Antioxidant Motifs in Flavonoids: O-H versus C-H Bond Dissociation

Antioxidant activity of Zuccagnia-type propolis: A combined approach based on LC-HRMS analysis of bioanalytical-guided fractions and computational investigation

This study reports a combined approach to assess the antioxidant activity of Zuccagnia-type propolis. Fractions exhibiting the highest antioxidant activities evidenced by DPPH, a β-carotene bleaching and superoxide radical scavenging activity-non-enzymatic assays, were processed by LC-HRMS/MS to characterize the relevant chemical compounds. A computational protocol based on the DFT calculations was used to rationalize the main outcomes. Among the 28 identified flavonoids, caffeic acids derivatives were in the fraction exhibiting the highest antioxidant activity, with 1-methyl-3-(4'-hydroxyphenyl)-propyl caffeic acid ester and 1-methyl-3-(3',4'-dihydroxyphenyl)-propyl caffeic acid ester as major components. Results clearly showed roles of specific chemical motifs, which can be supported by the computational analysis. This is the first report ascribing the antioxidant ability of Zuccagnia-type propolis to its content in specific caffeic acid derivatives, a potential source of radical scavenging phytochemicals. The proposed protocol can be extended to the study of other plant-products to address the most interesting bioactive compounds.

Identification of Antioxidant Methyl Derivatives of Ortho-Carbonyl Hydroquinones That Reduce Caco-2 Cell Energetic Metabolism and Alpha-Glucosidase Activity

α-glucosidase, a pharmacological target for type 2 diabetes mellitus (T2DM), is present in the intestinal brush border membrane and catalyzes the hydrolysis of sugar linkages during carbohydrate digestion. Since α-glucosidase inhibitors (AGIs) modulate intestinal metabolism, they may influence oxidative stress and glycolysis inhibition, potentially addressing intestinal dysfunction associated with T2DM. Herein, we report on a study of an ortho-carbonyl substituted hydroquinone series, whose members differ only in the number and position of methyl groups on a common scaffold, on radical-scavenging activities (ORAC assay) and correlate them with some parameters obtained by density functional theory (DFT) analysis. These compounds' effect on enzymatic activity, their molecular modeling on α-glucosidase, and their impact on the mitochondrial respiration and glycolysis of the intestinal Caco-2 cell line were evaluated. Three groups of compounds, according their effects on the Caco-2 cells metabolism, were characterized: group A (compounds 2, 3, 5, 8, 9, and 10) reduces the glycolysis, group B (compounds 1 and 6) reduces the basal mitochondrial oxygen consumption rate (OCR) and increases the extracellular acidification rate (ECAR), suggesting that it induces a metabolic remodeling toward glycolysis, and group C (compounds 4 and 7) increases the glycolysis lacking effect on OCR. Compounds 5 and 10 were more potent as α-glucosidase inhibitors (AGIs) than acarbose, a well-known AGI with clinical use. Moreover, compound 5 was an OCR/ECAR inhibitor, and compound 10 was a dual agent, increasing the proton leak-driven OCR and inhibiting the maximal electron transport flux. Additionally, menadione-induced ROS production was prevented by compound 5 in Caco-2 cells. These results reveal that slight structural variations in a hydroquinone scaffold led to diverse antioxidant capability, α-glucosidase inhibition, and the regulation of mitochondrial bioenergetics in Caco-2 cells, which may be useful in the design of new drugs for T2DM and metabolic syndrome.

Steam Explosion Pretreatment of Polysaccharide from Hypsizygus marmoreus: Structure and Antioxidant Activity

This paper investigated the effects of steam explosion (SE) pretreatment on the structural characteristics and antioxidant activity of Hypsizygus marmoreus polysaccharides (HPS). Hypsizygus marmoreus samples were pretreated at different SE temperatures (120-200 °C) and polysaccharides were extracted using the water extraction and alcohol precipitation method. The results showed that SE pretreatment improved the extraction rate of HPS. Under the conditions of SE treatment time of 60 s and temperature of 160 °C, the extraction rate of HPS was the highest (8.78 ± 0.24%). After SE pretreatment, the structural changes of HPS tended to enhance the antioxidant activity, which showed that the content of Gal and Man in the monosaccharide composition increased and the molecular weight decreased. When testing antioxidant activity in vitro, the ability of SE-pretreated HPS to scavenge DPPH radicals, hydroxyl radicals, and superoxide anion radicals was better than that of HPS without SE pretreatment. Our findings shed light on SE pretreatment as an efficient method for extracting active polysaccharides, providing a new way to improve their extraction rate and biological activity.

Computational Chemistry Strategies to Investigate the Antioxidant Activity of Flavonoids-An Overview

Despite several decades of research, the beneficial effect of flavonoids on health is still enigmatic. Here, we focus on the antioxidant effect of flavonoids, which is elementary to their biological activity. A relatively new strategy for obtaining a more accurate understanding of this effect is to leverage computational chemistry. This review systematically presents various computational chemistry indicators employed over the past five years to investigate the antioxidant activity of flavonoids. We categorize these strategies into five aspects: electronic structure analysis, thermodynamic analysis, kinetic analysis, interaction analysis, and bioavailability analysis. The principles, characteristics, and limitations of these methods are discussed, along with current trends.

Responses to lead stress in Scrophularia striata: insights into antioxidative defence mechanisms and changes in flavonoids profile

Lead (Pb) induces oxidative stress in plants, which results in different responses, including the production of antioxidants and changes in the profile of secondary metabolites. In this study, the responses of Scrophularia striata exposed to 250mgL-1 Pb (NO3 )2 in a hydroponic environment were determined. Growth parameters, oxidative and antioxidative responses, redox status, and the concentration of Pb were analysed in roots and shoots. Malondialdehyde and hydrogen peroxide (H2 O2 ) levels in the roots were significantly increased and reached their highest value at 72h after Pb treatment. Superoxide dismutase, catalase, and peroxidase, as an enzymatic antioxidant system, were responsible for reactive oxygen species scavenging, where their activities were increased in the shoot and root of Pb-treated plants. Enzymatic antioxidant activities were probably not enough to remove a significant H2 O2 content in response to Pb treatment. Therefore, other defence responses were activated. The results stated that the flavonoid components of S. striata progressed towards the increase of isoflavone, flavanol, and stilbenoid contents under Pb treatment. In general, S. striata stimulates the enzymatic defence system and activates the non-enzymatic system by modulating the profile of flavonoids toward the production of flavonoids with high antioxidant activity, such as quercetin and myricetin in response to Pb stress.

Redox-Mediated Amination of Pyrogallol-Based Polyphenols

Flavonoids are known to covalently modify amyloidogenic peptides by amination reactions. The underlying coupling process between polyphenols and N-nucleophiles is assessed by several in vitro and in silico approaches. The coupling reaction involves a sequence of oxidative dearomatization, amination, and reductive amination (ODARA) reaction steps. The C6-regioselectivity of the product is confirmed by crystallographic analysis. Under aqueous conditions, the reaction of baicalein with lysine derivatives yields C-N coupling as well as hydrolysis products of transient imine intermediates. The observed C-N coupling reactions work best for flavonoids combining a pyrogallol substructure with an electron-withdrawing group attached to the C4a-position. Thermodynamic properties such as bond dissociation energies also highlight the key role of pyrogallol units for the antioxidant ability. Combining the computed electronic properties and in vitro antioxidant assays suggests that the studied pyrogallol-containing flavonoids act by various radical-scavenging mechanisms working in synergy. Multivariate analysis indicates that a small number of descriptors for transient intermediates of the ODARA process generates a model with excellent performance (r=0.93) for the prediction of cross-coupling yields. The same model has been employed to predict novel antioxidant flavonoid-based molecules as potential covalent inhibitors, opening a new avenue to the design of therapeutically relevant anti-amyloid compounds.

Phytochemical Profiling and Antioxidant Activities of the Most Favored Ready-to-Use Thai Curries, Pad-Ka-Proa (Spicy Basil Leaves) and Massaman

Food is one of the factors with the highest impact on human health. Today, attention is paid not only to food properties such as energy provision and palatability but also to functional aspects including phytochemical, antioxidant properties, etc. Massaman and spicy basil leaf curries are famous Thai food dishes with a good harmony of flavor and taste, derived from multiple herbs and spices, including galangal rhizomes, chili pods, garlic bulbs, peppers, shallots, and coriander seeds, that provide an array of health benefits. The characterization of phytochemicals detected by LC-ESI-QTOF-MS/MS identified 99 components (Masaman) and 62 components (spicy basil leaf curry) such as quininic acid, hydroxycinnamic acid, luteolin, kaempferol, catechin, eugenol, betulinic acid, and gingerol. The cynaroside and luteolin-7-O-glucoside found in spicy basil leaf curry play a key role in antioxidant activities and were found at a significantly higher concentration than in Massaman curry. Phenolic and flavonoid compounds generally exhibit a bitter and astringent taste, but all the panelists scored both curries higher than 7 out of 9, confirming their acceptable flavor. Results suggest that the Massaman and spicy basil leaves contain various phytochemicals at different levels and may be further used as functional ingredients and nutraceutical products.

Theoretical insight of reactive oxygen species scavenging mechanism in lignin waste depolymerization products

Apart from natural products and synthesis, phenolic compounds can be produced from the depolymerization of lignin, a major waste in biofuel and paper production. This process yields a plethora of aryl propanoid phenolic derivatives with broad biological activities, especially antioxidant properties. Due to its versatility, our study focuses on investigating the antioxidant mechanisms of several phenolic compounds obtained from renewable and abundant resources, namely, syringol (Hs), 4-allylsyringol (HAs), 4-propenylsyringol (HPns), and 4-propylsyringol (HPs). Employing the density functional theory (DFT) approach in conjunction with the QM-ORSA protocol, we aim to explore the reactivity of these compounds in neutralizing hydroperoxyl radicals in physiological and non-polar media. Kinetic and thermodynamic parameter calculations on the antioxidant activity of these compounds were also included in this study. Additionally, our research utilizes the activation strain model (ASM) for the first time to explain the reactivity of the HT and RAF mechanisms in the peroxyl radical scavenging process. It is predicted that HPs has the best rate constant in both media (1.13 × 108 M-1 s-1 and 1.75 × 108 M-1 s-1, respectively). Through ASM analysis, it is observed that the increase in the interaction energy due to the formation of intermolecular hydrogen bonds during the reaction is an important feature for accelerating the hydrogen transfer process. Furthermore, by examining the physicochemical and toxicity parameters, only Hs is not suitable for further investigation as a therapeutic agent because of potential toxicity and mutagenicity. However, overall, all compounds are considered potent HOO˙ scavengers in lipid-rich environments compared to previously studied antioxidants.

Inhibitory Effect of Quercetin on Oxidative Endogen Enzymes: A Focus on Putative Binding Modes

Oxidative stress is defined as an imbalance between the production of free radicals and reactive oxygen species (ROS) and the ability of the body to neutralize them by anti-oxidant defense systems. Cells can produce ROS during physiological processes, but excessive ROS can lead to non-specific and irreversible damage to biological molecules, such as DNA, lipids, and proteins. Mitochondria mainly produce endogenous ROS during both physiological and pathological conditions. Enzymes like nicotinamide adenine dinucleotide phosphate oxidase (NOX), xanthine oxidase (XO), lipoxygenase (LOX), myeloperoxidase (MPO), and monoamine oxidase (MAO) contribute to this process. The body has enzymatic and non-enzymatic defense systems to neutralize ROS. The intake of bioactive phenols, like quercetin (Que), can protect against pro-oxidative damage by quenching ROS through a non-enzymatic system. In this study, we evaluate the ability of Que to target endogenous oxidant enzymes involved in ROS production and explore the mechanisms of action underlying its anti-oxidant properties. Que can act as a free radical scavenger by donating electrons through the negative charges in its phenolic and ketone groups. Additionally, it can effectively inhibit the activity of several endogenous oxidative enzymes by binding them with high affinity and specificity. Que had the best molecular docking results with XO, followed by MAO-A, 5-LOX, NOX, and MPO. Que's binding to these enzymes was confirmed by subsequent molecular dynamics, revealing different stability phases depending on the enzyme bound. The 500 ns simulation showed a net evolution of binding for NOX and MPO. These findings suggest that Que has potential as a natural therapy for diseases related to oxidative stress.

Discovery of New Hydrazone-Thiazole Polyphenolic Antioxidants through Computer-Aided Design and In Vitro Experimental Validation

Oxidative stress is linked to a series of diseases; therefore, the development of efficient antioxidants might be beneficial in preventing or ameliorating these conditions. Based on the structure of a previously reported compound with good antioxidant properties and on computational studies, we designed several catechol derivatives with enhanced antioxidant potential. The compounds were synthesized and physicochemically characterized, and their antioxidant activity was assessed through different antiradical, electron transfer and metal ions chelation assays, their electrochemical behavior and cytotoxicity were studied. The results obtained in the in vitro experiments correlated very well with the in silico studies; all final compounds presented very good antioxidant properties, generally superior to those of the reference compounds used. Similarly, the results obtained from studying the compounds' electrochemical behavior were in good agreement with the results of the antioxidant activity evaluation assays. Regarding the compounds' cytotoxicity, compound 7b had a dose-dependent inhibitory effect against all cell lines. In conclusion, through computer-aided design, we developed several catechol thiazolyl-hydrazones with excellent antioxidant properties, of which compound 7b, with two catechol moieties in its structure, exhibited the best antioxidant activity.

Phytofabrication of Selenium Nanoparticles with Moringa oleifera (MO-SeNPs) and Exploring Its Antioxidant and Antidiabetic Potential

The advancement in nanotechnology is the trigger for exploring the synthesis of selenium nanoparticles and their use in biomedicine. Therefore, this study aims to synthesize selenium nanoparticles using M. oleifera as a reducing agent and evaluate their antioxidant and antidiabetic potential. Our result demonstrated a change in the color of the mixture from yellow to red, and UV-Vis spectrometry of the suspension solution confirmed the formation of MO-SeNPs with a single absorbance peak in the range of 240-560 nm wavelength. FTIR analysis revealed several bioactive compounds, such as phenols and amines, that could possibly be responsible for the reduction and stabilization of the MO-SeNPs. FESEM + EDX analysis revealed that the amorphous MO-SeNPs are of high purity, have a spherical shape, and have a size of 20-250 nm in diameter, as determined by HRTEM. MO-SeNPs also exhibit the highest DPPH scavenging activity of 84% at 1000 μg/mL with an IC50 of 454.1 μg/mL and noteworthy reducing ability by reducing power assay. Furthermore, MO-SeNPs showed promising antidiabetic properties with dose-dependent inhibition of α-amylase (26.7% to 44.53%) and α-glucosidase enzyme (4.73% to 19.26%). Hence, these results demonstrated that M. oleifera plant extract possesses the potential to reduce selenium ions to SeNPs under optimized conditions with notable antioxidant and antidiabetic activities.

Antioxidant activity of lidocaine, bupivacaine, and ropivacaine in aqueous and lipophilic environments: an experimental and computational study

Introduction: Local anesthetics are widely recognized pharmaceutical compounds with various clinical effects. Recent research indicates that they positively impact the antioxidant system and they may function as free radical scavengers. We hypothesize that their scavenging activity is influenced by the lipophilicity of the environment. Methods: We assessed the free radical scavenging capacity of three local anesthetics (lidocaine, bupivacaine, and ropivacaine) using ABTS, DPPH, and FRAP antioxidant assays. We also employed quantum chemistry methods to find the most probable reaction mechanism. The experiments were conducted in an aqueous environment simulating extracellular fluid or cytosol, and in a lipophilic environment (n-octanol) simulating cellular membranes or myelin sheets. Results: All local anesthetics demonstrated ABTS˙⁺ radical scavenging activity, with lidocaine being the most effective. Compared to Vitamin C, lidocaine exhibited a 200-fold higher half-maximal inhibitory concentration. The most thermodynamically favorable and only possible reaction mechanism involved hydrogen atom transfer between the free radical and the -C-H vicinal to the carbonyl group. We found that the antioxidant activity of all tested local anesthetics was negligible in lipophilic environments, which was further confirmed by quantum chemical calculations. Conclusion: Local anesthetics exhibit modest free radical scavenging activity in aqueous environments, with lidocaine demonstrating the highest activity. However, their antioxidant activity in lipophilic environments, such as cellular membranes, myelin sheets, and adipose tissue, appears to be negligible. Our results thus show that free radical scavenging activity is influenced by the lipophilicity of the environment.

Interactive network pharmacology and electrochemical analysis reveals electron transport-mediating characteristics of Chinese medicine formula Jing Guan Fang

Background

Jing Guan Fang (JGF) is an anti-COVID-19 Chinese Medicine decoction comprised of five medicinal herbs to possess anti-inflammatory and antiviral properties for treatment. This study aims to electrochemically decipher the anti-coronavirus activity of JGF and show that microbial fuel cells may serve as a platform for screening efficacious herbal medicines and providing scientific bases for the mechanism of action (MOA) of TCMs.

Methods

Electrochemical techniques (e.g., cyclic voltammetry) and MFCs were adopted as the bioenergy-based platforms to assess the bioenergy-stimulating characteristics of JGF. Phytochemical analysis correlated polyphenolic and flavonoid content with antioxidant activity and bioenergy-stimulating properties. Network pharmacology on the active compounds was employed to identify anti-inflammatory and anti-COVID-19 protein targets, and molecular docking validated in silico results.

Significant findings

This first-attempt results show that JGF possesses significant reversible bioenergy-stimulation (amplification 2.02 ± 0.04) properties suggesting that its antiviral efficacy is both bioenergy-steered and electron mediated. Major flavonoids and flavone glycosides identified by HPLC (e.g., baicalein and baicalin, respectively) possess electron-shuttling (ES) characteristics that allow herbal medicines to treat COVID-19 via (1) reversible scavenging of ROS to lessen inflammation; (2) inhibition of viral proteins; and (3) targeting of immunomodulatory pathways to stimulate the immune response according to network pharmacology.

Metabolic Alterations in Streptozotocin-nicotinamide-induced Diabetic Rats Treated with Muntingia calabura Extract via 1H-NMR-based Metabolomics

Diabetes mellitus (DM) is a metabolic endocrine disorder caused by decreased insulin concentration or poor insulin response. Muntingia calabura (MC) has been used traditionally to reduce blood glucose levels. This study aims to support the traditional claim of MC as a functional food and blood-glucose-lowering regimen. The antidiabetic potential of MC is tested on a streptozotocin-nicotinamide (STZ-NA)-induced diabetic rat model by using the ¹H-NMR-based metabolomic approach. Serum biochemical analyses reveal that treatment with 250 mg/kg body weight (bw) standardized freeze-dried (FD) 50% ethanolic MC extract (MCE 250) shows favorable serum creatinine (37.77 ± 3.53 µM), urea (5.98 ± 0.84 mM) and glucose (7.36 ± 0.57 mM) lowering capacity, which was comparable to the standard drug, metformin. The clear separation between diabetic control (DC) and normal group in principal component analysis indicates the successful induction of diabetes in the STZ-NA-induced type 2 diabetic rat model. A total of nine biomarkers, including allantoin, glucose, methylnicotinamide, lactate, hippurate, creatine, dimethylamine, citrate and pyruvate are identified in rats' urinary profile, discriminating DC and normal groups through orthogonal partial least squares-discriminant analysis. Induction of diabetes by STZ-NA is due to alteration in the tricarboxylic acid (TCA) cycle, gluconeogenesis pathway, pyruvate metabolism and nicotinate and nicotinamide metabolism. Oral treatment with MCE 250 in STZ-NA-induced diabetic rats shows improvement in the altered carbohydrate metabolism, cofactor and vitamin metabolic pathway, as well as purine and homocysteine metabolism.

Advances in the study of the function and mechanism of the action of flavonoids in plants under environmental stresses

MAIN CONCLUSION

This review summarizes the anti-stress effects of flavonoids in plants and highlights its role in the regulation of polar auxin transport and free radical scavenging mechanism. As secondary metabolites widely present in plants, flavonoids play a vital function in plant growth, but also in resistance to stresses. This review introduces the classification, structure and synthetic pathways of flavonoids. The effects of flavonoids in plant stress resistance were enumerated, and the mechanism of flavonoids in plant stress resistance was discussed in detail. It is clarified that plants under stress accumulate flavonoids by regulating the expression of flavonoid synthase genes. It was also determined that the synthesized flavonoids are transported in plants through three pathways: membrane transport proteins, vesicles, and bound to glutathione S-transferase (GST). At the same time, the paper explores that flavonoids regulate polar auxin transport (PAT) by acting on the auxin export carrier PIN-FORMED (PIN) in the form of ATP-binding cassette subfamily B/P-glycoprotein (ABCB/PGP) transporter, which can help plants to respond in a more dominant form to stress. We have demonstrated that the number and location of hydroxyl groups in the structure of flavonoids can determine their free radical scavenging ability and also elucidated the mechanism by which flavonoids exert free radical removal in cells. We also identified flavonoids as signaling molecules to promote rhizobial nodulation and colonization of arbuscular mycorrhizal fungi (AMF) to enhance plant-microbial symbiosis in defense to stresses. Given all this knowledge, we can foresee that the in-depth study of flavonoids will be an essential way to reveal plant tolerance and enhance plant stress resistance.

Machine Learning to Predict Homolytic Dissociation Energies of C-H Bonds: Calibration of DFT-based Models with Experimental Data

Random Forest (RF) QSPR models were developed with a data set of homolytic bond dissociation energies (BDE) previously calculated by B3LYP/6-311++G(d,p)//DFTB for 2263 sp3C-H covalent bonds. The best set of attributes consisted in 114 descriptors of the carbon atom (counts of atom types in 5 spheres around the kernel atom and ring descriptors). The optimized model predicted the DFT-calculated BDE of an independent test set of 224 bonds with MAE=2.86 kcal/mol. A new data set of 409 bonds from the iBonD database (http://ibond.nankai.edu.cn) was predicted by the RF with a modest MAE (5.36 kcal/mol) but a relatively high R² (0.75) against experimental energies. A prediction scheme was explored that corrects the RF prediction with the average deviation observed for the k nearest neighbours (KNN) in an additional memory of experimental data. The corrected predictions achieved MAE=2.22 kcal/mol for an independent test set of 145 bonds and the corresponding experimental bond energies.

Antioxidant Activity and Reactive Oxygen Species (ROS) Scavenging Mechanism of Eriodictyon californium, an Edible Herb of North America

Modern life associated with processed food, exposure to a wide range of pollutants, physical inactivity, unprecedented time, excessive involvement of technology in our lives, and so on give rise to oxidative stress which threatens our physical and mental health. Because of rising healthcare costs and mistrust of conventional medicine, mankind is looking for alternatives to over-the-counter medications and prescription drugs, which is driving the demand for nutraceuticals across the globe. Antioxidant-rich plant-based natural products could be an important source of nutraceuticals to boost endogenous antioxidant levels. In this research, we uncovered the antioxidant potential of Eriodictyon californicum, an herb used by Native Americans for centuries to treat a wide range of ailments. The ethanolic leaf extract of E. californicum was studied for its phytochemical constituents, antioxidant potential, and free radical scavenging activity. Phytochemical analysis revealed the presence of flavonoids, saponins, phenols, tannins, terpenoids, cardiac glycosides, and steroids. The abundance of total phenol (78.58 ± 0.016 μg GAE/mg) and flavonoid content (6.76 ± 0.003 μg QE/mg) and the strong reducing activity in the FRAP assay indicated the antioxidant potential of the leaves. Free radical scavenging activity was confirmed by a dose-dependent response on the DPPH assay (IC50 0.071 mg/mL). Since reactive oxygen species are the main culprits for causing oxidative stress in our body, studying the effect of plant extracts on superoxide, hydrogen peroxide, and hydroxyl radicals found that it has the ability to neutralize all three. IC50 was found to be 0.083 mg/mL for superoxide radicals, 0.033 mg/mL for hydrogen peroxide, and 0.080 mg/mL for hydroxyl radicals. Herein, we report that E. californicum is a potential source of bioactive components with strong radical scavenging activity. This holy herb could serve as a healing agent against oxidative stress and holds promise for the development of nutraceuticals.

Thiogenistein-Antioxidant Chemistry, Antitumor Activity, and Structure Elucidation of New Oxidation Products

Isoflavonoids such as genistein (GE) are well known antioxidants. The predictive biological activity of structurally new compounds such as thiogenistein (TGE)–a new analogue of GE–becomes an interesting way to design new drug candidates with promising properties. Two oxidation strategies were used to characterize TGE oxidation products: the first in solution and the second on the 2D surface of the Au electrode as a self-assembling TGE monolayer. The structure elucidation of products generated by different oxidation strategies was performed. The electrospray ionization mass spectrometry (ESI-MS) was used for identifying the product of electrochemical and hydrogen peroxide oxidation in the solution. Fourier transform infrared spectroscopy (FT-IR) with the ATR mode was used to identify a product after hydrogen peroxide treatment of TGE on the 2D surface. The density functional theory was used to support the experimental results for the estimation of antioxidant activity of TGE as well as for the molecular modeling of oxidation products. The biological studies were performed simultaneously to assess the suitability of TGE for antioxidant and antitumor properties. It was found that TGE was characterized by a high cytotoxic activity toward human breast cancer cells. The research was also carried out on mice macrophages, disclosing that TGE neutralized the production of the LPS-induced reactive oxygen species (ROS) and exhibits ABTS (2,2′-azino-bis-3-(ethylbenzothiazoline-6-sulphonic acid) radical scavenging ability. In the presented study, we identified the main oxidation products of TGE generated under different environmental conditions. The electroactive centers of TGE were identified and its oxidation mechanisms were proposed. TGE redox properties can be related to its various pharmacological activities. Our new thiolated analogue of genistein neutralizes the LPS-induced ROS production better than GE. Additionally, TGE shows a high cytotoxic activity against human breast cancer cells. The viability of MCF-7 (estrogen-positive cells) drops two times after a 72-h incubation with 12.5 μM TGE (viability 53.86%) compared to genistein (viability 94.46%).

Flavonoid Profiles and Antioxidant Potential of Monochoria angustifolia (G. X. Wang) Boonkerd & Tungmunnithum, a New Species from the Genus Monochoria C. Presl

Plants of the genus Monochoria have long been utilized in food, cosmetics, and traditional herbal treatments. Thailand has the highest species diversity of this genus and a new member, Monochoria angustifolia (G. X. Wang) Boonkerd & Tungmunnithum has been recently described. This plant is called “Siam Violet Pearl” as a common name or “Khimuk Si Muang Haeng Siam” as its vernacular name with the same meaning in the Thai language. Despite their importance, little research on Monochoria species has been conducted. This study, thus, provides the results to fill in this gap by: (i) determining flavonoid phytochemical profiles of 25 natural populations of M. angustifolia covering the whole floristic regions in Thailand, and (ii) determining antioxidant activity using various antioxidant assays to investigate probable mechanisms. The results revealed that M. angustifolia presents a higher flavonoid content than the outgroup, M. hastata. Our results also revealed that flavonoids might be used to investigate Monochoria evolutionary connections and for botanical authentication. The various antioxidant assays revealed that M. angustifolia extracts preferentially act through a hydrogen atom transfer antioxidant mechanism. Pearson correlation analysis indicated significant correlations, emphasizing that the antioxidant capacity is most probably due to the complex action of several phytochemicals rather than that of a single molecule. Together, these results showed that this new species provide an attractive alternative starting material with phytochemical variety and antioxidant potential for the phytopharmaceutical industry.

Mitoprotective Effects of a Synergistic Nutraceutical Combination: Basis for a Prevention Strategy Against Alzheimer’s Disease

Evidence to date suggests the consumption of food rich in bioactive compounds, such as polyphenols, flavonoids, omega-3 fatty acids may potentially minimize age-related cognitive decline. For neurodegenerative diseases, such as Alzheimer’s disease (AD), which do not yet have definitive treatments, the focus has shifted toward using alternative approaches, including prevention strategies rather than disease reversal. In this aspect, certain nutraceuticals have become promising compounds due to their neuroprotective properties. Moreover, the multifaceted AD pathophysiology encourages the use of multiple bioactive components that may be synergistic in their protective roles when combined. The objective of the present study was to determine mechanisms of action underlying the inhibition of Aβ_1–42-induced toxicity by a previously determined, three-compound nutraceutical combination D₅L₅U₅ for AD. In vitro experiments were carried out in human neuroblastoma BE(2)-M17 cells for levels of ROS, ATP mitophagy, and mitobiogenesis. The component compounds luteolin (LUT), DHA, and urolithin A (UA) were independently protective of mitochondria; however, the D₅L₅U₅ preceded its single constituents in all assays used. Overall, it indicated that D₅L₅U₅ had potent inhibitory effects against Aβ_1–42-induced toxicity through protecting mitochondria. These mitoprotective activities included minimizing oxidative stress, increasing ATP and inducing mitophagy and mitobiogenesis. However, this synergistic nutraceutical combination warrants further investigations in other in vitro and in vivo AD models to confirm its potential to be used as a preventative therapy for AD.

Phytochemical Diversity and Antioxidant Potential of Natural Populations of Nelumbo nucifera Gaertn. throughout the Floristic Regions in Thailand

Asian lotus has long been consumed as a food and herbal drug that provides several health benefits. The number of studies on its biological activity is significant, but research at the population level to investigate the variation in phytochemicals and biological activity of each population which is useful for a more efficient phytopharmaceutical application strategy remains needed. This present study provided the frontier results to fill-in this necessary gap to investigating the phytopharmaceutical potential of perianth and stamen, which represent an important part for Asian traditional medicines, from 18 natural populations throughout Thailand by (1) determining their phytochemical profiles, such as total contents of phenolic, flavonoid, and anthocyanin, and (2) determining the antioxidant activity of these natural populations using various antioxidant assays to examine different mechanisms. The result showed that Central is the most abundant floristic region. The stamen was higher in total phenolic and flavonoid contents, whereas perianth was higher in monomeric anthocyanin content. This study provided the first description of the significant correlation between phytochemical contents in perianth compared with stamen extracts, and indicated that flavonoids are the main phytochemical class. This analysis indicated that the stamen is a richer source of flavonoids than perianth, and provided the first report to quantify different flavonoids accumulated in stamen and perianth extracts under their native glycosidic forms at the population level. Various antioxidant assays revealed that major flavonoids from N. nucifera prefer the hydrogen atom transfer mechanism when quenching free radicals. The significant correlations between various phytochemical classes and the different antioxidant tests were noted by Pearson correlation coefficients and emphasized that the antioxidant capability of an extract is generally the result of complex phytochemical combinations as opposed to a single molecule. These current findings offer the alternative starting materials to assess the phytochemical diversity and antioxidant potential of N. nucifera for phytopharmaceutical sectors.

Phytochemical Profile, Free Radical Scavenging and Anti-Inflammatory Properties of Acalypha Indica Root Extract: Evidence from In Vitro and In Vivo Studies

In our in vitro and in vivo studies, we used Acalypha indica root methanolic extract (AIRME), and investigated their free radical scavenging/antioxidant and anti-inflammatory properties. Primarily, phytochemical analysis showed rich content of phenols (70.92 mg of gallic acid/g) and flavonoids (16.01 mg of rutin/g) in AIRME. We then performed HR-LC-MS and GC-MS analyses, and identified 101 and 14 phytochemical compounds, respectively. Among them, ramipril glucuronide (1.563%), antimycin A (1.324%), swietenine (1.134%), quinone (1.152%), oxprenolol (1.118%), choline (0.847%), bumetanide (0.847%) and fenofibrate (0.711%) are the predominant phytomolecules. Evidence from in vitro studies revealed that AIRME scavenges DPPH and hydroxyl radicals in a concentration dependent manner (10–50 μg/mL). Similarly, hydrogen peroxide and lipid peroxidation were also remarkably inhibited by AIRME as concentration increases (20–100 μg/mL). In vitro antioxidant activity of AIRME was comparable to ascorbic acid treatment. For in vivo studies, carrageenan (1%, sub-plantar) was injected to rats to induce localized inflammation. Acute inflammation was represented by paw-edema, and significantly elevated (p < 0.05) WBC, platelets and C-reactive protein (CRP). However, AIRME pretreatment (150/300 mg/kg bodyweight) significantly (p < 0.05) decreased edema volume. This was accompanied by a significant (p < 0.05) reduction of WBC, platelets and CRP with both doses of AIRME. The decreased activities of superoxide dismutase, catalase, glutathione reductase and glutathione peroxidase in paw tissue were restored (p < 0.05 / p < 0.01) with AIRME in a dose-dependent manner. Furthermore, AIRME attenuated carrageenan-induced neutrophil infiltrations and vascular dilation in paw tissue. For the first time, our findings demonstrated the potent antioxidant and anti-inflammatory properties of AIRME, which could be considered to develop novel anti-inflammatory drugs.

The Anticancer Potential of Apigenin Via Immunoregulation

Apigenin is an edible flavonoid widely distributed in natural plants, including most vegetables and fruits. Previous studies have revealed that apigenin possesses multiple biological functions by demonstrating antiinflammatory, anti-oxidative, anti-bacterial, anti-viral, anti-tumor and cardiovascular protective effects. Furthermore, recent progressions have disclosed a novel perspective of the anti-cancer roles of apigenin through its immunoregulatory functions. With the rapid progression of the groundbreaking strategies being developed for cancer immunotherapy, its immunoregulatory roles are being recognized as intriguing features of the multifaceted apigenin. However, the current understanding of this emerging role of apigenin still remains limited. Therefore, in the present review, recent advances on the immunoregulatory properties of apigenin in various diseases with a special focus on neoplasm, are summarized. Clinical strategies of cancer immunotherapy are briefly introduced and findings on apigenin linked to immunoregulatory roles in immunotherapy-associated aspects are brought together. The bioactivity, bioavailability, toxicity and potential of apigenin, to be considered as a therapeutic agent in anti-tumor immunotherapy, is discussed. Disclosed molecular mechanisms underlying the immunoregulatory roles of apigenin in cancer immunotherapy are also summarized. Based on findings from the literature, apigenin has the potential to serve as a prospective adjuvant for anti-cancer immunotherapy and warrants further investigations.

Analysis of Conformational, Structural, Magnetic, and Electronic Properties Related to Antioxidant Activity: Revisiting Flavan, Anthocyanidin, Flavanone, Flavonol, Isoflavone, Flavone, and Flavan-3-ol

Understanding the antioxidant activity of flavonoids is important to investigate their biological activities as well as to design novel molecules with low toxicity and high activity. Aromaticity is a chemical property found in cyclic structures that plays an important role in their stability and reactivity, and its investigation can help us to understand the antioxidant activity of some heterocyclic compounds. In the present study, we applied the density functional theory (DFT) to investigate the properties of seven flavonoid structures with well-reported antioxidant activity: flavan, anthocyanidin, flavanone, flavonol, isoflavone, flavone, and flavan-3-ol. Conformational, structural, magnetic, and electronic analyses were performed using nuclear magnetic resonance, ionization potentials, electron affinity, bond dissociation energy, proton affinity, frontier molecular orbitals (highest occupied molecular orbital (HOMO)/lowest unoccupied molecular orbital (LUMO)), and aromaticity through nucleus-independent chemical shifts to analyze these seven flavonoid structures. We revised the influence of hydroxyl groups on the properties of flavonoids and also investigated the influence of the aromaticity of these seven flavonoids on the antioxidant activity.

Antioxidant Behavior Affected by Polarity in the Olive Oil: Experimental and Molecular Simulation Investigations

Natural antioxidants are essential potential sources for protecting the oxidation of food oils. However, until now, the mechanisms are still not very clear, especially from the quantitatively theoretical level to analyze the antioxidant behavior. In this work, the micromechanisms of the antioxidant behavior affected by polarity in the olive oil were systematically investigated by experimental and computational methods. The results showed that the polarity of antioxidants decreased with the growth of the alkyl chains, which had multiple impacts on the effectiveness of antioxidants. The excessive polarity gap between the antioxidant and oil molecules would cause the antioxidant to be dispersed at the oil-air interface, which could enhance their antioxidant ability. Meanwhile, the antioxidants with longer alkyl chains had lower polarity and better dispersibility but decreased mobility. Hence, compared with other antioxidants, medium polarity antioxidants presented both good dispersion and relatively suitable migration, indicating that they would have an optimal antioxidant effect.

Mutational spectra induced by flavonoid extracts from pepper tree (Schinus terebinthifolius, Raddi) stem bark

Flavonoids are a diverse family of plant compounds that are involved in pigmentation, protection, and endogenous regulation. Flavonoids also have medicinal applications, suggesting that they may exert chemoprotective effects. However, some studies have shown, that some plant flavonoids have oxidative and toxic effects, including those produced by Schinus terebinthifolius. In Brazil, extracts of this plant are widely used for medical purposes. In this study, we analyzed the mutagenic potential of two flavonoid-enriched fractions from Brazilian pepper tree stem bark using Escherichia coli CC strains deficient and proficient in enzymes involved in the DNA repair of oxidative lesions. The highest mutagenic response was detected in the CC104mutMmutY strain but CC104mutY showed a higher mutation frequency than CC104mutM. The spectrum of mutations induced in plasmid DNA is composed of mutations typically caused by oxidative lesions. However, a new type of lesion must be occurred to explain the cytotoxicity, higher mutation rates in the CC104mutY strain, and the rare A:T → T:A and G:C → C:G transversions found in this work.

Impact of the phenolic O–H vs. C-ring C–H bond cleavage on the antioxidant potency of dihydrokaempferol

In order to correctly estimate hydrogen atom abstraction from polyphenols, kinetic analysis including suitable tunneling effects should be mandatory.

The Effect of Sacred Lotus (Nelumbo nucifera) and Its Mixtures on Phenolic Profiles, Antioxidant Activities, and Inhibitions of the Key Enzymes Relevant to Alzheimer's Disease

Sacred lotus (Nelumbo nucifera) has long been used as a food source and ingredient for traditional herbal remedies. Plant parts contain neuroprotective agents that interact with specific targets to inhibit Alzheimer's disease (AD). Organic solvents including methanol, ethyl acetate, hexane, and n-butanol, are widely employed for extraction of sacred lotus but impact food safety. Seed embryo, flower stalk, stamen, old leaf, petal, and leaf stalk of sacred lotus were extracted using hot water (aqueous extraction). The extractions were analyzed for their bioactive constituents, antioxidant and anti-AD properties as key enzyme inhibitory activities toward acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and β-secretase 1 (BACE-1). Results showed that the sacred lotus stamen exhibited significant amounts of phenolics, including phenolic acids and flavonoids, that contributed to high antioxidant activity via both single electron transfer (SET) and hydrogen atom transfer (HAT) mechanisms, with anti-AChE, anti-BChE, and anti-BACE-1 activities. To enhance utilization of other sacred lotus parts, a combination of stamen, old leaf and petal as the three sacred lotus plant components with the highest phenolic contents, antioxidant activities, and enzyme inhibitory properties was analyzed. Antagonist interaction was observed, possibly from flavonoids-flavonoids interaction. Further in-depth elucidation of this issue is required. Findings demonstrated that an aqueous extract of the stamen has potential for application as a functional food to mitigate the onset of Alzheimer's disease.

Theoretical Study on the Antioxidant Activity of Natural Depsidones

Depsidones are secondary metabolites in lichens with a range of potential health benefits. Among others, these compounds are believed to exhibit high hydroxyl radical and superoxide scavenging abilities, warranting a detailed investigation of their antioxidant properties. In this study, the radical scavenging activity of natural depsidones from Ramalina lichenized fungi was investigated in silico. Calculations of the thermodynamic parameters suggested that the main radical scavenging pathway follows the formal hydrogen transfer (FHT) mechanism; however, unexpectedly low rate constants were found in the CH3OO• scavenging reaction. Establishing that the depsidones are mostly ionized in an aqueous environment suggested that the single-electron transfer (SET) mechanism should not be ruled out. Consistently, depsidones were revealed to be excellent HO• and O2 •- scavengers in aqueous solutions (k = 4.60 × 105 - 8.60 × 109 M-1 s-1 and k = 2.60 × 108 - 8.30 × 109 M-1 s-1, respectively) following the sequential proton loss electron transfer (SPLET) mechanism. These results suggest that natural fungal depsidones are potent hydroxyl and superoxide radical scavengers in aqueous solutions.

Substitution effects on the antiradical activity of hydralazine: a DFT analysis

The antioxidant activity of hydralazine derivatives in the gas-phase and in physiological environments were examined by thermodynamic and kinetic calculations.

Radical Scavenging Activity of Puerarin: A Theoretical Study

Puerarin is a C-glycoside of daidzein, one of the major bioactive ingredients isolated from the root of Pueraria lobata, which has a wide spectrum of pharmacological effects. Although puerarin is well-known for its effective antioxidant activity, there is seldom a systematic theoretical study on its radical scavenging activity. Herein, the free radical scavenging ability of puerarin was investigated systematically by density functional theory (DFT) calculations. The reaction activity was compared with daidzein as well. Three reaction pathways: hydrogen atom transfer (HAT), single electron transfer followed by proton transfer (SET-PT), and sequential proton loss electron transfer (SPLET) were discussed and compared by thermodynamic parameters such as bond dissociation enthalpy (BDE), ionization potential (IP), proton dissociation enthalpy (PDE), proton affinity (PA), and electron transfer enthalpy (ETE). The reaction kinetics of puerarin with special radicals •OH and •OOH were also studied. The results obtained may be of great significance for better understanding the relationship between the antioxidant properties and structural design of puerarin, as well as other antioxidants.

Hydroxyl Radical Scavenging of Indole-3-Carbinol: A Mechanistic and Kinetic Study

Indole-3-carbinol (I3C) is the product of the enzymatic hydrolysis of glucobrassicin in the human body. I3C exhibits diverse bioactivities. It is used as a supplement to enhance the efficiency of some cancer therapies and is available as an over-the-counter dietary supplement described as a potential antioxidant, among other health benefits. Thus, it is important to develop an in-depth understanding of its antioxidant activity. In this study, the hydroxyl radical scavenging of I3C has been investigated in silico under physiologically relevant conditions (aqueous and lipid-mimetic pentyl ethanoate environment) using thermochemical and kinetic calculations. For benchmarking purposes, the results were compared to known experimental data. The overall reaction rate constant of the HO^• radical scavenging of I3C in water was found to be 2.30 × 10¹⁰ M^-1 s^-1 and over two times lower in lipid-mimetic pentyl ethanoate solvent at 7.74 × 10⁹ M^-1 s^-1. The results also highlighted that the HO^• radical scavenging follows almost exclusively the radical adduct formation mechanism (>94%) in a lipid mimetic medium, whereas this mechanism contributes about 60% in aqueous environments. I3C is considered a dopamine-like antioxidant, its main function being prevention of oxidative degradation of lipids; our study supports this view.

Theoretical Study for Exploring the Diglycoside Substituent Effect on the Antioxidative Capability of Isorhamnetin Extracted from Anoectochilus roxburghii

Radical-scavenging activity of isorhamnetin (1) and its diglycosides, named isorhamnetin-3,5'-O-β-D-diglucoside (2) and isorhamnetin-3,7-O-β-D-diglucoside (3) extracted from Anoectochilus roxburghii, has been studied through three main antioxidant pathways: hydrogen atom transfer (HAT), single electron transfer followed by proton transfer, and sequential proton loss electron transfer (SPLET). All thermodynamic parameters related to these radical-scavenging mechanisms were computed at the B3LYP/6-311G(d,p) level of theory both in the gas phase and in solution. The results suggest that HAT is the predominant mechanism in the gas phase, while SPLET is supported in an aqueous environment. In addition, the stability of radicals has also been explored by electron spin density and intramolecular hydrogen bonding. The potential energy profiles and kinetic calculations for the reactions between the selected compounds and the CH₃OO^• radical were calculated at 298.15 K. Among all investigated, compound 2 has the highest antioxidant activity with the lowest Gibbs free energy (-4.05 kcal/mol) and the highest hydrogen atom transfer rate constant (3.61 × 10⁵ M^-1 s^-1). Substitution of the OH and OMe groups by two glucoses at the 3 and 5' sites of isorhamnetin has a significant impact on its antioxidant activity.

Is Indolinonic Hydroxylamine a Promising Artificial Antioxidant?

Indolinonic hydroxylamine (IH) is a new-generation artificial antioxidant that, due to its ability to fractionate into apolar environments, is considered for prevention against lipid peroxidation. For this reason, it is important to understand, and compare, its activity in polar and nonpolar environments. In this study, the antioxidant activity of IH has been evaluated against HO^• and HOO^• radicals in water and, for a lipid-mimetic environment, pentyl ethanoate solvent, using kinetic calculations. It was found that the overall reaction rate constant of the HO^• radical scavenging is more than 7 times higher in aqueous (8.98 × 10⁹ M^-1 s^-1) than in apolar (1.22 × 10⁹ M^-1 s^-1) media. However, HOO^• scavenging was 35 times faster in apolar media (1.00 × 10⁵ M^-1 s^-1 vs 2.80 × 10³ M^-1 s^-1). In a lipid environment, the HAT mechanism was favored for the antioxidant activity for both radical species, whereas in aqueous solution the SET mechanism defined the HO^• scavenging, while HAT described the HOO^• scavenging. IH was shown to be one of the most active antioxidants in lipid environment, an essential characteristic for the protection of biological systems.

A theoretical study of the radical scavenging activity of natural stilbenes

Oxidative stress is implicated in aging and aging-related diseases, including cancer.