and citflavanone (2) for the first time from E. crista-galli, along with lonchocarpol A (3), which has been discovered previously. The DAM suggests that these flavanones are good antiradicals with effective electron donors. However, they tend to be electron acceptors in methanol. The frontier molecular orbital analysis implies that lupinifolin (1) is a better antiradical than the other flavanones. The DPPH assays show that lupinifolin (1) has the highest antioxidant (antiradical) activity, with an IC50 value of 128.64 ppm. The in silico studies showed similar trends to the in vitro assays using the DPPH method.

Antioxidant Potential of Santowhite as Synthetic and Ascorbic Acid as Natural Polymer Additives

A wide variety of additives are used to improve specific characteristics of the final polymeric product. Antioxidant additives (AAs) can prevent oxidative stress and thus the damage of polymeric materials. In this work, the antioxidant potential and thus the applicability of Santowhite (SW) as synthetic and ascorbic acid (Asc) as natural AAs were explored by using computational tools. Two density functional theory (DFT) methods, M05-2X and M06-2X, have been applied in combination with the 6-311++G(2d,2p) basis set in gas phase. Three antioxidant mechanisms have been considered: hydrogen atom transfer (HAT), single electron transfer-proton transfer (SET-PT), and sequential proton loss electron transfer (SPLET). Bond dissociation enthalpy (BDE), ionization potential (IP), proton dissociation enthalpy (PDE), proton affinity (PA), and electron transfer enthalpy (ETE) have been computed for each potential hydrogen donor site. The results indicate that the antioxidant potential of Asc is higher than SW. Furthermore, some of the C-H bonds, depending on their position in the structures, are potent radical scavengers, but O-H groups are more prone to donate H-atoms to free radicals. Nonetheless, both additives can be potentially applied to safeguard common polymers and prohibit oxidative stress-induced material deterioration.

Radical Scavenging Mechanisms of Phenolic Compounds: A Quantitative Structure-Property Relationship (QSPR) Study

Due to their antioxidant properties, secondary plant metabolites can scavenge free radicals such as reactive oxygen species and protect foods from oxidation processes. Our aim was to study structural influences, like basic structure, number of hydroxyl groups and number of Bors criteria on the outcome of the oxygen radical absorbance capacity (ORAC) assay. Furthermore, similarities and differences to other in vitro antioxidant assays were analyzed by principal component analysis. Our studies confirmed that the antioxidant behavior in the ORAC assay is dominated by the number and types of substituents and not by the Bors criteria, as long as no steric hindrance occurs. For example, morin (MOR) with five hydroxyl groups and two Bors criteria reached an area under the curve of (3.64 ± 0.08) × 105, which was significantly higher than quercetin-7-D-glucoside (QGU7) (P < 0.001), and thus the highest result. Principal component analysis showed different dependencies regarding structural properties of Folin-Ciocalteu (FC)- and 2,2-diphenyl-1-picrylhydrazyl (DPPH)-assays or 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS)- and ORAC-assays, respectively. Therefore, we conclude that they are based on different reaction mechanisms. The number of hydroxyl groups showed a stronger influence on the antioxidant activity than the Bors criteria. Due to these differences, the correlation of these rapid tests to specific applications should be validated.

Review on the Regulation of Plant Polyphenols on the Stability of Polyunsaturated-Fatty-Acid-Enriched Emulsions: Partitioning Kinetic and Interfacial Engineering

The plant polyphenols are normally presented as natural functional antioxidants, which also possess the potential ability to improve the physicochemical stability of polyunsaturated fatty acid (PUFA)-enriched emulsions by interface engineering. This review discussed the potential effects of polyphenols on the stability of PUFA-enriched emulsions from the perspective of the molecular thermodynamic antioxidative analysis, the kinetic of interfacial partitioning, and the covalent and non-covalent interactions with emulsifiers. Recently, research studies have proven that the interfacial structure of emulsions can be concurrently optimized via promoting interfacial partitioning of polyphenols and further increasing interfacial thickness and strength. Moreover, the applied limitations of polyphenols in PUFA-enriched emulsions were summarized, and then some valuable and constructive viewpoints were put forward in this review to provide guidance for the use of polyphenols in constructing PUFA-enriched emulsions.

Mechanism of Antioxidant Activity of Betanin, Betanidin and Respective C15-Epimers via Shape Theory, Molecular Dynamics, Density Functional Theory and Infrared Spectroscopy

Betanin and betanidin are compounds with extensive interest; they are effectively free radical scavengers. The present work aims to elucidate the differences between the mechanism of the antioxidant activity of betanin, betanidin, and their respective C15-epimers. Shape Theory establishes comparisons between the molecules’ geometries and determines parallelisms with the descriptors BDE, PA, ETE IP, PDE, and infrared spectra (IR) obtained from the molecule simulations. Furthermore, the molecules were optimized using the B3LYP/6-31+G(d,p) protocol. Finally, the molecular docking technique analyzes the antioxidant activity of the compounds in the complex with the therapeutic target xanthine oxidase (XO), based on a new proposal for the geometrical arrangement of the ligand atoms in the framework of Shape Theory. The results obtained indicate that the SPLET mechanism is the most favorable in all the molecules studied and that the first group that loses the hydrogen atom in the four molecules is the C17COOH, presenting less PA the isobetanidin. Furthermore, regarding the molecular docking, the interactions of these compounds with the target were favorable, standing out to a greater extent the interactions of isobetanidin with XO, which were analyzed after applying molecular dynamics.

Structure-antioxidant activity relationships of dendrocandin analogues determined using density functional theory

Quantum-chemical calculations based on the density functional theory (DFT) at the B3LYP/6-311 + + G(2d,2p)//B3LYP/6-31G(d,p) level were employed to study the relationship between the antioxidant properties and chemical structures of six dendrocandin (DDCD) analogues in the gas phase and two solvents (methanol and water). The hydrogen atom transfer (HAT), electron-transfer-proton-transfer (ET-PT), and sequential proton-loss-electron-transfer (SPLET) mechanisms are explored. The highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), reactivity indices (η, μ, ω, ω +, and ω - ), and molecular electrostatic potentials (MEPs) were also evaluated. The results suggest that the D ring plays an important role in mediating the antioxidant activity of DDCDs. For all the studied compounds, indicating that HAT was identified as the most favorable mechanism, whereas the SPLET mechanism was the most thermodynamically favorable pathway in polar solvents. The results of our study should aid in the development of new or modified antioxidant compounds.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11224-022-01895-2.

Mechanistic and Kinetic Studies of the Radical Scavenging Activity of 5-O-Methylnorbergenin: Theoretical and Experimental Insights

5-O-Methylnorbergenin (5-OMB), a natural compound isolated from Rourea harmandiana, is a compound with potential antioxidant activity based on its chemical structure; however, this activity has not been investigated thus far. In this study, the antioxidant activity of 5-OMB was evaluated by experimental and computational methods. 5-OMB exhibited high activity in DPPH (IC₅₀ = 7.25 ± 0.94 μM) and ABTS^•+ (IC₅₀ = 4.23 ± 0.12 μM) assays, higher than the reference compound Trolox. The computational results consistently show that 5-OMB is an excellent HOO^• radical scavenger (k_overall = 8.14 × 10⁸ M^-1 s^-1) in water at physiological pH, however it only exerts weak activity in lipid medium (k_overall = 3.02 × 10² M^-1 s^-1). The reaction follows the formal hydrogen transfer mechanism in nonpolar solvents, whereas both the sequential proton loss electron transfer and the formal hydrogen transfer pathways contribute to the activity in aqueous solution. There is a good agreement between experimental and computational data, suggesting that 5-OMB is a promising natural radical scavenger in aqueous physiological environment.

Theoretical insights into the antiradical activity and copper-catalysed oxidative damage of mexidol in the physiological environment

Mexidol (MD, 2-ethyl-6-methyl-3-hydroxypyridine) is a registered therapeutic agent for the treatment of anxiety disorders. The chemical structure suggests that MD may also act as an antioxidant. In this study, the hydroperoxyl radical scavenging activity of MD was studied to establish baseline antioxidant activity, followed by an investigation of the effect of MD on the copper-catalysed oxidative damage in biological systems, using computational methods. It was found that MD exhibits moderate radical scavenging activity against HOO• in water and pentyl ethanoate solvents following the single electron transfer and formal hydrogen transfer mechanisms, respectively. MD can chelate Cu(II), forming complexes that are much harder to reduce than free Cu(II): MD chelation completely quenches the Cu(II) reduction by ascorbic acid and suppresses the rate of reduction reaction byO 2 ⋅ - that are the main reductants of Cu(II) in biological environments. Therefore, MD exerts its anti-HO• activity primarily as an OIL-1 inhibitor.

Theoretical study on the radical scavenging activity and mechanism of four kinds of Gnetin molecule

As an important subgroup of resveratrol oligomers, Gnetins received much attention due to their antioxidants. The four Gnetin molecules are divided into two major categories according to different structures, type-A (Gnetin-C, Gnetin-D) and type-B (Gnetin-L, Gnetin-F). Density functional theory (DFT) has been performed thermodynamically and kinetically in detail to analyze the structure and antioxidant activity of four Gnetins toward OH/OOH radical in the gas and solvents phase with four possible antioxidant mechanisms, namely, Hydrogen-atom transfer (HAT), Single electron transfer followed by proton transfer (SET-PT), Sequential proton-loss electron transfer (SPLET), and Radical adduct formation (RAF). From these calculations; Gnetins' order of antioxidant activity was estimated as: Gnetin-C ≈ Gnetin-L > Resveratrol > Gnetin-D > Gnetin-F. All investigations suggested that type A has a higher radical scavenging activity compared to type B. On the basis of the structure-activity relationship, type A structure may have more vital antioxidant potential in the future.

Efficient synthesis, and antitumor and antioxidant activities of polyhydroxybenzophenone

Five polyhydroxybenzophenones were synthesized, then their antitumor and antioxidant activities were evaluated. Compounds 1-3 and 5 exhibited obvious antitumor activity. Among them, compounds 1 and 2 exhibited stronger cytotoxicity against hepatocarcinoma SMMC-7721 cells than cisplatin, with half maximal inhibitory concentrations (IC₅₀) of approximately 3.86 and 5.32 μM, respectively. Compounds 1, 2, and 3 exhibited stronger antioxidant activity than trolox, with IC₅₀ values of 11.15, 10.15, and 8.91 μM, respectively, and the antioxidant mechanism and strength of all compounds were further verified using computational chemistry. These results demonstrated that compounds 1-3 and 5 were very promising leads for further structural modification.

Antioxidant Activity of Natural Samwirin A: Theoretical and Experimental Insights

Samwirin A (SW), a natural compound isolated from Sambucus williamsii or Rourea harmandiana, is known to exhibit potent antiosteoporosis activity and promote cell proliferation in rat osteoblast-like UMR 106 cells. Antiosteoporosis activity suggests that the compound must also exhibit antioxidant activity but this has not been studied thus far. In the present study, the antioxidant activity of SW was examined by experimental and computational studies. It was found that SW exhibits good hydroperoxyl scavenging activity, particularly in water at physiological pH (k overall = 1.01 × 107 M-1 s-1). The single-electron transfer mechanism defines the HOO• + SW reaction in water, while the activity in the lipid medium is moderate and it follows the formal hydrogen transfer mechanism. The rate constant of the HOO• scavenging reaction in the aqueous solution is about 78 times higher than the reference compound Trolox. The computational results are in line with experimental data underscoring that SW is a promising radical scavenger in aqueous media at physiological pH.

Multiple free radical scavenging reactions of aurones

A series of naturally occurring 3',4'-dihydroxy aurones have been studied with regard to multiple free radical scavenging reactions in the gas and two liquid phases using density functional theory (DFT). All of the aurones prefer to perform (2 + n)-HAT mechanism to trap 2 + n free radicals, where n is the sum of the numbers of catechol and guaiacyl units in the gas and benzene phases. The second HAT reaction favours occurring in the same catechol moiety of the first HAT mechanism occurring OH group due to the formation of a stable quinone and the highly exothermic step of the final stable product formation. The catechol and guaiacyl moieties show increased potency for the second and fourth H⁺/e^‒ reactions. In the water phase, aurones can perform multiple H⁺/e^‒ reactions through n₁PL-ET-n₂HAT-(n+1-n₂)ET mechanism, where n₁ is the number of OH groups and n₂ is the number of guaiacyl moieties.

Multiple free radical scavenging reactions of aurones

A series of naturally occurring 3',4'-dihydroxy aurones have been studied with regard to multiple free radical scavenging reactions in the gas and two liquid phases using density functional theory (DFT). All of the aurones prefer to perform (2 + n)-HAT mechanism to trap 2 + n free radicals, where n is the sum of the numbers of catechol and guaiacyl units in the gas and benzene phases. The second HAT reaction favours occurring in the same catechol moiety of the first HAT mechanism occurring OH group due to the formation of a stable quinone and the highly exothermic step of the final stable product formation. The catechol and guaiacyl moieties show increased potency for the second and fourth H⁺/e^‒ reactions. In the water phase, aurones can perform multiple H⁺/e^‒ reactions through n₁PL-ET-n₂HAT-(n+1-n₂)ET mechanism, where n₁ is the number of OH groups and n₂ is the number of guaiacyl moieties.

Physicochemical, antioxidant properties of carotenoids and its optoelectronic and interaction studies with chlorophyll pigments

The physicochemical and antioxidant properties of seven carotenoids: antheraxanthin, β-carotene, neoxanthin, peridinin, violaxanthin, xanthrophyll and zeaxanthin were studied by theoretical means. Then the Optoelectronic properties and interaction of chlorophyll-carotenoid complexes are analysed by TDDFT and IGMPLOT. Global reactivity descriptors for carotenoids and chlorophyll (Chla, Chlb) are calculated via conceptual density functional theory (CDFT). The higher HOMO-LUMO (HL) gap indicated structural stability of carotenoid, chlorophyll and chlorophyll-carotenoid complexes. The chemical hardness for carotenoids and Chlorophyll is found to be lower in the solvent medium than in the gas phase. Results showed that carotenoids can be used as good reactive nucleophile due to lower µ and ω. As proton affinities (PAs) are much lower than the bond dissociation enthalpies (BDEs), it is anticipated that direct antioxidant activity in these carotenoids is mainly due to the sequential proton loss electron transfer (SPLET) mechanism with dominant solvent effects. Also lower PAs of carotenoid suggest that antioxidant activity by the SPLET mechanism should be a result of a balance between proclivities to transfer protons. Reaction rate constant with Transition-State Theory (TST) were estimated for carotenoid-Chlorophyll complexes in gas phase. Time dependent Density Functional Theory (TDDFT) showed that all the chlorophyll (Chla, Chlb)-carotenoid complexes show absorption wavelength in the visible region. The lower S1-T1 adiabatic energy gap indicated ISC transition from S1 to T1 state.

Green One-Pot Synthesis of Coumarin-Hydroxybenzohydrazide Hybrids and Their Antioxidant Potency

Compounds from the plant world that possess antioxidant abilities are of special importance for the food and pharmaceutical industry. Coumarins are a large, widely distributed group of natural compounds, usually found in plants, often with good antioxidant capacity. The coumarin-hydroxybenzohydrazide derivatives were synthesized using a green, one-pot protocol. This procedure includes the use of an environmentally benign mixture (vinegar and ethanol) as a catalyst and solvent, as well as very easy isolation of the desired products. The obtained compounds were structurally characterized by IR and NMR spectroscopy. The purity of all compounds was determined by HPLC and by elemental microanalysis. In addition, these compounds were evaluated for their in vitro antioxidant activity. Mechanisms of antioxidative activity were theoretically investigated by the density functional theory approach and the calculated values of various thermodynamic parameters, such as bond dissociation enthalpy, proton affinity, frontier molecular orbitals, and ionization potential. In silico calculations indicated that hydrogen atom transfer and sequential proton loss-electron transfer reaction mechanisms are probable, in non-polar and polar solvents respectively. Additionally, it was found that the single-electron transfer followed by proton transfer was not an operative mechanism in either solvent. The conducted tests indicate the excellent antioxidant activity, as well as the low potential toxicity, of the investigated compounds, which makes them good candidates for potential use in food chemistry.

Antioxidant Activity and Mechanism of Avenanthramides: Double H+/e- Processes and Role of the Catechol, Guaiacyl, and Carboxyl Groups

Avenanthramides (AVAs), unique phenolic compounds in oats, have attracted increasing interest due to their health benefits. Eight representative AVAs were studied using the density functional theory (DFT) method to elucidate their antioxidant activity and mechanism. Preference of different mechanisms was evaluated based on thermodynamic descriptors involved in double (2H⁺/2e^-) free radical scavenging reactions. It was found that the hydrogen atom transfer (HAT) mechanism is more favorable in the gas and benzene phases, while sequential proton loss electron transfer (SPLET) is preferred in polar media. The results suggest the feasibility of the double HAT and double SPLET mechanisms for 2s and c-series AVAs. The sequential triple proton loss double electron transfer (StPLdET) mechanism represents the dominant pathway in aqueous solution at physiological pH. In addition, the sequential proton loss hydrogen atom transfer (SPLHAT) mechanism provides an alternative pathway to trap free radicals. Results also revealed the important role of the catechol, guaiacyl, and carboxyl moieties.

Theoretical investigations on the antioxidant potential of a non-phenolic compound thymoquinone: a DFT approach

Thymoquinone (TQ) is a natural compound present in black cumin which possesses potent antioxidant activity without having any phenolic hydroxyl group which is responsible for antioxidant activity. In the present study, computational calculation based on density functional theory (DFT) was executed to assess systematically the antioxidant behavior of this compound by considering geometrical characteristics, highest occupied molecular orbital - lowest unoccupied molecular orbital (HOMO-LUMO), and molecular electrostatic potential (MEP) surface. Thermochemical parameters correlated to the leading antioxidant mechanisms such as hydrogen atom transfer (HAT), single electron transfer-proton transfer (SETPT), and sequential proton loss electron transfer (SPLET) were studied in gas and water media. In addition, the changes of thermochemical parameters such as free energy change (∆G) and enthalpy change (∆H) were computed for hydrogen abstraction (HA) from TQ to hydroxyl radical in gas and water phases to investigate its free radical scavenging potency. The low and comparable values of bond dissociation enthalpy (BDE), proton dissociation enthalpy (PDE), ionization potential (IP), proton affinity (PA), and electron transfer enthalpy (ETE) revealed the antioxidant activity. The ∆G and ∆H also indicated apposite thermodynamic evidence in favor of antiradical capability of TQ. The attack of the free radical occurred preferentially at 3CH position of the molecule.

The Use of Chinese Skullcap (Scutellaria baicalensis) and Its Extracts for Sustainable Animal Production

Simple Summary

With the increasing pressure to address the problems of bacterial resistance and drug residues, medicinal herbs are gradually taking a more important role in animal production. Scutellaria baicalensis is a common and widely used Chinese medicinal herb. The main bioactive compounds in the plant are baicalein and baicalin. These compounds have many biological functions including anti-oxidation, antipyretic, analgesic, anti-inflammatory, antiallergic, antimicrobial, immunomodulatory, and antitumor effects. S. baicalensis and its extracts can effectively promote animal growth, improve the production performance of dairy cows, reduce the stress and inflammatory response, and have effective therapeutic effects on diseases caused by bacteria, viruses, and other pathogenic microorganisms. This paper summarizes the biological function of S. baicalensis and its application in sustainable animal production to provide a reference for future application of S. baicalensis and other medicinal herbs in animal production and disease treatment.

Abstract

Drugs have been widely adopted in animal production. However, drug residues and bacterial resistance are a worldwide issue, and thus the most important organizations (FAO, USDA, EU, and EFSA) have limited or banned the use of some drugs and the use of antibiotics as growth promoters. Natural products such as medicinal herbs are unlikely to cause bacterial resistance and have no chemical residues. With these advantages, medicinal herbs have long been used to treat animal diseases and improve animal performance. In recent years, there has been an increasing interest in the study of medicinal herbs. S. baicalensis is a herb with a high medicinal value. The main active compounds are baicalin and baicalein. They may act as antipyretic, analgesic, anti-inflammatory, antiallergenic, antimicrobial, and antitumor agents. They also possess characteristics of being safe, purely natural, and not prone to drug resistance. S. baicalensis and its extracts can effectively promote the production performance of livestock and treat many animal diseases, such as mastitis. In this review, we summarize the active compounds, biological functions, and applications of S. baicalensis in the production of livestock and provide a guideline for the application of natural medicines in the production and treatment of diseases.