Flavonoid Antioxidant Activity Research Articles

Extraction, Composition, and Antioxidant Activity of Flavonoids from Xanthoceras sorbifolium Bunge Leaves.

Xanthoceras sorbifolium Bunge leaves (XLs) are valuable resources rich in phytochemicals, especially in flavonoids, but they are rarely exploited and utilized. The purpose of this paper is to reduce the waste of XLs resources (usually used as agricultural waste) and extract the high added value of active ingredients from XLs. The extraction of flavonoids from XLs using ultrasonic-assisted extraction (UAE) was reported. Response surface methodology (RSM) was used to adopt different ultrasonic conditions such as ethanol concentration, liquid:solid ratio, and ultrasonic power. In addition, the chemical structures were identified using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) and HPLC. Response surface analysis indicated the optimal level of ethanol concentration, liquid:solid ratio, and ultrasonic power as 71.49%, 13.87 mL/g, and 157.49 W respectively for the maximum response of total flavonoids (5.52 ± 0.23%), which fitted well with the predicted value (5.68 ± 0.17%). In addition, the extracts from XLs exhibited potent antioxidant activity using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) ammonium salt (ABTS). The potent antioxidant activity of flavonoids from XLs is beneficial for their application in the food and drug industry, which will facilitate the rise of the added value of the flavonoids from XLs. Myricetin, rutin, and epicatechin, which may be responsible for the antioxidant activity of the extracts from XLs, were confirmed by UPLC-MS/MS and HPLC analysis. The extracted flavonoids can be used as a natural antioxidant additive to food products.

A study from structural insight to the antiamyloidogenic and antioxidant activities of flavonoids: scaffold for future therapeutics of Alzheimer’s disease

A study from structural insight to the antiamyloidogenic and antioxidant activities of flavonoids: scaffold for future therapeutics of Alzheimer’s disease

Protective Effect of Flavonoids from Mulberry Leaf on AAPH-Induced Oxidative Damage in Sheep Erythrocytes.

To evaluate the antioxidant activity of flavonoids extracted from Chinese herb mulberry leaves (ML), flavonoids from mulberry leaves (FML) were extracted and purified by using ultrasonic-assisted enzymatic extraction and D101 macroporous resin. Using LC-MS/MS-Liquid Chromatography with tandem mass spectrometry analysis, hesperidin, rutoside, hyperoside, cyanidin-3-o-glucoside, myricitrin, cyanidin, and quercetin were identified, and NMR and UV were consistent with the verification of IR flavonoid characteristics. The antioxidant activity of FML has also been evaluated as well as the protective effect on 2,2 0-azobis (2-amidinopropane) dihydrochloride (AAPH)-induced oxidative stress. The results showed that FML exhibited powerful antioxidant activity. Moreover, FML showed dose-dependent protection against AAPH-induced sheep erythrocytes' oxidative hemolysis. In the enzymatic antioxidant system, pretreatment with high FML maintained the balance of SOD, CAT, and GSH-Px; in the non-enzymatic antioxidant system, the content of MDA can be effectively reduced after FML treatment. This study provides a research basis for the development of natural products from mulberry leaves.

Different Effects of Quercetin Glycosides and Quercetin on Kidney Mitochondrial Function-Uncoupling, Cytochrome C Reducing and Antioxidant Activity.

Flavonols are found in plants as aglycones and as glycosides. Antioxidant activity of flavonols may occur via several mechanisms within the cell, and mitochondria as a target may play an important role. There is a lack of information about the influence of the sugar moiety on biological activity of flavonoid glycosides. The aims of study were to investigate the effects of quercetin and its glycosides on mitochondrial respiration rates at various metabolic states, and to evaluate their antioxidant potential using chemical and biological approaches. Mitochondrial function was measured using an oxygraphic method, cytochrome c reduction spectrophotometrically, H2O2 generation in mitochondria fluorimetrically, and antioxidant activity of flavonoids using an HPLC-post column system. Our data revealed that quercetin and its glycosides isoquercitrin, rutin, and hyperoside uncouple kidney mitochondrial respiration (increasing the State 2 respiration rate) and significantly reduce cytochrome c. Moreover, quercetin, and its glycosides decrease the production of mitochondrial H2O2 and possess radical scavenging and ferric reducing capacities. The highest activity was characteristic for quercetin, showing that the sugar moiety significantly diminishes its activity. In conclusion, our results show the efficient radical scavenging, ferric and cytochrome c reducing capacities, and uncoupling properties of quercetin and its glycosides, as well as the importance of the sugar residue and its structure in the regulation of kidney mitochondrial function.

Effects of Extraction Technique on the Content and Antioxidant Activity of Flavonoids from Gossypium Hirsutum linn. Flowers

Cotton is one of the Uyghur medical materials in China and is rich in flavonoids. Flavonoids have important pharmacological effects. The yield of flavonoids in traditional extraction methods is low, which affects the development of flavonoids. Therefore, it is urgent to optimize the extraction techniques. The yield of flavonoids in cotton flowers was effectively improved by response surface methodology, and the highest yield of flavonoids reached 5.66%, and the optimal extraction process conditions were obtained. The DPPH free radical scavenging rate, hydroxyl free radical scavenging rate, superoxide anion free radical scavenging rate, and reducing ability were tested to reflect the antioxidant capacity of flavonoids. The flavonoids had an excellent antioxidant effect. Cell experiments suggested that the flavonoids had the effect of protecting glutamate-induced damage to HT-22 cells. The results of this study provide a theoretical basis for the extraction of cotton flowers flavonoids and the comprehensive evaluation of antioxidant products, as well as the extraction of other plant flavonoids.

Photocatalysis of environmental organic pollutants and antioxidant activity of flavonoid conjugated gold nanoparticles

The unique properties of nanomaterials have the potential application in different fields of biomedical application along with the management of environmental pollutants. This research work involved the isolation of hesperidin from the orange peel and the preparation of hesperidin gold nanoparticles by the chemical reduction method. The high substrate specificity and lower band gap enable the excitation of gold nanoparticles in visible light. Hence gold nanoparticles are chosen nowadays for the management and removal of organic pollutants. The efficacy of hesperidin gold nanoparticles was evaluated by the photocatalytic activity on organic dyes and pollutants like methyl orange, methylene blue, bromocresol green, and 4 – nitro phenol with sodium borohydride as reducing agent and the antioxidant study by scavenging of free radicals of DPPH, ABTS, and hydroxyl free radicals of hydrogen peroxide. The kinetics of photocatalytic degradation of organic dyes and 4 – nitro phenol was found to follow the first order with rate constants of 10 × 10−3, 37 × 10−3, 23 × 10−3 and 49 × 10−3 min−1 for methyl orange, methylene blue, bromocresol green and 4 – nitro phenol respectively. The hesperidin gold nanoparticles showed significant antioxidant activity as compared to ascorbic acid as standard. The flavonoid conjugated gold nanoparticles can be an efficient antioxidant and photocatalyst for the management of different diseases and wastewater treatment respectively.

Plant Flavonoids as Potential Natural Antioxidants in Phytocosmetics

Phytocosmetics, the sub-discipline of cosmetology which primarily uses plant and plant extracts in beauty treatments, has been endorsed for thousands of years. After a period of time being pushed aside by an enormous wave of interest in synthetic products, phytocosmetics is slowly but surely returning to its propitious moment. Botanical compounds, among which flavonoids are highlighted, are being recognized for their biological activities – namely antioxidant, anti-aging, anti-inflammatory, anti-microbial and photoprotective activities. The purpose of this paper is to review updates in the extensive research into the potential of flavonoids in cosmetic applications, in order to demonstrate the newest achievement and encourage more interest into the field. A literature search was performed in PubMed in February and March 2022 with key terms including “phytocosmetics”, “flavonoids” and “antioxidant”. To keep the search topical, the publication years were limited to after 2010. The results were screened with the exclusion criteria of duplicate papers, irrelevant research, and non-English articles. The antioxidant activity of flavonoids have been widely established in a variety of plant sources. Their potential in cosmetics is also evident and has been attributed to their chemical structures, with their biological mechanisms starting to be better understood. In conclusion, flavonoids have been shown to be a viable alternative to synthetic antioxidants for cosmetic applications. However, there is still a need to evaluate effective delivery aids and formulations.

Isolation and Characterization of Flavonoids from Fermented Dandelion (Taraxacum mongolicum Hand.-Mazz.), and Assessment of Its Antioxidant Actions In Vitro and In Vivo

Flavonoids are famous for their diverse sources, strong biological activity, and low toxicity and could be used as a natural antioxidant in animal husbandry. In this study, the purification process and antioxidant activity of flavonoids from fermented dandelion were investigated. The adsorption and desorption characterizations of AB-8 macroporous resin for flavonoids from fermented dandelion (FD) were determined and purification parameters were optimized. Qualitative analysis using UPLC-MS/MS analysis was explored to identify the components of the purified flavonoids of FD (PFDF). The antioxidant activity of PFDF in vitro and in vivo was analyzed. The optimum purification parameters were as follows: a sample concentration of 2 mg/mL, 120 mL of the sample volume, a pH of 2.0, and eluted with 90 mL of 70% ethanol (pH 5). After purification, the concentration of the flavonoids in PFDF was 356.08 mg/mL. By comparison with reference standards or the literature data, 135 kinds of flavonoids in PFDF were identified. Furthermore, PFDF had a strong reducing power and scavenging ability against 8-hydroxy radical and DPPH radical. PFDF can effectively reduce the oxidative stress of zebrafish embryos and IPCE-J2 cells by modulating antioxidant enzyme activities. In summary, the purified flavonoids from fermented dandelion have good antioxidant activity and display superior potential as a natural antioxidant in animal husbandry.

Quercetin binding accelerates prion fibrillation into proteinase sensitive and loosely structured amyloids

Amyloidoses are caused by the deposition of amyloid fibrils ascribed to protein misfolding. In this study, we examined the antiamyloidogenic and antioxidative activities of quercetin, a plant flavonol from the flavonoid group of polyphenols, on mouse prion protein (moPrP) with biophysical approaches. As the results show, quercetin binds to the C-terminal region of moPrP, and quercetin binding does not affect the structure of moPrP. However, quercetin binding accelerates moPrP fibrillation and changes the structure of moPrP fibrils. Unlike typical prion fibrils, quercetin-bound fibrils are sensitive to proteinase K and are loosely structured. Moreover, due to high antioxidant activity of flavonoid, quercetin-bound fibrils lack imbalance of free radicals and, therefore, they are nontoxic towards neuroblastoma cells. The quercetin shows its uniqueness from typical antiamyloidogenic drugs which either suppress the development of amyloid or eliminate formed amyloids. Quercetin binding converts moPrP into protease-sensitive and non-cytotoxic fibrils. This work provides a powerful resolution in the advancement of antiamyloidogenic treatment.

Study on Extraction and Antioxidant Activity of Flavonoids from Hemerocallis fulva (Daylily) Leaves.

Hemerocallis fulva is a medical and edible plant. In this study, we optimized the ultrasound-assisted extraction (UAE) process of extracting flavonoids from Hemerocallis fulva leaves by single-factor experiments and response surface methodology (RSM). The optimum extraction conditions generating the maximal total flavonoids content was as follows: 70.6% ethanol concentration; 43.9:1 mL/g solvent to sample ratio; 61.7 °C extraction temperature. Under the optimized extraction conditions, the total flavonoid content (TFC) in eight Hemerocallis fulva varieties were determined, and H. fulva (L.) L. var. kwanso Regel had the highest TFC. The cytotoxicity of the extract was studied using the Cell Counting Kit-8 (CCK-8 assay). When the concentration was less than 1.25 mg/mL, the extract had no significant cytotoxicity to HaCaT cells. The antioxidant activity was measured via chemical antioxidant activity methods in vitro and via cellular antioxidant activity methods. The results indicated that the extract had a strong ABTS and •OH radical scavenging activity. Additionally, the extract had an excellent protective effect against H2O2-induced oxidative damage at a concentration of 1.25 mg/mL, which could effectively reduce the level of ROS to 106.681 ± 9.733% (p < 0.001), compared with the 163.995 ± 6.308% of the H2O2 group. We identified five flavonoids in the extracts using high-performance liquid chromatography (HPLC). Infrared spectroscopy indicated that the extract contained the structure of flavonoids. The results showed that the extract of Hemerocallis fulva leaves had excellent biocompatibility and antioxidant activity, and could be used as a cheap and potential source of antioxidants in the food, cosmetics, and medicine industries.

Interaction Mechanism between OVA and Flavonoids with Different Hydroxyl Groups on B-Ring and Effect on Antioxidant Activity.

Ovalbumin (OVA) is a common carrier with high efficiency to deliver flavonoids. The aim of this study was to investigate the interaction mechanism of OVA and four flavonoids (quercetin (Que), myricetin (Myri), isorhamnetin (Ish), and kaempferol (Kaem)) with similar structures by fluorescence spectra, SDS−PAGE, FT−IR, and molecular docking analysis, and the effect on the antioxidant abilities of flavonoids was also evaluated. Results indicated that the antioxidant activity of flavonoids was positively correlated to the number of phenolic hydroxyl groups of on the B-ring, and weakened when the C-3′ position was replaced by a methoxy group. The addition of OVA enhanced the antioxidant activity of Que/Kaem, while it masked the antioxidant activity of Myri. The formation of Que/Myri/Ish/Kaem−OVA complexes was a spontaneous exothermic process driven mainly by hydrogen bond and van der Waals force, which could result in the change in OVA conformation and induce the transformation of α-helix to β-sheet. Among these, Kaem exhibited the strongest binding ability with OVA, and showed the greatest impact on the secondary and conformational structure of OVA, followed by Que. The hydroxylation of C-3′ and methoxylation of C-5′ weaken the interaction of Kaem with OVA. Molecular docking analysis suggested that Que, Myri, Ish, and Kaem formed six, three, five, and four hydrogen bonds with OVA, and the number of hydrogen bonds was not positively correlated with their binding constants. Our findings can provide a theoretical basis for the application of OVA on improving the antioxidant activity of flavonoids, and may help to explain the delivery efficiency of OVA on different bioactive constituents.

Antibacterial and antioxidant activity of flavonoid, glycoside and alkaloid extracts of Tilia Cordata

About 12,000 chemical compounds isolated from medicinal plants and used to conduct crucial biological functions. These phytochemicals offer long-term health benefits for humans, thus they can be used effectively for treat a variety of human ailments. The goal of this study was to assess the in vitro free radical scavenging and antibacterial activities of glycoside, flavonoid and alkaloid extracts of Tilia cordata plant. According to the findings, flavonoid extract exhibits strong inhibitory action against Staphylococcus aureus but no activity against Escherichia coli. The free radical scavenging activity exhibited that the flavonoid extract was more effective in inhibiting lipid peroxidation more than alkaloid extract, whereas the glycoside extract had no antioxidant activity.

Saponins and flavonoids from Bacopa floribunda plant extract exhibit antioxidant and anti-inflammatory effects on amyloid beta 1-42-induced Alzheimer's disease in BALB/c mice

Ethnopharmacological relevanceBacopa floribunda (BF), a locally available plant has been employed traditionally as memory enhancer in Southwestern, Nigeria. It has been utilized in traditional and Ayurvedic medicine as brain tonic for enhancing memory, anti-aging and forestalling series of psychological disorders. However, there is a dearth of scientific information on the mechanism(s) of action of important phytochemicals from BF extract on dementia. Aim of the studyAlzheimer's disease, the commonest form of dementia has been postulated to triple by 2050 as a result of increase in life expectancy. This study therefore assessed and compared the possible mechanism(s) of action of flavonoids and saponins from BF on Amyloid beta (Aβ1-42)-induced dementia in male BALB/c mice. Materials and methodsEighty (80) healthy BALB/c mice divided into 10 groups (n = 8) were given a single bilateral ICV injection of Aβ1-42 or normal saline. Graded doses of Saponins and flavonoids (50, 100 and 200 mg/kg) were used as treatment for 21 days. Hippocampal homogenates were assayed for the levels of antioxidants, oxidative stress and neuroinflammatory markers. In vitro antioxidant activity of flavonoids and saponins were equally assessed using standard procedures. The extent of microglial activation was quantified through immunohistochemistry procedure. ResultsAβ1-42 successfully caused a spike in hippocampal levels of MDA, IL1β, TNF-α including MPO levels and invariably decreased antioxidant activities. Likewise an increase in reactive microglia (microgliosis) was observed. However, crude saponins and flavonoids from BF were able to suppress microgliosis, oxidative stress and neuroinflammation induced by Aβ1- 42 and were observed to be more effective at higher doses of saponins (100 mg/kg and 200 mg/kg) and flavonoid (100 mg/kg). ConclusionsPhytochemicals from BF efficiently exhibited dose dependent alleviation of some symptoms associated with Alzheimer's disease.

Stability and antioxidant activity of flavonoids from Lycium barbarum L. leaves during digestion in vivo

It has been determined that Lycium barbarum L. leaves are a vital source of bioactive chemicals and have good potential for creating nutritious formulations. In this work, gavage injections of Lycium barbarum L. leaves flavonoids (LBLF) at various doses – 50, 150, and 300 mg/kg BW – were administered to Sprague-Dawley (SD) rats. Four main LBLFs (rutin, chlorogenic acid, kaempferol, and quercetin) were assessed for stability and antioxidant activity in vivo. The findings demonstrated that within 4 h of the LBLF intervention, the plasma levels of rutin, chlorogenic acid, kaempferol, and quercetin were significantly dose-dependent. The rutin content peaked at 762.16 ± 36.63 μg/g at 1 h after the intervention, while the other three peaked at 383.07 ± 3.19 μg/g, 29.44 ± 1.95 μg/g and 18.511 ± 1.99 μg/g, at 3 h after the intervention respectively. Additionally, the levels of malondialdehyde (MDA) were significantly lower, and the activities of glutathione peroxidase (GSH-Px), catalase (CAT), and total superoxide dismutase (T-SOD) were all considerably higher than those of the control group. This will establish a basis for elucidating the LBLF metabolic pathway in vivo, additional research into techniques to increase its stability, and investigation into its therapeutic activity.

Progress in the Electrochemical Analysis of Flavonoids: A Scientometric Analysis in CiteSpace

Background: Flavonoids are a large class of phenolic compounds, which generally refer to two benzene rings (A ring, B ring) with phenolic hydroxyl groups connected to each other through three central carbon atoms, that is, a series of C6-C3-C6 basic core compounds. Because of its potential medicinal value, the research on flavonoids has aroused great interest. Methods: This review aims to identify the research progress and development trends of electrochemical analysis of flavonoids. We retrieved published papers (1998–2020) from Scientific Citation Index Expanded (SCIE) database of the WoS with a topic search related to electrochemical analysis of flavonoids. Results: In this paper, the research progress in electrochemical analysis of flavonoids has been reviewed. Antioxidant activity of flavonoids is the hot area that attracted considerable attention because it directly affects the application of flavonoids. Different analytical methods also received attention of researchers, such as cyclic voltammetry and capillary electrophoresis. This is because advanced analysis technology can be useful for evaluating the property of flavonoids. Conclusion: The research progress and development trends were analyzed based on CiteSpace software of text mining and visualization. Three peaks of this research area can be found as 2004-2005, 2011-2013 and 2016-2018. Although the different countries are conducting research on electrochemical analysis of flavonoids, most of these institutions are not related to each other.

Origin and Function of Structural Diversity in the Plant Specialized Metabolome.

The plant specialized metabolome consists of a multitude of structurally and functionally diverse metabolites, variable from species to species. The specialized metabolites play roles in the response to environmental changes and abiotic or biotic stresses, as well as in plant growth and development. At its basis, the specialized metabolism is built of four major pathways, each starting from a few distinct primary metabolism precursors, and leading to distinct basic carbon skeleton core structures: polyketides and fatty acid derivatives, terpenoids, alkaloids, and phenolics. Structural diversity in specialized metabolism, however, expands exponentially with each subsequent modification. We review here the major sources of structural variety and question if a specific role can be attributed to each distinct structure. We focus on the influences that various core structures and modifications have on flavonoid antioxidant activity and on the diversity generated by oxidative coupling reactions. We suggest that many oxidative coupling products, triggered by initial radical scavenging, may not have a function in se, but could potentially be enzymatically recycled to effective antioxidants. We further discuss the wide structural variety created by multiple decorations (glycosylations, acylations, prenylations), the formation of high-molecular weight conjugates and polyesters, and the plasticity of the specialized metabolism. We draw attention to the need for untargeted methods to identify the complex, multiply decorated and conjugated compounds, in order to study the functioning of the plant specialized metabolome.

Study on the Antioxidant and Anticancer Activities of Sorbus pohuashanensis (Hance) Hedl Flavonoids In Vitro and Its Screen of Small Molecule Active Components

Firstly, the antioxidant capacity of total flavonoids that was extracted from Sorbus pohuashanensis (Hance) Hedl was determined by ABTS+·radical-scavenging method, and MTT assay was used to mensurate the anti-tumor activity of total flavonoids In Vitro. Subsequently, the extraction conditions of flavonoids were optimized by the response surface methodology, the antioxidant activity was investigated simultaneously. Furthermore, the anti-tumor activity mechanism of flavonoids was simulated by molecular docking software. The antioxidant activity of flavonoids was correlated with the content in the process of optimizing the extraction condition. Moreover, The MTT assay revealed that SPF inhibited the activity of four sorts of cancer cells and positively correlated with the concentration of total flavonoids. And the experimental data demonstrated its anticancer activity was better at high concentrations. Finally, its anti-tumor activity was found that may be related to small molecules from flavonoids bind the apoptotic proteins Caspase-3, Caspase-8, and Caspase-9. The study could provide a theoretical basis for further pharmacodynamic research of Sorbus pohuashanensis (Hance) Hedl flavonoids, and improved a valuable attribute to Sorbus pohuashanensis (Hance) Hedl.

Flavonoid Levels and Antioxidant Capacity of Mulberry Leaves: Effects of Growth Period and Drying Methods.

In recent years, various mulberry leaf dishes have gradually gained in popularity. The harvesting period of mulberry leaves and the preparation of dried samples are critical for the retention of flavonoid content and activity. In this study, changes in flavonoid levels in mulberry leaves during their growth period (3–6 months), and the effects of four different drying methods [sun drying (SD), air drying (AD), oven drying (OD), and freeze drying (FD)] on flavonoid accumulation and antioxidant capacity were determined. The results showed that mulberry leaves grown for 6 months had higher levels of flavonoids, and different drying methods could significantly affect the flavonoid levels and antioxidant capacity of the leaves. Air drying and FD were the best methods in terms of retaining the antioxidant activity of flavonoids, although AD had lower operating costs than FD in the production process. Therefore, to obtain a high flavonoid content and maximum antioxidant activity, AD is recommended for mulberry leaves.

Synthesis of Chrysin, Quercetin and Naringin Nitroderivatives: Antiproliferative, Anti-inflammatory and Antioxidant Activity

Background: Flavonoids are an important group of natural products because they possess various biological activities such as antioxidant, anti-inflammatory, and anti-cancer. The modification of their structure could improve their biological activities. The nitro group is included in diverse pharmaceuticals with various biological activities, such as anti-cancer and anti-inflammatory agents. Objective: The study aimed to introduce a nitro group into the structure of flavonoids in order to observe how their anti-proliferative, antioxidant, and anti-inflammatory activities change. Methods: : In this investigation, we established diverse conditions of aromatic nitration of chrysin (1), quercetin (2), and naringin (3) flavonoids using bismuth (III) nitrate, acetic acid or silica gel, and NOx gases. The anti-proliferative activity in CaSki, MDA, and SK-LU-1 cancer cell lines and the anti-inflammatory activity and antioxidant activity of flavonoids and nitro derivatives were evaluated as well. Results: As a result, mild nitration conditions were established, and 8-nitrochrysin, 5’nitroquercetin, and 3’nitronaringin were obtained. The number and hydroxyl group position in the flavonoid are important to carry out the nitration reaction. Although chrysin showed higher anti-proliferative activity than quercetin and naringin, the introduction of the nitro group at C-8 did not improve its antiproliferative, antioxidant, and anti-inflammatory activities. On the other hand, the introduction of the nitro group at C-5̍ in quercetin structure was important to improve its antioxidant and antiproliferative activities on cancer cell lines. The introduction of the nitro group at C-3’ in naringin improved its anti-inflammatory activity, but not its antioxidant and anti-proliferative activities. Chrysin, 8-nitrochrysin, quercetin, and 5’-nitroquercetin did not show necrotic activity. Conclusion: The introduction of a nitro group into flavonoids structure improved their antiproliferative, antioxidant, and anti-inflammatory activities. These results promote future investigations of structural modification on 2-phenylbenzopyran skeleton to optimize their biological activity.

Current State of Knowledge on the Antioxidant Effects and Mechanisms of Action of Polyphenolic Compounds

Quality-of-life improvements have resulted in increasing attention being paid to research on antiaging and antioxidation. Polyphenols are natural antioxidants with excellent biological activities, such as antioxidation and scavenging of free radicals and antiviral activity. Abundant availability and low toxicity of polyphenols have attracted the attention of researchers. In this paper, the antioxidant activities of flavonoids, phenolic acids, stilbenes and lignan polyphenols are analyzed, the corresponding antioxidant mechanisms are investigated, and the antioxidant effects of polyphenols are systematically reviewed. Thus, an effective reference based on the recent literature is compiled for the study of the antioxidant mechanisms of polyphenols that provides a significant theoretical basis for the development of products that are components of polyphenols.