Myricetin inhibits the generation of superoxide anion by reduced form of xanthine oxidase

An Improved Test Method for Assaying the Inhibition of Bioflavonoids on Xanthine Oxidase Activity in vitro

The difference on inhibitory effects of bioflavonoids inhibiting XOD activity assayed by varying test methods cause of us to be further in consideration. The reported test method creating a micro-environment surrounding XOD in the absence of ⋅O2 -, which is seemly different from the assay in vivo. So, the vitro test method for assaying XOD activity is necessary to be improved for selection of potential inhibitors in the presence of ⋅O2 -. The inhibitory results demonstrated that bioflavonoids of MY, DMY, QUE and LUT are capable to be on effective IC50 values, but others are not. As well, their resulting inhibitions determined by the improved test method are much less than that reported in the literature, indicating that their chemical affinities with XOD become weaker. Moreover, DMY assayed on the inhibitions of XOD in the improved test method performs to be a better inhibitor, as compared to the assay of the reported test methods. Abasing on the transformation of DMY into MY in the presence of ⋅O2 -, the good inhibition of DMY on XOD activity can be explained by the synergistic effect of MY.

Inhibition mechanism of fisetin on acetylcholinesterase and its synergistic effect with galantamine

The search for acetylcholinesterase (AChE) inhibitors produced by natural sources is of great significance for the prevention and therapy of Alzheimer's disease and has been widely concerned. In this study, fisetin, a flavonoid compound of plant origin, displayed a mixed inhibition mode on AChE (IC50 = 8.88 ± 0.14 μM). Fluorescence spectra analysis revealed that fisetin statically quenched AChE fluorescence, and the ground state complex was formed by hydrogen bonds and hydrophobic interactions. Circular dichroism assays showed that fisetin induced AChE structure loosened with a decrease in α-helix structure (from 20.6 % to 19.5 %). Computer simulation exhibited that fisetin bound to both the peripheral anionic site (PAS) and the catalytic active site (CAS) and increased the stability of the AChE. Interestingly, the combination of fisetin and galantamine enhanced the binding affinity between AChE and galantamine and induced AChE structure further loosened, while the inhibition mode was still the mixed type. The heatmap analysis indicated that galantamine (0.2 μM) combined with fisetin (2.25 μM) had a significant synergy on AChE inhibition, probably because fisetin binding at the PAS-AChE induced conformation changes of the gorge and CAS, which enhanced galantamine binding affinity with CAS, and a further loose structure of AChE was induced by the mixture, so finally the interaction between the substrate and AChE was strongly affected. This work may offer a theoretical reference for the functional research of fisetin as a potential AChE inhibitor and an enhanced supplement for galantamine.

Ferulic acid ameliorates hyperuricemia by regulating xanthine oxidase

Hyperuricemia is characterized by elevated uric acid (UA) level in the body. The xanthine oxidase (XO) inhibitory ability is an important way to evaluate the anti-hyperuricemia effect of natural products. Ferulic acid (FA) is a phenolic acid compound, and it is a free radical scavenger with many physiological functions. The aim of this study was to investigate the structure-activity relationship, potential mechanism and interaction of FA as XO's inhibitor. In the cell experiment, using 1.25 mM adenosine to incubate for 24 h under the optimal conditions (37 °C, pH = 7.2) can increase the UA production by 1.34 folds. PCR analysis showed that FA could reduce the mRNA expression level of XO. FA inhibited XO in a mixed mode (IC50 = 13.25 μM). The fluorescence quenching of XO by FA occurs through a static mechanism, with an inhibition constant of Ki = 9.527 × 10-5 mol L-1 and an apparent coefficient of α = 1.768. The enthalpy and entropy changes were found as -267.79 KJ mol-1 and - 860.85 KJ mol-1, indicating that both hydrogen binding and hydrophobic are involved in the interaction of this polyphenolic natural compound with XO. Thus, FA supplementation may be a potential therapeutic strategy to improve hyperuricemia by reducing UA production.

Inhibition of toll-like receptor 4 activation by apigenin and chrysin via competition for sites and conformational changes

The activation of toll-like receptor 4 (TLR4) signaling is crucial for initiating and coordinating the immune response against infections, and is proved as a vital target for inflammatory diseases. Herein, TLR4 with sufficient amount and functional activity was generated by heterologous expression and used to investigate the mechanism of apigenin (Api)/chrysin (Chr) inhibition of TLR4 activation. The results demonstrated that Api/Chr exhibited a strong fluorescence quenching effect through a static quenching and a high binding affinity (Ka > 105 L·mol-1) with TLR4, indicating the potential of Api/Chr as a TLR4 inhibitor. Additionally, the binding of Api/Chr induced a loose and unstable conformation of TLR4 with evidence like the decreased hydrophobicity of the tryptophan microenvironment, decreased α-helix content and increased free sulfhydryl content, resulting in reduced stability of the TLR4. The computer simulations revealed that Api/Chr occupied the myeloid differentiation factor 2 (MD-2) binding region, preventing MD-2 from binding to TLR4. Furthermore, the accuracy of the binding site between Api/Chr and TLR4 was confirmed through genetic mutations. Overall, the mechanism by which Api/Chr inhibited TLR4 activation was elucidated at the macroscopic and molecular levels, providing the worthful information concerning the future therapeutic application of Api/Chr as a natural TLR4 inhibitor.

Inhibition of xanthine oxidase-catalyzed xanthine and 6-mercaptopurine oxidation by luteolin, naringenin, myricetin, ampelopsin and their conjugated metabolites

Luteolin, naringenin, myricetin, and ampelopsin are abundant flavonoids in nature, and several dietary supplements also contain them at very high doses. After the peroral intake, flavonoids go through extensive presystemic biotransformation; therefore, typically their sulfate/glucuronic acid conjugates reach high concentrations in the circulation. Xanthine oxidase (XO) enzyme is involved in uric acid production, and it also takes part in the elimination of certain drugs (e.g., 6-mercaptopurine). The inhibitory effects of flavonoid aglycones on XO have been widely studied; however, only limited data are available regarding their sulfate and glucuronic acid conjugates. In this study, we examined the impacts of luteolin, naringenin, myricetin, ampelopsin, and their sulfate/glucuronide derivatives on XO-catalyzed xanthine and 6-mercaptopurine oxidations employing in vitro enzyme incubation assays and molecular modeling studies. Our major results/conclusions are the following: (1) Sulfate metabolites were stronger while glucuronic acid derivatives were weaker inhibitors of XO compared to the parent flavonoids. (2) Naringenin, ampelopsin, and their metabolites were weak inhibitors of the enzyme. (3) Luteolin, myricetin, and their sulfates were highly potent inhibitors of XO, and the glucuronides of luteolin showed moderate inhibitory impacts. (4) Conjugated metabolites of luteolin and myricetin can be involved in the inhibitory effects of these flavonoids on XO enzyme.

Myricetin: a potential plant-derived anticancer bioactive compound-an updated overview

The globe is currently confronting a global fight against the deadliest cancer sickness. Chemotherapy, hormonal therapy, surgery, and radiation therapy are among cancer treatment options. Still, these treatments can induce patient side effects, including recurrence, multidrug resistance, fever, and weakness. As a result, the scientific community is always working on natural phytochemical substances. Numerous phytochemical compounds, including taxol analogues, vinca alkaloids such as vincristine and vinblastine, and podophyllotoxin analogues, are currently undergoing testing and have shown promising results against a number of the deadliest diseases, as well as considerable advantages due to their safety and low cost. According to research, secondary plant metabolites such as myricetin, a flavonoid in berries, herbs, and walnuts, have emerged as valuable bio-agents for cancer prevention. Myricetin and its derivatives have antiinflammatory, anticancer, apoptosis-inducing, and anticarcinogenic properties and can prevent cancer cell proliferation. Multiple studies have found that myricetin has anticancer characteristics in various malignancies, including colon, breast, prostate, bladder, and pancreatic cancers. Current knowledge of the anticancer effects of myricetin reveals its promise as a potentially bioactive chemical produced from plants for the prevention and treatment of cancer. This review aimed to study the numerous bioactivities, mode of action, and modification of several cellular processes that myricetin possesses to impede the spread of cancer cells. This review also addresses the challenges and future prospects of using myricetin as a anticancer drug.

Mining Xanthine Oxidase Inhibitors from an Edible Seaweed Pterocladiella capillacea by Using In Vitro Bioassays, Affinity Ultrafiltration LC-MS/MS, Metabolomics Tools, and In Silico Prediction

The prevalence of gout and the adverse effects of current synthetic anti-gout drugs call for new natural and effective xanthine oxidase (XOD) inhibitors to target this disease. Based on our previous finding that an edible seaweed Pterocladiella capillacea extract inhibits XOD, XOD-inhibitory and anti-inflammatory activities were used to evaluate the anti-gout potential of different P. capillacea extract fractions. Through affinity ultrafiltration coupled with liquid chromatography tandem mass spectrometry (LC-MS/MS), feature-based molecular networking (FBMN), and database mining of multiple natural products, the extract's bioactive components were traced and annotated. Through molecular docking and ADMET analysis, the possibility and drug-likeness of the annotated XOD inhibitors were predicted. The results showed that fractions F4, F6, F4-2, and F4-3 exhibited strong XOD inhibition activity, among which F4-3 reached an inhibition ratio of 77.96% ± 4.91% to XOD at a concentration of 0.14 mg/mL. In addition, the P. capillacea extract and fractions also displayed anti-inflammatory activity. Affinity ultrafiltration LC-MS/MS analysis and molecular networking showed that out of the 20 annotated compounds, 8 compounds have been previously directly or indirectly reported from seaweeds, and 4 compounds have been reported to exhibit anti-gout activity. Molecular docking and ADMET showed that six seaweed-derived compounds can dock with the XOD activity pocket and follow the Lipinski drug-like rule. These results support the value of further investigating P. capillacea as part of the development of anti-gout drugs or related functional foods.

Pleurospermum candollei Methanolic Extract Ameliorates CCl4-Induced Liver Injury by Modulating Oxidative Stress, Inflammatory, and Apoptotic Markers in Rats

The main objective of this study was to investigate the hepatoprotective potency of the Pleurospermum candollei methanol extract against CCl₄-induced liver damage in rats. HPLC technique was used to estimate the presence of polyphenols in the methanol extract of P. candollei (PCM), while proximate analysis revealed the presence of carbohydrates, lipids, and moisture in the extract. The antioxidant potential of PCM was evaluated by 2,2-diphenylpicrylhydrazyl (DPPH) and reducing power assay, which showed a high percentage of inhibition against free radicals. Hepatotoxicity was induced by carbon tetrachloride (CCl₄). CCl₄ administration reduced the activity of endogenous antioxidants, whereas it increased the production of nitrites and hydrogen peroxide (H₂O₂) in rats. Furthermore, the level of hepatic markers in serum was also elevated after CCl₄ administration. Moreover, the expression of stress-related markers, proinflammatory mediators, and apoptotic genes was enhanced in CCl₄-treated rats. Coadministration of PCM along with CCl₄ in rats reduced the levels of free radicals and the above genes to normal levels. CCl₄ administration caused histopathological alterations in liver tissues, while cotreatment with PCM mitigated liver injuries. These findings suggest that the methanol extract of P. candollei possesses antioxidant and anti-inflammatory properties and can prevent liver injury. Further pharmacological research will be helpful in determining the effectiveness of P. candollei in humans. Development of FDA-approved plant-based anti-inflammatory drugs can help treat patients and reduce the chances of toxicity.

Screening and Inhibition Mechanism of Xanthine Oxidase Inhibitors in Ethanolic Extracts of Chimonanthus salicifolius Hu Leaves

This study aimed to evaluate the inhibition of the ethanol elutions of Chimonanthus salicifolius Hu leaves (CsHL) against xanthine oxidase (XO). The results of XO inhibition assay and enzymatic superoxide free radical scavenging assay in vitro showed that 70 % ethanol eluate (EE) had the best inhibitory effect and followed by 40 % EE. High performance liquid chromatograph analysis showed that quercetin and kaempferol were the potential active components of XO inhibition. The inhibition mechanism of quercetin and kaempferol on XO was investigated by kinetic analysis and fluorescence quenching titration assay. The molecular simulation further revealed that quercetin and kaempferol bind to XO mainly by hydrogen bonding and van der Waals, blocking the entry of substrates and leading to the inhibition of XO. In conclusion, the CsHL have inhibitory effects on XO activity, which provides a theoretical basis for relieving or preventing hyperuricemia and gout as a natural food or medicinal plant in the future.

Identification of the Constituents of Ethyl Acetate Fraction from Smilax china L. and Determination of Xanthine Oxidase Inhibitory Properties

The aim of this work was to investigate the xanthine oxidase (XO)-inhibitory activity of ethanol extracts from Smilax china L. and to identify the active compounds in the ethyl acetate (EtOAc) fraction. Extraction of ethanol extracts from Smilax china L. and then ethanol extracts were concentrated, and the polyphenolic compounds were extracted with petroleum ether (PE), chloroform, EtOAc, n-butanol (n-BuOH), and residual ethanol fractions. Their effects on XO activity were then compared separately. The polyphenolic components of the EtOAc fraction were identified by HPLC and HPLC-mass spectrometry (HPLC-MS) analysis. Kinetic analysis demonstrated that all these extracts showed XO-inhibitory properties, and among them the EtOAc fraction had the strongest inhibitory effect (IC₅₀ = 101.04 μg/mL). The inhibitory constant (K_i) of the EtOAc fraction on XO activity was 65.20 μg/mL, showing excellent inhibition on XO in the competitive mode. Sixteen compounds were identified from the EtOAc fraction. The study demonstrates that the EtOAc fraction of Smilax china L. may be a potential functional food to inhibit XO activity.

Linum corymbulosum Protects Rats against CCl4-Induced Hepatic Injuries through Modulation of an Unfolded Protein Response Pathway and Pro-Inflammatory Intermediates

Liver fibrosis is a major pathological feature of chronic liver disease and effective therapies are limited at present. The present study focuses on the hepatoprotective potential of L. corymbulosum against carbon tetrachloride (CCl4)-induced liver damage in rats. Analysis of Linum corymbulosum methanol extract (LCM) using high-performance liquid chromatography (HPLC) revealed the presence of rutin, apigenin, catechin, caffeic acid and myricetin. CCl4 administration lowered (p < 0.01) the activities of antioxidant enzymes and reduced glutathione (GSH) content as well as soluble proteins, whereas the concentration of H2O2, nitrite and thiobarbituric acid reactive substances was higher in hepatic samples. In serum, the level of hepatic markers and total bilirubin was elevated followed by CCl4 administration. The expression of glucose-regulated protein (GRP78), x-box binding protein-1 total (XBP-1 t), x-box binding protein-1 spliced (XBP-1 s), x-box binding protein-1 unspliced (XBP-1 u) and glutamate-cysteine ligase catalytic subunit (GCLC) was enhanced in CCl4-administered rats. Similarly, the expression of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and monocyte chemo attractant protein-1 (MCP-1) was strongly increased with CCl4 administration to rats. Co-administration of LCM along with CCl4 to rats lowered (p < 0.05) the expression of the above genes. Histopathology of the liver showed hepatocyte injury, leukocyte infiltration and damaged central lobules in CCl4-treated rats. However, LCM administration to CCl4-intoxicated rats restored the altered parameters towards the levels of control rats. These outcomes indicate the existence of antioxidant and anti-inflammatory constituents in the methanol extract of L. corymbulosum.

Dietary Flavonoid Intake and Cancer Mortality: A Population-Based Cohort Study

Cancer is a leading cause of death worldwide, posing a huge burden upon society and individuals. The adequate intake of fruit and vegetables is reported to be an effective strategy for primary cancer prevention. Fruits and vegetables are rich in nutrients, such as vitamins and flavonoids, which may reduce the occurrence and progression of cancers. However, the importance of each flavonoid and the sub-classes remains controversial regarding cancer mortality. The population benefiting from increased flavonoid intake has not been determined. An estimation of cancer mortality by flavonoid intake is not established. We explored the association between the intake of flavonoids and cancer mortality amongst 14,029 participants in the National Health and Nutrition Examination Survey. During a median follow-up of 117 months, 405 cancer deaths were confirmed. Being in the second, third, and fourth quartiles of flavonol intake, the cancer mortality was inversely associated with the intake of flavonols (multivariate analysis HR (95% CI] 0.58 [0.36, 0.91], p = 0.02, Q1 vs. Q2; 0.55 [0.31, 0.96], p = 0.04, Q1 vs. Q3; 0.54 [0.30, 0.99], p = 0.05, Q1 vs. Q4, respectively). Potential effects of dietary flavonol intake against cancer death was observed especially in participants aged 50 or above, males, whites, former smokers, people who used to drink or drink alcohol mildly, people without hyperlipidemia, and people with hypertension. Moreover, the dietary intakes of peonidin, naringenin, and catechin were inversely associated with cancer mortality (multivariate HR [95% CI] 0.93 [0.88,0.98], p = 0.01; 0.97 (0.95,1.00), p = 0.03; 0.98 (0.96,1.00), p = 0.05, respectively). Furthermore, a nomogram based on flavonol intake is feasible for assessing cancer mortality for each participant. Taken together, our results could improve personalized nutrition amongst cancer patients.

Prophylactic and curative effects of Carica papaya Linn. pulp extract against carbon tetrachloride-induced hepatotoxicity in male rats

Several chemicals and medications induce cellular damage in various organs of the body by activating reactive substances' metabolism leading to various pathological conditions including liver disease. In this study, we evaluated the prophylactic and curative effects of Carica papaya Linn. pulp water extract (PE) against CCl4-induced rat hepatotoxicity. Five groups of rats were created, control, PE, CCl4, (PE-CCl4): The rats were administered with PE pre and during CCl4 injection, and (PE-CCl4-PE): The rats were administered with PE pre, during, and after CCl4. The markers of oxidative stress ("OS": oxidant and antioxidants), inflammation [nuclear factor-κB, tumor necrosis factor-α, and interleukin-6], fibrosis [transforming growth factor-β], and apoptosis [tumor suppressor gene (p53)] were evaluated. Additionally, liver functions, liver histology, and kidney functions were measured. Also, PE characterization was studied. The results showed that PE, in vitro, has a high antioxidant capacity because of the existence of phenolics, flavonoids, tannins, terpenoids, and minerals. Otherwise, the PE administration [groups (PE-CCl4) and (PE-CCl4-PE)] exhibited its prophylactic and therapeutic role versus the hepatotoxicity induced by CCl4 where PE treatment improved liver functions, liver histopathology, and renal functions by decreasing oxidative stress, inflammation, fibrosis, and apoptosis induced by CCl4. Our study elucidated that PE contains high amounts of phenolics, flavonoids, tannins, terpenoids, and ascorbic acid. So, PE exerted significant prophylactic and curative effects against hepatotoxicity induced by CCl4. These were done by enhancing the markers of antioxidants and drug-metabolizing enzymes with reductions in lipid peroxidation, inflammation, fibrosis, and apoptosis. PE administration for healthful rats for 12 weeks had no negative impacts. Consequently, PE is a promising agent for the prohibition and therapy of the toxicity caused by xenobiotics.

Bioaffinity ultrafiltration coupled with HPLC-ESI-MS/MS for screening potential α-glucosidase inhibitors from pomegranate peel

Pomegranate peel (PoP) contains plenty of bioactive compounds and exhibits strong activity to prevent postprandial hyperglycaemia and improve diabetes mellitus. Presently, bioaffinity ultrafiltration coupled with high performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ESI-MS/MS) is employed to screen and identify the efficient α-glucosidase inhibitors in PoP and the detailed inhibitory mechanisms are further investigated. The results show that many substances, including ellagic acid, kaempferol, gallic acid, and resveratrol in PoP reveal strong activity to inhibit α-glucosidase and ellagic acid (EA) is screened as the most effective compound. Further research indicates that EA plays a competitive and reversible inhibition role against α-glucosidase with the value of Ki was 6.24 × 105 mol/L. EA also directly interacts with the amino acids of α-glucosidase mainly via van der Waals forces and hydrogen bonds, thereby, influencing the secondary structure and stability of α-glucosidase. Finally, the α-glucosidase inhibitory activity of EA is further confirmed to significantly reduce postprandial blood glucose in vivo.

Tetrabutylammonium bromide-based hydrophobic deep eutectic solvent for the extraction and separation of dihydromyricetin from vine tea and its inhibitory efficiency against xanthine oxidase

In this study, deep eutectic solvent oscillation-assisted extraction (DES-OS) combined with macroporous resin adsorption and desorption technology was used to achieve the rapid green extraction and separation of the characteristic component dihydromyricetin (DMY) from vine tea. Multivariate data analysis showed that the DES system composed of tetrabutylammonium bromide (N₄₄₄Br) and pyruvic acid (molar ratio 1 : 2) had good extraction performance for DMY. The influence parameters of DES-OS were studied, and optimized by the single-factor test and response surface methodology (RSM) with Box–Behnken design (BBD). The extraction model of DMY was established and verified. The results showed that the extraction yield of DMY could reach 40.1 mg g⁻¹ under the optimal conditions (DES water contents of 71.18%, extraction time of 2.80 h, extraction temperature of 46.40 °C), which is in good agreement with the predicted value. In addition, Fourier transform infrared spectroscopy (FT-IR) was used to characterize the solvent before and after extraction. Scanning electron microscopy (SEM) results further confirmed that tetrabutylammonium bromide:pyruvate enhanced the destruction of the cell wall structure, resulting in the release of more DMY. Furthermore, different macroporous resins were selected for the separation of DMY for the DES-OS extract, and it was found that the DM301 resin had the ideal recovery performance under optimized dynamic condition. Finally, the product was found to have an inhibitory effect against xanthine oxidase (XO) as a mixed-type competitive inhibitor with IC50 values of (5.79 ± 0.22) × 10⁻⁵ mol L⁻¹. The inhibitory mechanisms of DMY on XO were explored by enzyme kinetics, spectroscopy, molecular docking and molecular dynamics analysis approaches, which provided a theoretical basis for the above inhibition assays.

In this study, deep eutectic solvent oscillation-assisted extraction (DES-OS) combined with macroporous resin adsorption and desorption technology was used to achieve the rapid green extraction and separation of dihydromyricetin (DMY) from vine tea.

LC-MS/MS Phytochemical Profiling, Antioxidant Activity, and Cytotoxicity of the Ethanolic Extract of Atriplex halimus L. against Breast Cancer Cell Lines: Computational Studies and Experimental Validation

Atriplex halimus L., also known as Mediterranean saltbush, and locally as "Lgtef", an halophytic shrub, is used extensively to treat a wide variety of ailments in Morocco. The present study was undertaken to determine the antioxidant activity and cytotoxicity of the ethanolic extract of A. halimus leaves (AHEE). We first determined the phytochemical composition of AHEE using a liquid chromatography (LC)-tandem mass spectrometry (MS/MS) technique. The antioxidant activity was evaluated using different methods including DPPH scavenging capacity, β-carotene bleaching assay, ABTS scavenging, iron chelation, and the total antioxidant capacity assays. Cytotoxicity was investigated against human cancer breast cells lines MCF-7 and MDA-MB-231. The results showed that the components of the extract are composed of phenolic acids and flavonoids. The DPPH test showed strong scavenging capacity for the leaf extract (IC₅₀ of 0.36 ± 0.05 mg/mL) in comparison to ascorbic acid (IC₅₀ of 0.19 ± 0.02 mg/mL). The β-carotene test determined an IC₅₀ of 2.91 ± 0.14 mg/mL. The IC₅₀ values of ABTS, iron chelation, and TAC tests were 44.10 ± 2.92 TE µmol/mL, 27.40 ± 1.46 mg/mL, and 124 ± 1.27 µg AAE/mg, respectively. In vitro, the AHE extract showed significant inhibitory activity in all tested tumor cell lines, and the inhibition activity was found in a dose-dependent manner. Furthermore, computational techniques such as molecular docking and ADMET analysis were used in this work. Moreover, the physicochemical parameters related to the compounds' pharmacokinetic indicators were evaluated, including absorption, distribution, metabolism, excretion, and toxicity prediction (Pro-Tox II).

Anserine beneficial effects in hyperuricemic rats by inhibiting XOD, regulating uric acid transporter and repairing hepatorenal injury

This study aims to investigate the anti-hyperuricemia effect and mechanism of anserine in hyperuricemic rats. Hyperuricemic rats were induced with a combination of 750 mg per kg bw d potassium oxazinate (PO) and 200 mg per kg bw d hypoxanthine for a week, and the rats were separately orally administered anserine (20, 40, 80 mg kg^-1) and allopurinol (10 mg kg^-1) for three weeks. The results show that the content of serum uric acid (SUA) decreased by approximately 40% and 60% after the intervention of anserine and allopurinol, respectively. The activity of superoxide dismutase (SOD) was increased and the levels of malondialdehyde (MDA), alkaline phosphatase (ALP) and alanine aminotransferase (ALT) were significantly decreased in the anserine groups. After the administration of anserine, the contents of blood urea nitrogen (BUN) and creatinine (Cr) were reduced in the kidney, and the levels of the proinflammatory cytokines IL-1β, IL-6β, TNF-α and TGF-β and inflammatory cell infiltration were reduced in both the liver and kidney. Moreover, the gene expressions of xanthine oxidase (XOD), renal urate transporter 1 (URAT1) and glucose transporter type 9 (GLUT9) were downregulated by anserine administration, and the gene expressions of ATP-binding cassette transporter G2 (ABCG2), organic anion transporter 1 (OAT1) and organic anion transporter 3 (OAT3) were upregulated at the same time. These findings suggest that hepatorenal injury was repaired by anserine, which further regulated the expression of hepatic XOD and renal URAT1, GLUT9, ABCG2, OAT1 and OAT3 to relieve hyperuricemia in rats.

The inhibitory kinetics and mechanism of quercetin-3-O-rhamnoside and chlorogenic acid derived from Smilax china L. EtOAc fraction on xanthine oxidase

Smilax china L. showed various biological activities mainly due to its phenolic components; however, the mechanism of isolated phenolic fraction against xanthine oxidase (XO) has not been investigated. Quercetin-3-O-rhamnoside (QORh) and chlorogenic acid (CGA) extracted from Smilax china L. ethyl acetate fraction was analyzed for its XO inhibitory kinetics and mechanism using multispectroscopic methods and molecular docking techniques. QORh and CGA reversibly inhibited XO activity in competitive and non-competitive modes, respectively. The bioactive compounds bound with XO were dominated mainly by hydrogen bonds and van der Waals forces to form QORh-XO, and CGA-XO complexes with one affinity binding site. The synchronous fluorescence, circular dichroism, three-dimensional (3D) fluorescence, and Fourier transform infrared spectra exhibited that XO binding with QORh or CGA leads to the secondary and tertiary structural variation of the protein. Additionally, molecular docking further revealed that QORh binds to the active site of XO and forms hydrogen coupling with amino acid residues. The results showed that QORh and CGA had inhibitory activity on XO, which might be further used to modify the bioactive compounds and improve their efficacy to treat gout.

Exploring the binding mechanism of ferulic acid and ovalbumin: insights from spectroscopy, molecular docking and dynamics simulation

BACKGROUND

Ferulic acid (FA), a phenolic acid widely occurring in nature, has attracted extensive attention because of its biological activity. Ovalbumin (OVA) is a commonly used carrier protein. The mechanism of FA binding with OVA was investigated by utilizing a variety of spectral analyses, accompanied by computer simulation.

RESULTS

It was discovered that the fluorescence quenching mechanism of OVA by FA was a static mode as a result of the formation of an FA-OVA complex, which was verified by the concentration distributions and pure spectrum of the constituents decomposed from the high overlap spectrum signals using multivariate curve resolution-alternate least squares algorithm. Hydrogen bonds and Van der Waals forces drove the formation of FA-OVA complex with a binding constant of 1.69 × 10⁴  L mol^-1 . The presence of FA induced the loose structure of OVA with an attenuation of α-helix content and improved the thermal stability of OVA. Computer docking indicated that FA interacted with the amino acid residues Arg84, Asn88, Leu101 and Ser103 of OVA through hydrogen bonds. Molecular dynamics simulation proved that the combination of FA with OVA boosted the conformational stability of OVA and hydrogen bonds brought a crucial part in stabilizing the structure of the complex.

CONCLUSIONS

The study may supply the theoretical basis for the design of FA transport system using OVA as carrier protein to improve the instability and low bioavailability of FA. © 2021 Society of Chemical Industry.

Characterization of xanthine oxidase inhibitory activities of phenols from pickled radish with molecular simulation

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The 2,6-Dihydroxyacetophenone (DHAP), 4-Hydroxyphenethyl alcohol (4-HPEA), and 4-Hydroxybenzaldehyde (HBA) in pickled radish showed a good affinity for xanthine oxidase (XOD) in the molecular docking results.

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DHAP, 4-HPEA and HBA inhibit in vitro XOD enzymatic activity by affecting secondary structure and hydrophobic groups, IC₅₀ were: 1.24 ± 0.02 mM, 24.52 ± 0.8 mM, and 2.67 ± 0.9 µM, respectively.

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DHAP, 4-HPEA and HBA reduce xanthine-induced high uric acid levels in BRL 3A cells by inhibiting XOD enzyme activity (p < 0.05).

Pickled radish is a general source of natural bioactive compounds that include phenols. Here, we used molecular docking, fluorescence quenching, circular dichroism spectroscopy and molecular dynamics simulations to identify potential inhibitors against xanthine oxidase from a library of pickled radish compounds. The most effective compounds were selected for validation through in vitro experiments including enzyme activity inhibition tests, and cell-based assays. Molecular docking results revealed that 2,6-Dihydroxyacetophenone, 4-Hydroxyphenethyl alcohol, and 4-Hydroxybenzaldehyde exhibited significant effects on xanthine oxidase inhibition. Three phenols have varying degrees of inhibition on xanthine oxidase, which is driven by hydrophobic interactions and hydrogen bonds and affects the secondary structure and hydrophobic homeostasis of xanthine oxidase. The stability of xanthine oxidase inhibition by three phenols was analyzed by molecular dynamics simulation. Finally, cellular experiments confirmed that three phenols reduced uric acid levels by inhibiting the xanthine oxidase enzyme activity of BRL 3A cells.

Multi-Spectroscopic and Molecular Simulation Approaches to Characterize the Intercalation Binding of 1-Naphthaleneacetic Acid With Calf Thymus DNA

1-Naphthaleneacetic acid (NAA), having high-quality biological activity and great yield-increasing potential in agricultural production, is a broad-spectrum plant growth regulator. Although NAA is of low toxicity, it can affect the balance of the human metabolism and damage the body if it is used in high quantity for a long time. In this study, the interaction of NAA with calf thymus DNA (ctDNA) was investigated under simulated human physiological acidity (pH 7.4) using fluorescence, ultraviolet-visible absorption, and circular dichroism spectroscopy combined with viscosity measurements and molecular simulation techniques. The quenching of the endogenous fluorescence of NAA by ctDNA, observed in the fluorescence spectrum experiment, was a mixed quenching process that mainly resulted from the formation of the NAA-ctDNA complex. NAA mainly interacted with ctDNA through hydrophobic interaction, and the binding constant and quenching constant at room temperature (298 K) were 0.60 × 10⁵ L mol^-1 and 1.58 × 10⁴ L mol^-1, respectively. Moreover, the intercalation mode between NAA and ctDNA was verified in the analysis of melting point, KI measurements, and the viscosity of ctDNA. The results were confirmed by molecular simulation, and it showed that NAA was enriched near the C-G base of ctDNA. As shown in circular dichroism spectra, the positive peak intensity of ctDNA intensified along with a certain degree of redshift, while the negative peak intensity decreased after binding with NAA, suggesting that the binding of NAA induced the transformation of the secondary structure of ctDNA from B-form to A-form. These researches will help to understand the hazards of NAA to the human body more comprehensively and concretely, to better guide the use of NAA in industry and agriculture.

Enhancement of oral bioavailability and anti-hyperuricemic activity of aloe emodin via novel Soluplus®-glycyrrhizic acid mixed micelle system

The objective of this study was to fabricate a novel drug delivery system using Soluplus® (polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer) and glycyrrhizic acid to improve solubility, bioavailability, and anti-hyperuricemic activity of aloe emodin (AE). The AE-loaded mixed micelles (AE-M) were prepared by thin-film hydration method. The optimal AE-M contained small-sized (30.13 ± 1.34 nm) particles with high encapsulation efficiency (m/m, %) of 90.3 ± 1.08%. The release rate of AE increased in the micellar formulation than that of free AE in the four media (DDW, pH 7.0; phosphate buffer solution, pH 7.4; phosphate buffer solution, pH 6.8; and hydrochloric acid aqueous solution, pH 1.2). In comparison to free AE, the pharmacokinetic study of AE-M showed that its relative oral bioavailability increased by 3.09 times, indicating that mixed micelles may promote gastrointestinal absorption. More importantly, AE-M effectively reduced uric acid level by inhibiting xanthine oxidase (XOD) activity in model rats. The degree of ankle swelling, serum levels of interleukin (IL)-1, and IL-6-related inflammatory factors levels all decreased in the gouty arthritis model established via monosodium urate (MSU) crystals. Taken together, the AE-M demonstrated the potential to improve the bioavailability, anti-hyperuricemic activity, and anti-inflammation of AE.

Stilbene compounds are specific inhibitors of the superoxide anion generation catalyzed by xanthine oxidase

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Stilbenes suppress O₂-generation catalyzed by XO more than uric acid formation.

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O₂- suppression induced by stilbenes is due to the binding to FAD site in XO.

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Stilbenes attenuate the oxidative stress induced by increase of XO.

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Piceatannol suppresses the O₂- generation more than other stilbenes.

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The suppression is induced by binding to FAD site and reduction of XO.

The inhibitory effect of xanthine oxidase (XO) reactions with stilbene compounds, 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging by stilbene compounds and superoxide anion (O₂-) scavenging activity were examined. The inhibition of the O₂- generation catalyzed by XO by stilbene compounds is stronger than the effect on uric acid formation. The suppression of the O₂- generation with resveratrol was diminished by the addition of flavin adenine dinucleotide (FAD). The water-solubility and visible spectra (VIS) of the stilbene compounds in the presence of water-soluble flavin compounds indicated a π-π interaction between the stilbene compounds and the isoalloxazine in flavin compounds. These results indicate that stilbene compounds specifically bind the FAD site in XO so as to inhibit the O₂- generation. In the case of piceatannol, it is deduced that the suppression of O₂- generation is induced by this specific binding to the FAD site and the subsequent reduction of XO.

Separation, Purification, Structure Analysis, In Vitro Antioxidant Activity and circRNA-miRNA-mRNA Regulatory Network on PRV-Infected RAW264.7 Cells of a Polysaccharide Derived from Arthrospira platensis

To investigate the structure of Arthrospira platensis polysaccharide (PAP) (intracellular polysaccharide) and the antioxidant activity of the first component of PAP (PAP-1) on pseudorabies virus (PRV) -infected RAW264.7 cells. The PAP was separated and purified by the Cellulose DE-52 chromatography column and Sephacryl S-200 high-resolution gel column to obtain PAP-1. The antioxidant activity and regulation of PAP-1 on PRV-infected RAW264.7 cells of circRNA-miRNA-mRNA network were investigated by chemical kit, Q-PCR, and ce-RNA seq. The results indicated that the molecular weight (Mw) of PAP-1, which was mainly composed of glucose and eight other monosaccharides, was 1.48 × 106 Da. The main glycosidic bond structure of PAP-1 was →4)-α-D-Glcp-(1→. PAP-1 may be increased the antioxidant capacity by regulating the circRNA-miRNA-mRNA network in PRV-infected RAW264.7 cells. This study provided a scientific foundation for further exploring the antioxidant activity of PAP-1 based on its structure.

Epicatechin Gallate as Xanthine Oxidase Inhibitor: Inhibitory Kinetics, Binding Characteristics, Synergistic Inhibition, and Action Mechanism

Epicatechin gallate (ECG) is one of the main components of catechins and has multiple bioactivities. In this work, the inhibitory ability and molecular mechanism of ECG on XO were investigated systematically. ECG was determined as a mixed xanthine oxidase (XO) inhibitor with an IC50 value of 19.33 ± 0.45 μM. The promotion of reduced XO and the inhibition of the formation of uric acid by ECG led to a decrease in O2- radical. The stable ECG-XO complex was formed by hydrogen bonds and van der Waals forces, with the binding constant of the magnitude of 104 L mol-1, and ECG influenced the stability of the polypeptide skeleton and resulted in a more compact conformation of XO. Computational simulations further characterized the binding characteristics and revealed that the inhibitory mechanism of ECG on XO was likely that ECG bound to the vicinity of flavin adenine dinucleotide (FAD) and altered the conformation of XO, hindering the entry of substrate and the diffusion of catalytic products. ECG and allopurinol bound to different active sites of XO and exerted a synergistic inhibitory effect through enhancing their binding stability with XO and changing the target amino acid residues of XO. These findings may provide a theoretical basis for the further application of ECG in the fields of food nutrition and functional foods.

Design, synthesis and bioactive evaluation of geniposide derivatives for antihyperuricemic and nephroprotective effects

Hyperuricemia is a principal factor mediating gout and kidney damage, and xanthine oxidase (XOD) is a key enzyme in the pathogenesis of hyperuricemia. In this context, a series of geniposide derivatives were designed and synthesized, and antihyperuricemic and nephroprotective effects of all derivatives was evaluated in vitro and in vivo. Compound 2e emerged as the most potent XOD inhibitor, with an IC₅₀ value of 6.67 ± 0.46 µM. Simultaneously, cell viability, ROS generation, and SOD levels assay showed that compound 2e could repair the damage of HKC cells by inhibiting the oxidative stress response. The results of the study indicated compound 2e significantly decreased uric acid levels by inhibiting the XOD activity, and repaired kidney damage by inhibiting the expression of TLR4/TLR2/MyD88/NF-κB and NALP3/ASC/caspase-1 signaling pathways. Enzyme inhibition kinetics suggested that compound 2e functioned via reversible mixed competitive inhibition. Moreover, a molecular docking study was performed to gain insight into the binding mode of compound 2e with XOD. These results suggest that geniposide derivatives were potential to be developed into a novel medicine to reveal healthy benefits in natural prevention and reduction risk of hyperuricemia and kidney damage.

Binding mechanism of 4-octylphenol with human serum albumin: Spectroscopic investigations, molecular docking and dynamics simulation

4-Octylphenol (OP) is an environmental estrogen that can enter organisms through the food chain and cause various toxic effects. Here, the interaction between OP and human serum albumin (HSA) was explored through multipectral, molecular docking and dynamics simulation. The results showed that OP and HSA formed a ground state complex through a static quenching mechanism, and the interaction was spontaneously driven by hydrogen bonds and hydrophobic interaction forces. The binding constant at different temperatures was measured to be on the order of 10⁵ L mol^-1. Site competition experiments suggested that OP interacted with amino acid residues Lys195, Cy245 and Cys246 located at the Sudlow site I of HSA, resulting in a more stretched protein peptide. The presence of OP increased the surface hydrophobicity of HSA, and reduced the content of α-helix in HSA by 3.4%. FT-IR spectra showed that OP interacted with the C=O and C-H groups of the polypeptide backbone. Molecular docking demonstrated that OP mainly bound to Site I of HSA and hydrogen bonds participated in the interaction. In addition, molecular dynamics simulations further explored the stability and dynamic behavior of the OP-HSA complex through RMSD, RMSF, SASA and Rg.

Spectroscopic and docking studies of the interaction mechanisms of xylitol with α-casein and κ-casein

The molecular interactions of xylitol (XY) with α-casein (α-CN) and κ-casein (κ-CN) at pH 7.4 as a function of temperature (298, 308, and 318 K) were characterized by multispectral techniques and molecular docking. The fluorescence results showed that XY strongly quenched the intrinsic fluorescence of α- and κ-CN by static quenching, as well as the presence of a single binding site for XY on both proteins with a binding constant value of ∼10⁵ L/mol. The binding affinity of both proteins for XY decreased with increasing temperature, and Van der Waals forces, hydrogen bonding and protonation were the key forces in the interactions. The addition of XY altered the polarity of the microenvironment of proteins and changed their secondary structure from ordered to disordered. The molecular docking results showed that XY had different binding sites to α- and κ-CN, with several amino acids involved in the binding processes.

Inhibitory mechanism of xanthine oxidase activity by caffeoylquinic acids in vitro

In this study, the inhibitory activities of eight caffeoylquinic acids (CQAs) against xanthine oxidase (XOD) in vitro were investigated, and the interaction mechanisms between each compound and XOD were studied. HPLC and fluorescence spectra showed that the inhibitory activities of dicaffeoylquinic acids (diCQAs) were higher than that of monocaffeoylquinic acids (monoCQAs), due to the main roles of hydrophobic interaction and hydrogen bond between XOD and diCQAs. Both the binding constant and the lowest binding energy data indicated that the affinities of diCQAs to XOD were stronger than that of monoCQAs. Circular dichroism showed that the structure of XOD was compacted with the increased of α-helix content, resulting in decreased enzyme catalytic activity. Molecular docking revealed that CQAs preferentially bind to the flavin adenine dinucleotide region in XOD. These results provided the mechanisms of CQAs on inhibiting XOD and the further utilization of CQAs as XOD inhibitors to prevent hyperuricemia.

Effect of quercetin on the in vitro Tartary buckwheat starch digestibility

Tartary buckwheat is one of the few pseudocereals with abundant flavonoids and starch. However, there are different views on the digestibility of Tartary buckwheat starch (TBS) because of its particle size and structure. In this study, fluorescence spectrum methods and enzymatic kinetics were used to investigate the interaction between TBS /two glycosidase (α-amylase and α-glucosidase) and quercetin to explore its digestive properties and provide a perspective regarding the application of TBS in functional starch products. The results showed that the interaction between TBS and quercetin was probably weak hydrophobic force and hydrogen bonding. The inhibitory effect of quercetin on α-amylase was better than that on α-glucosidase. The half inhibitory concentrations (IC₅₀) of quercetin to α-amylase and α- glucosidase was (270 ± 3.31) and (544 ± 9.01) μg/mL, respectively. The intrinsic fluorescence of two enzymes was statically quenched by forming a complex with quercetin. Quercetin also increased the microenvironment hydrophilicity of tryptophan residues in glycosidase. In vitro digestion experiment demonstrated that quercetin and TBS co-gelatinized together was more effective to inhibit TBS hydrolysis than quercetin itself alone. In the first-order kinetic and LOS model, quercetin-starch gel structure and quercetin inhibitory activity against enzymes had synergistic effects of the TBS digestion.

Structural and kinetic insights into HIV-1 reverse transcriptase inhibition by farnesiferol C

Human immunodeficiency virus type 1 reverse transcriptase (HIV-1 RT) is the key enzyme for the virus gene replication and the most important target for antiviral therapy. Toxicity, drug resistance and side effects have led to search for new antiviral agents. Farnesiferol C (FC) is a well-known biologically active sesquiterpene coumarin derivative from genus Ferula. The current study was designed to examine the impacts of FC on the structure and function of HIV-1 RT, using some theoretical and experimental methods. FC inhibited HIV-1RT activity via mixed inhibition mechanism (IC₅₀ = 30 μM). Spectroscopic data showed some conformational changes in the secondary as well as tertiary structure of HIV-1RT following the interaction with FC. Results showed that FC could quench the intrinsic fluorescence emission of HIV-1RT through static quenching mechanism. Thermodynamic parameters revealed that hydrogen bondings and van der Waals forces are the major forces in the binding reaction and the low equilibrium constants (K_D) value obtained from surface plasmon resonance data, confirmed the high affinity of FC for HIV-1RT. Molecular docking studies indicated that FC interacts with enzyme through hydrophobic pocket. Taken together, the outcomes of this research revealed that, sesquiterpene coumarines can be used to design natural remedies as anti-HIV agents.

Three flavanols delay starch digestion by inhibiting α-amylase and binding with starch

The study aimed to reveal the different mechanisms of delaying starch digestion by ECG, EGCG and Procyanidin based on the perspective of α-amylase-flavanol interaction and starch-flavanol interaction. The interaction characteristics of flavanols with α-amylase were studied from five aspects: enzyme inhibition, kinetics, fluorescence quenching, circular dichroism (CD) and computer simulation. The IC50 of flavanols (ECG, EGCG and Procyanidin) against α-amylase were 172.21 ± 0.22, 732.15 ± 0.13 and 504.45 ± 0.19 μg/mL according to the results of α-amylase inhibition experiment, respectively. ECG and Procyanidin showed mixed inhibition against α-amylase, while EGCG showed non-competition against α-amylase. However, thermodynamic parameters，computer-based docking and dynamic simulation proved that ECG and EGCG-α-amylase complexs were mainly driven by van der Waals and hydrogen bonds, while Procyanidin-α-amylase complexs was driven by hydrophobic interaction. In addition, it was indicated, by means of starch‑iodine complex spectroscopy, that flavanols inhibited the digestion of starch not only through bind with α-amylase but also through bind with starch. Thus, flavanols as a starch-based food additive have the potential to be employed as adjuvant therapy for diabetes.

Inhibition mechanism: Phytic acid, NADH as a peroxidase inhibitor

Peroxidase, a key enzyme causing enzymatic browning, and affected the potential values of fruit and vegetables. Phytic acid and NADH inhibited peroxidase in a competitive manner due to their reducing properties, and it's IC₅₀ (1.18 ± 0.32) × 10^-8, (8.02 ± 0.45) × 10^-6 mol L^-1, respectively. The interaction between phytic acid, NADH and peroxidase contributed to intrinsic fluorescence quenching and conformation alternation with a accuracy determination by multispectroscopic techniques (fluorescence spectra, FT-IR and CD spectra), respectively. Molecular docking simulation revealed that phytic acid, NADH interacted with His170, Ala34, Arg38, Ser73, Arg31, Lys174, Gln176, Asn175, Arg75; Gln176, Asn175, Phe221, Lys174, Gly173, Ser167, Phe172, Gly169, His170 in peroxidase, respectively and blocked substrates into catalytic reactions.

The inhibition mechanism of luteolin on peroxidase based on multispectroscopic techniques

Luteolin, a plant-derived flavonoid, was found to exert effective inhibitory effect to peroxidase activity in a non-competitive manner with an IC50 of (6.62 ± 0.45) × 10-5 mol L-1. The interaction between luteolin and peroxidase induced the formation of a static complex with a binding constant (Ksv) of 7.31 × 103 L mol-1 s-1 driven by hydrogen bond and hydrophobic interaction. Further, the molecular interaction between luteolin and peroxidase resulted in intrinsic fluorescence quenching, structural and conformational alternations which were determined by multispectroscopic techniques combined with computational molecular docking. Molecular docking results revealed that luteolin bound to peroxidase and interacted with relevant amino acid residues in the hydrophobic pocket. These results will provide information for screening additional peroxidase inhibitors and provide evidence of luteolin's potential application in preservation and processing of fruit and vegetables and clinical disease remedy.

Green and Facile Synthesis and Antioxidant and Antibacterial Evaluation of Dietary Myricetin-Mediated Silver Nanoparticles

Myricetin (MY) is a dietary flavonoid which exhibits a wide spectrum of biological properties, viz., antibacterial, antioxidant, anticancer, and so forth. The lower solubility in aqueous medium and hence lesser bioavailability of MY limits the use of such dietary flavonoids in further in vivo research. To overcome bioavailability limitations, a number of drug-delivery systems are being investigated. Herein, MY-mediated silver nanoparticles (MY-AgNPs) were synthesized by a green approach to improve the therapeutic efficacy of MY. MY-AgNPs were characterized by ultraviolet-visible spectroscopy (UV-Vis), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, and X-ray powder diffraction (XRD). The results showed that the dispersion of AgNPs had the maximum UV-vis absorption at about 410 nm. The synthesized nanoparticles were almost spherical. MY-AgNPs were further investigated against human pathogenic bacteria, and their antioxidant potential was also determined. The free radical scavenging rate was about 60-87%. MY-AgNPs had good antibacterial activity against Escherichia coli and Salmonella at room temperature with minimum inhibitory concentrations of 10-4 and 10-5 g/L, respectively.

Application of multi-dimensional and multi-informational (MD-MI) integrated xanthine oxidase and superoxide anion fingerprint in quality evaluation of Scutellariae Radix

A multi-hyphenated analytical method that was successfully established in previous research was applied to quality evaluation of traditional Chinese medicine (TCM) to verify its feasibility in complex systems. Scutellariae Radix (SR), which significantly protects against oxidative damage from ischemia and reperfusion, was selected as the TCM for this study. A dual-activity detection system based on xanthine oxidase (XOD) inhibition and superoxide anion (O₂^-) scavenging activity was used to generate a multi-dimensional-multi-informational (MD-MI) integrated fingerprint of SR. Combined with HPLC-ESI-Q-TOF-MS analysis, 17 active compounds in SR were tentatively identified by comparison with reference substances or literature data. The quality of SR from different habitats was comprehensively and systematically evaluated in respect of chemical composition, XOD inhibition and O₂^- scavenging activity. It was confirmed that SR contains many antioxidants and XOD inhibitory substances with diverse functions. Among them, baicalin, norwogonin-7-O-glucuronide and baicalein are the main contributors to direct antioxidant activity. Acteoside, 5,7,2',5'-tetrahydroxy-8,6'-dimethoxy flavone, baicalin and baicalein are the main XOD inhibitory components of SR. Comprehensive analysis found that the antioxidant activity of SR from Gansu Province was superior to that from other provinces in terms of both XOD inhibition and O₂^- scavenging activity. It has been demonstrated that the method is capable of analyzing complex TCM matrices, and can provide a useful reference for establishing quality control of TCM from the perspective of MD-MI.

A review on myricetin as a potential therapeutic candidate for cancer prevention

Myricetin, one of the most extensively studied polyphenols, is present abundantly in various fruits and vegetables and exhibits diverse pharmacological properties. The multifaceted biological action of myricetin against tumor heterogeneity makes it an impressive anticancer agent whose efficacy has been confirmed by an overwhelming number of studies. Myricetin shows its therapeutic potential by targeting and modulating the expression of various molecular target which are involved in inflammation, cell proliferation, apoptosis, angiogenesis, invasion, and metastasis. Myricetin deters tumor progression by inducing apoptosis via both intrinsic and extrinsic pathway, activating/inactivating several signaling pathways, and reactivating various tumor suppressor genes. This comprehensive review represents the effect of myricetin on various hallmarks of cancer with insight into the molecular mechanism employed by myricetin to mitigate cell proliferation, angiogenesis, metastasis, and induce apoptosis. In addition, enhanced bioavailability of myricetin through conjugation and its increased efficacy as an anticancer agent when used in combination are also highlighted.

In vitro and in silico Xanthine Oxidase Inhibitory Activity of Selected Phytochemicals Widely Present in Various Edible Plants

AIM AND OBJECTIVE

The present study was designed to evaluate the xanthine oxidase (XO) inhibitory and antioxidant activities of 30 bioactive compounds present in edible food plants for the possible treatment of hyperuricemia.

MATERIALS AND METHODS

The XO inhibitory, SO and DPPH radical scavenging activities of selected dietary polyphenols were determined by using colorimetric assays. The molecular docking analysis was performed to evaluate the insight into inhibitory mode of action of bioactive compounds against XO.

RESULTS

The results show that apigenin, galangin, kaempferol, quercetin, genistein and resveratrol potently inhibit XO enzyme among all tested compounds. Flavonoids exhibit higher, anthocyanins and hydroxycinnamic acids moderate, maslinic acid, ellagic acid, salicylic acid, [6]-gingerol and flavan-3-ols showed weak XO inhibitory activity. The results of molecular docking study revealed that these bioactive compounds bind with the active site of XO and occupy the active site which further prevents the entrance of substrate and results in the inhibition of XO.

CONCLUSION

Inhibition of XO gives a robust biochemical basis for management of hyperuricemia, gout and other associated diseases via controlling uric acid synthesis.

Molecular mechanisms of selenium-biofortified soybean protein and polyphenol conjugates in protecting mouse skin damaged by UV-B

Selenium-biofortified crops are a quality functional food resource because of their anti-tumor and anti-cancer properties. In the present study, the conjugates of selenium-biofortified soybean protein and polyphenols were prepared and evaluated by alkali-induced synthesis and in vitro antioxidant tests. Moreover, the antioxidant mechanisms of protecting mice skin damaged by UV-B were studied. The results showed that the antioxidant activity of the conjugate between 7S globulin from selenium-enriched soybean (Se-7S) and EGCG (Se-7S-EGCG) was significantly higher (P < 0.05) than that of Se-7S-GA. Structural characterizations implied that the polymerization of polyphenols with amino acid residues occurred. Se-7S-EGCG inhibited the apoptosis of epidermal cells induced by UV-B. The overexpression of phosphorylated proteins in the MAPK signaling pathway, the activation of related inflammatory factors, and the boost in the MMPs were reversed by Se-7S-EGCG. Overall, this research provides a theoretical and experimental basis for the application of protein and polyphenol conjugates in food and medicine fields.

Design, synthesis and antibacterial activities against Xanthomonas oryzae pv. oryzae, Xanthomonas axonopodis pv. Citri and Ralstonia solanacearum of novel myricetin derivatives containing sulfonamide moiety

BACKGROUND

Myricetin and sulfonamide derivatives exhibited a wide variety of biological activity. In order to develop highly bioactive molecules, novel myricetin derivatives containing sulfonamide moiety were synthesized and antibacterial activities were investigated.

RESULTS

The results of bioassays indicated that compound A12, having an EC₅₀ value of 4.7 μg mL^-1 , exhibited the best in vitro antibacterial activities against Xanthomonas oryzae pv. oryzae (X. oryzae pv. o.); EC₅₀ values for this compound were even better than those of thiodiazole-copper (TC, 71.4 μg mL^-1 ) and bismerthiazol (BT, 54.7 μg mL^-1 ). Compound A2, having an EC₅₀ value of 1.1 μg mL^-1 , exhibited the best in vitro antibacterial activities against Xanthomonas axonopodis pv. citri (X. axonopodis pv. c); values were notably better than those of TC (60.0 μg mL^-1 ) and BT (48.9 μg mL^-1 ). Scanning electron microscopy analysis indicated that compounds A2 and A12 caused the cell membranes of X. axonopodis pv. c and X. oryzae pv. o. to break or deform, respectively. When the concentration of compound A12 was 100 μg mL^-1 , the effective curative activity against bacterial leaf blight of rice was 44.2% in vivo and the effective protection activity was 58.2% in vivo, results that were both better than values for TC (18.9 and 21.4%, respectively) and BT (12.5 and 12.5%, respectively).

CONCLUSION

Novel myricetin derivatives containing a sulfonamide moiety were synthesized and bioassay results showed that compounds A2 and A12 exhibited the best antibacterial activities. © 2019 Society of Chemical Industry.