Xanthine Oxidase Inhibitory Activity Research Articles

Anti-hyperuricemia activity and its mechanism of flavonoid extract from saffron floral bio-residues

A hyperuricemic rat model induced by adenine and ethambutol was established to investigate the anti-hyperuricemia activity and its mechanism of the flavonoid extract from saffron floral bio-residues. Sixty-seven SD rats were randomly divided into control group, model group, positive control group, and flavonoid extract groups(with 3 doses), respectively, and each group contained 11 or 12 rats. The hyperuricemic model was established by continuous oral administration of adenine(100 mg·kg~(-1)) and ethambutol(250 mg·kg~(-1)) for 7 days. At the same time, the positive control group was given allopurinol(20 mg·kg~(-1) per day) and the flavonoid extract groups were given the flavonoid extract at doses of 340, 170 and 85 mg·kg~(-1) per day, respectively. On day 8, rat serum, liver, kidney, and intestinal tissues were collected, and the levels of uric acid in serum and tissue, the xanthine oxidase activities and antioxi-dant activities in serum and liver were evaluated, and the kidney histopathology was explored. In addition, an untargeted serum metabolomics study was performed. According to the results, the flavonoid extract effectively reduced the uric acid levels in serum, kidney and ileum and inhibited the xanthine oxidase activities and elevated the antioxidant activities of serum and liver in hyperuricemic rat. At the same time, it reduced the levels of inflammation factors in kidney and protected renal function. Moreover, 68 differential metabolites of hyperuricemic rats were screened and most of which were lipids and amino acids. The flavonoid extract significantly retrieved the levels of differential metabolites in hyperuricemic rats, such as SM(d18:1/20:0), PC[18:0/18:2(92,12Z)], palmitic acid and citrulline, possibly through the following three pathways, i.e., arginine biosynthesis, glycine, serine and threonine metabolism, and histidine metabolism. To sum up, the flavonoid extract of saffron floral bio-residues lowered the uric acid level, increased the antioxidant activity, and alleviated inflammatory symptoms of hyperuricemic rats, which may be related to its inhibition of xanthine oxidase activity and regulation of serum lipids and amino acids metabolism.

Phenolic Profile, Antioxidant, Antidiabetic, and Antigout Potential of Stem Extracts of Four Sweet Cherry Cultivars.

In order to highlight the activities of bioactive compounds present in the stem of sweet cherries, four different cultivars (Van, Burlat, Napoleon, and Cœur pigeon) were collected in Sefrou city in Morocco and were studied. Several assays were performed for this purpose, such as the quantification of phenolic compounds (TPC, TFC, and CTC) and the evaluation of the antioxidant activity using DPPH, ABTS, and FRAP assays. The phenolic profile of each extract was characterized by UHPLC-DAD/MS analysis. The antidiabetic (α-amylase inhibition) and antigout (xanthine oxidase inhibition) activities were also investigated. The results showed high levels of phenolic compounds, with the values of 340 ± 12.06, 244 ± 10.20, 232 ± 5.07, and 19 ± 3.10 mg gallic acid equivalent/g extract for the cultivars Napoleon, Coeur de pigeon, Van, and Burlat, respectively. According to the same order, the flavonoids showed amounts of 34.31 ± 2.08, 23.75 ± 1.02, 24.37 ± 1.20, and 23.31 ± 0.90 mg (rutin equivalent) RE/g extract. These values were correlated with the results of the antioxidant assays, where the Napoleon cultivar proved to be the most potent using the DPPH (IC50 = 2.51 µg/mL) and ABTS (IC50 = 55.38 µg/mL) assays. The phenolic profile of each extract resulted in the identification of twenty-two compounds belonging to five distinct groups. The major phenolic compounds identified were sakuranetin and dihydrowgonin with their glucosides. Antidiabetic activity assays showed that only stem extracts from Burlat and Napoleon cultivars were able to inhibit the α-amylase enzyme with values of 85.57 ± 1.09% and 68.01 ± 3.52%, respectively. All stem extracts proved their ability to inhibit the xanthine oxidase enzyme which is directly linked to the gout disease, with a high value for Van cultivar (40.63 ± 2.37%). These new findings could provide new opportunities for the valorization of cherry stems for the pharmaceutical application of their active phytochemicals.

Identification of coniferyl ferulate as the bioactive compound behind the xanthine oxidase inhibitory activity of Chuanxiong Rhizome

Identification of coniferyl ferulate as the bioactive compound behind the xanthine oxidase inhibitory activity of Chuanxiong Rhizome

Syntheses, Crystal Structures and Xanthine Oxidase Inhibitory Activity of Aroylhydrazones.

A series of hydrazones, (E)-N'-(4-hydroxy-3-methoxybenzylidene)-4-nitrobenzohydrazide (1), (E)-4-(dimethylamino)-N'-(4-hydroxy-3-methoxybenzylidene)benzohydrazide (2), N'-(2-hydroxy-5-methylbenzylidene)-4-nitrobenzohydrazide (3) and 2-fluoro-N'-(2-hydroxy-5-methylbenzylidene)benzohydrazide (4), were prepared and structurally characterized by elemental analysis, IR and 1H NMR spectra, and X-ray single crystal determination. The xanthine oxidase inhibitory activities of the compounds were investigated. Among the compounds, N'-(3-methoxybenzylidene)-4-nitrobenzohydrazide (1) showed the strongest activity. Docking simulations were performed to insert the compounds into the crystal structure of xanthine oxidase at the active site and to investigate the probable binding modes.

Chalcone derivatives as xanthine oxidase inhibitors: synthesis, binding mode investigation, biological evaluation, and ADMET prediction

Xanthine oxidase (XO) is a crucial target for the treatment of hyperuricemia and gout. A series of derivatives based on natural 3,4-dihydroxychalcone, obtained from Carthamus tinctorious and Licorice, were designed and synthesized. Nine derivatives (9a-e, 10b,c, and 15a,b) exhibited apparent XO inhibitory activity in vitro (IC50 values varied from 0.121 to 7.086 μM), 15b presented the most potent inhibitory activity (IC50 = 0.121 µM), which was 27.47-fold higher than that of allopurinol (IC50 = 3.324 µM). The SAR analysis indicated that introducing hydroxyl groups at 3′/4′/5′-position on ring A was more beneficial to the inhibition of XO than at 2′/6′-position; the removal of 3‑hydroxyl group on ring B could weaken the inhibitory potency of hydroxychalcones on XO, but it was beneficial to the XO inhibitory potency of methoxychalcones. Molecule modeling studies afforded insights into the binding mode of 15b with XO and supported the findings of SAR analysis. Additionally, kinetics studies demonstrated that 15b presented a reversible and competitive XO inhibitor, which spontaneously combined with XO through hydrophobic force, and finally changed the secondary conformation of XO. Furthermore, the acute hyperuricemia model was employed to investigate the hypouricemic effect of 15b, which could effectively reduce the serum uric acid levels of rats at an oral dose of 10 mg/kg. ADMET prediction suggested that compound 15b possessed good pharmacokinetic properties. Briefly, compound 15b emerges as an interesting XO inhibitor for the treatment of hyperuricemia and gout with beneficial effects on serum uric acid levels regulating. Meanwhile, the XO inhibitors with chalcone skeleton will deserve further attention and discussion.

Influence of Saccharomyces cerevisiae strains on fermentation of Monascus vinegar from rice pasta by-product

In the present work, rice pasta by-product (RPBP) was used as a raw material for the production of Monascus vinegar. Alcoholic fermentation using RPBP and red yeast rice koji were carried out, and the fermentative characteristics based on the yeast strains (Saccharomyces cerevisiae TISTR 5169, TISTR 5196, and TISTR 5197) were investigated. The compositional changes and functional properties of Monascus vinegar were examined. S. cerevisiae TISTR 5169 produced a higher yield of alcohol in a shorter time as compared to other strains, in which 10% alcohol was observed after four days of fermentation. Descriptive sensory evaluation showed that Monascus wine fermented by S. cerevisiae TISTR 5169 (W5169) showed the highest result of intensity in cereal, fruit, and alcohol aroma. Therefore, W5169 was selected for subsequent acetous fermentation. During fermentation for 39 days, the titratable acidity (acetic acid) increased, associated with the decrease in alcohol contents and pH values. Acetification increased total phenolic content in accordance with an increase of antioxidant activity. Moreover, Monascus vinegar contained functional ingredients including Monascus pigments; yellow (0.17 OD unit/mL), orange (0.08 OD unit/mL), red (0.06 OD unit/mL), monacolin K (0.0141 ppm), and total phenolic content (71.70 µg GAE/mL). Monascus vinegar exhibited potential for antioxidant activity (58.8%) and xanthine oxidase inhibitory activity (73.7%), and in particular, was without the mycotoxin citrinin.

Synthesis of new anthraquinone compounds and evaluation of their considerable xanthine oxidase inhibitory activities

Synthesis of new anthraquinone compounds and evaluation of their considerable xanthine oxidase inhibitory activities

In Vitro Xanthine Oxidase Inhibitory Activity of Morinda citrifolia L. (Noni) Leaf and Identification of Its Xanthine Oxidase Inhibitors

Hyperuricemia causes an excessive level of uric acid in the body, which leads to the formation of gouty arthritis and high uric acid-related diseases. To cure this condition, xanthine oxidase (XO), a key enzyme in uric acid production, was targeted. A routinely used XO inhibitor drug, allopurinol, has side effects. Therefore, an alternative XO inhibitor with a high activity and fewer side effects is strongly desired. In this research, we evaluated the XO inhibitory activity of Morinda citrifolia L. (noni) leaves extracted using 2 solvents, 95 % ethanol and water. The total phenolic and flavonoid content was analyzed. Moreover, the phenolic profile was investigated using liquid column chromatography-mass spectrometry (LC-MS). The results showed that at a concentration of 100 µg mL−1, the ethanolic (McE) and water (McW) extracts could exhibit XO inhibitory activity above 90 %, and the IC50 values predicted using dose-response logarithmic function curves were 2.24 ± 0.2 and 7.2 ± 0.1 µg mL−1, respectively, while the IC50 of allopurinol was 1.02 ± 0.1 µg mL−1. The total phenolic and flavonoid content in McE was higher than that in McW. LC-MS analysis revealed that all extracts contained several phenolic compounds. Interestingly, known potent XO inhibitors were found in both extracts. Kaempferol, esculetin, saponarin, physcion and g-aminobutyric acid were found in McE, while McW contained esculetin, saponarin and rutin. Taken together, M. citrifolia L. leaves could be used as an effective alternative XO inhibitor for curing hyperuricemia and high uric acid-related diseases caused by XO activity. HIGHLIGHTS The XO inhibitory activity of Morinda citrifolia (noni) leaves was reported for the first time An ethanolic leaf extract (McE) contained higher total phenolic and total flavonoid content than a water extract (McW) Both noni extracts contained the known potent XO inhibitor by kaempferol, esculetin, saponarin, physcion and g-aminobutyric acid were also found in McE, while, McW contained esculetin, rutin, and saponarin GRAPHICAL ABSTRACT

Improving the xanthine oxidase and adenosine deaminase inhibitory activities of Flos Sophorae Immaturus by ultrasound-assisted heating treatments

Flos Sophorae Immaturus (FSI) is consumed as a natural food rich in flavonoids and exhibits potential xanthine oxidase (XOD) and adenosine deaminase (ADA) inhibitory activities. Therefore, ultrasound and heating treatments were applied to improve the XOD and ADA inhibitory effects of FSI, and the mechanisms were revealed by tracking the changes of flavones. Results showed that ultrasound (480 W, 60 min) assisted heating treatments (180 °C, 60 min) significantly improved the XOD (from 40.97% to 83.47%) and ADA (6.64%–23.28%) inhibition rates. Meanwhile, ultrasound and heat treatment caused significant variations in total polyphenols and flavonoid contents and altered the flavonoid composition of FSI. Specifically, rutin, kaempferol–3–o–rutinoside, and narcissoside of FSI converted to quercetin, kaempferol, and isorhamnetin during heating treatments. However, the model experiment revealed that ultrasound treatment did not cause the conversion of flavones and just promoted the dissolution of FSI flavones. Furthermore, quercetin, kaempferol, and isorhamnetin possessed better XOD and ADA inhibitory activities than rutin, kaempferol–3–o–rutinoside, and narcissoside at a concentration from 0.025 mg/mL to 1.0 mg/mL, implying de-glycosylation is a feasible approach for enhancing XOD and ADA activity. The present study provides a promising strategy for the processing of FSI.

Bioactivity and Component Analysis of Water Extract of Sophora japonica against Hyperuricemia by Inhibiting Xanthine Oxidase Activity.

Hyperuricemia (HUA) is a metabolic condition caused by excessive production or low excretion of uric acid (UA) in the body. Xanthine oxidase (XOD) is the key enzyme in the process of metabolism purines to generate UA. In this study, the in vitro inhibitory effect of water extract of the flower bud of Sophora japonica (WESJ) on XOD was investigated by ultraviolet spectrophotometry. A mice model of HUA was constructed to explore the effect of WESJ on UA levels and the mechanism of action on renal function. Based on Box-Behnken design, the optimal extraction process of WESJ was determined to extract Sophora japonica twice with 8 times of water, 0.5 h each time. Pharmacological results showed that low, medium, and high doses of WESJ (200, 400, 600 mg/kg) could significantly reduce serum UA level, inhibit the activity of XOD in blood and liver, and have a protective effect on kidney damage caused by high UA. Through UPLC-Q-TOF-MS/MS analysis, 214 compounds were identified in WESJ, including flavonoids, polyphenols, triterpenoids, organic acids, and others. The rat serum of WESJ was analyzed, and 23 prototype components entering the blood were identified, including 15 flavonoids and polyphenols, which may be the main bioactive components. In conclusion, flavonoids and polyphenols in WESJ may reduce the level of UA and alleviate kidney damage by inhibiting the activity of XOD. WESJ is expected to be used as a plant-based food and dietary supplement for the treatment of HUA.

Stir-frying treatment improves the color, flavor, and polyphenol composition of Flos Sophorae Immaturus tea

Low-temperature drying is the mainstream method of Flos Sophorae Immaturus (FSI) tea processing, while the advantages of stir-frying treatment were illustrated in this study. Herein, the reasons for stir-frying treatment improving the main quality indicators of FSI were clarified by measuring the changes in color difference, flavor, and polyphenol composition during the stir-frying process, as well as the xanthine oxidase inhibitory activity. The results showed that the color of FSI became more attractive after stir-frying at appropriate conditions (160–200 °C for 20–40 min). A total of 75 volatile compounds were identified by GC-MS, and the main volatiles were aldehydes (42.8%) and heterocyclic (16.7%) after stir-frying treatment at 200 ℃ for 20 min, which played a considerable role in the flavor of stir-fried FSI. Meanwhile, the main volatiles of stir-fried FSI tea screened out by the Flash GC E-nose were furaneol, 2-pentylfuran, 3-methylheptane, 3-furaldehyde, 2,5-dimethylfuran, etc. Additionally, the quercetin, kaempferol, and isorhamnetin content gradually increased after stir-frying treatment, which improved the xanthine oxidase inhibitory activity of FSI.

Synthesis, characterization, toxicity evaluation and inhibitory effect of hesperitin-copper (Ⅱ) complex on xanthine oxidase

In this study, a non-toxic hesperitin (Hsp)-Cu(Ⅱ) complex consisting of two Hsp and one Cu2+ was synthesized. The complex showed a significantly higher inhibitory activity against xanthine oxidase (XO) [IC50: (1.07 ± 0.08) × 10−6 mol/L] than Hsp [IC50: (1.17 ± 0.12) × 10−5 mol/L] and Cu2+ [IC50: (4.93 ± 0.21) × 10−6 mol/L], and a decreased antioxidant activity. As a mixed type inhibitor, the complex bound to XO or xanthine-XO complex to inhibit XO activity compared to the competitive inhibitor Hsp that only bound to XO. Both Hsp and Hsp-Cu(Ⅱ) complex statically quenched the endogenous fluorescence of XO, which was driven by hydrophobic interaction and hydrogen bond, and the complex exhibited stronger binding affinity with XO than Hsp. Hsp bound to the molybdopterin (Mo-pt) domain of XO, which tightened the structure of XO and hindered the binding of substrate xanthine to XO, whereas Hsp-Cu(Ⅱ) complex bound near the center of flavin adenine dinucleotide (FAD) with high steric hindrance, resulting in partial unfolding of XO structure. In addition, Cu2+, acting as a bridge for electron transfer, absorbed electrons in the complex, hindered the substrate O2 from gaining enough electrons, and reduces the formation of O2– radicals, thus slowing down the enzymatic reaction and decreasing the activity of XO. These findings may provide new insights into the complex as a promising inhibitor of XO for the prevention and treatment of hyperuricemia.

Xanthine oxidase inhibitory activity of Arcangelisia flava

Background: Hyperuricemia is characterized by elevated levels of uric acid in the blood, produced from its precursor's xanthine and hypoxanthine via xanthine oxidase. Arcangelisia flava, an herbal medicine containing flavonoids, may decrease uric acid levels by inhibiting the xanthine oxidase.
 Objective: This study was to determine the effectiveness of ethanol extracts of A. flava leaves and stems in inhibiting xanthine oxidase. 
 Methods: The leaves and stems of A. flava were extracted using ethanol 96%. Xanthine oxidase activity was measured using UV Vis spectrophotometry and represented as IC50 value. Allopurinol was used as a positive control. 
 Results: The IC50 value of xanthine oxidase inhibitory of ethanol extract of A. flava leaves and stems as well as allopurinol was 174.62, 30.44, 24.03 ppm.
 Conclusion: The stems of A. flava have the activity of lowering uric acid levels better than the leaves.
 

Identification of the roasting reaction products of ferulic and sinapic acids and their xanthine oxidase inhibitory activity.

The roasting reaction products of ferulic and sinapic acids were analyzed using high-performance liquid chromatography (HPLC) and their constituent compounds were isolated. Structural analysis revealed that the major compounds were oligomers of the corresponding 4-vinylphenols. The xanthine oxidase (XO) inhibitory activity of the isolated compounds was also measured. Moderate XO inhibitory activity of some oligomers afforded from ferulic acid was observed.

Evaluation of xanthine oxidase inhibitory, antioxidative activity of five selected Papua medicinal plants and correlation with phytochemical content

Some medicinal plants from Papua have been used traditionally as hyperuricemia and antioxidant agents for many ethnic in Papua Islands. The present study aims to evaluate inhibitory xanthine oxidase, antioxidative activities, total phenolic, and total flavonoid of five Papua selected medicinal plants, Myrmecodia beccarii, Villebrunea rubescens, Breynia cernua, Bridelia spp. and Dodonaea viscosa. Preliminary phytochemical screening revealed the presence of flavonoids and phenolic compounds with TLC-densitometric analysis, which is responsible for the biological activities of different plant extracts. Antioxidant was tested by 2,2- diphenyl-1- picrylhydrazyl (DPPH) and cupric ion antioxidant capacity (CUPRAC) methods and expressed as the Antioxidant Activity Index (AAI). Xanthine oxidase inhibitory (XOI) activity was evaluated by a spectrophotometer. The ethyl acetate of Myrmecodia beccarii extract (MEA) showed the highest antioxidative and XOI activity. The MEA extract from Papua may be developed as a new potential source of antioxidant and xanthine oxidase inhibitory agent.

Medicinal fungus Phellinus igniarius alleviates gout in vitro by modulating TLR4/NF-kB/NLRP3 signaling.

Background: Phellinus igniarius (P. igniarius) is a valuable medicinal and edible fungus with various biological activities such as anti-inflammation, antioxidation, and immune regulation. In this study, we explored the effects of P. igniarius on a gout model in vitro. Methods: The DPPH, ABTS, and FRAP methods were combined to determine and compare the antioxidant activities of wild P. igniarius total polyphenols (WPP) and cultivated P. igniarius total polyphenols (CPP) in vitro. Spectrophotometry was used to compare the inhibitory effect of WPP and CPP on xanthine oxidase (XO) activity to evaluate anti-hyperuricemia activity in vitro. HUVECs were stimulated with monosodium urate (MSU) crystals for 24h to establish an acute gouty inflammation model in vitro. The protective effects were compared by measuring cell viability; the contents of ICAM-1, IL-1β, IL-6 and VCAM-1; the protein expressions of TLR4 and NLRP3; reactive oxygen species production; and the nuclear translocation of NF-κB p65. UHPLC-QE-MS technology was used to explore the potential metabolic mechanism of P. igniarius against gout. Results: WPP and CPP had strong antioxidant capacity, and the antioxidant capacity of CPP was similar to that of WPP. In a comparative experiment of xanthine oxidase activity inhibition by WPP and CPP, the IC50 values were 88.19μg/ml and 108.0μg/ml, respectively. At a dose of 40μg/ml, WPP and CPP significantly improved the decrease in cell viability induced by monosodium urate (150μg/ml) and inhibited the increase in inflammatory factors such as ICAM-1, IL-1β, IL-6, and VCAM-1. The increase in TLR4 and NLRP3 protein expression induced by MSU crystals in HUVECs was also significantly inhibited by total polyphenols from wild and cultivated P. igniarius. In addition, both significantly improved MSU-induced ROS overproduction and NF-κB p65 nuclear translocation. WPP and CPP may primarily be involved in phenylalanine metabolism and lysophosphatidylcholine metabolism in their role in the treatment of gout. Conclusion: CPP and WPP both showed good antioxidant activity and xanthine oxidase inhibitory activity and had good therapeutic effects on the gout model in vitro. Furthermore, this study indicated that cultivated P. igniarius had a protective effect similar to that of wild P. igniarius, which would be expected to improve the shortage of wild P. igniarius and promote the development of the cultivated P. igniarius industry and product development.

Exploration, sequence optimization and mechanism analysis of novel xanthine oxidase inhibitory peptide from Ostrea rivularis Gould

Xanthine oxidase (XO) inhibitory peptides are secure and efficient functional food ingredients for treating or alleviating hyperuricemia (HUA). In this study, ultrafiltration and molecular exclusion chromatography were used to separate and purify enzymatic lysate of oyster protein, three novel peptides (ALSGSW, GGYGIF and MAIGLW) with strong XO inhibitory activity were screened by LC-MS/MS identification and molecular docking technology. Then, the mechanism of action between peptides and the XO was revealed by molecular docking technology, and the structure of the peptide was rationally designed on this basis. The results showed that replacing N-terminal Gly of peptide GGYGIF with Trp can significantly improve its XO inhibition rate, and peptides formed by the simple structure amino acid was connected to the aromatic amino acids has preferable inhibitory activity. These results showed that oyster was a good source of XO peptide inhibitors, molecular docking technology was an effective tool for obtaining highly active peptides.

Process Optimization Based on Biological Effects and Biomarker Contents of Camellia japonica L. for the Development of Anti-Hyperuricemic and Anti-Wrinkle Source

The purpose of this study was to simultaneously develop anti-hyperuricemic and anti-wrinkle source using Camellia japonica leaf (CJ). CJ extract was prepared. Its contents of biomarkers and biological activities were then analyzed. First, we investigated the extraction efficiency. The extraction rate was 10% or less with hot water or 80% ethanol. HPLC analysis revealed that CJ extract contained rutin, hyperoside, isoquercitrin, chlorogenic acid (CGA), gallocatechin gallate (GCG), and phillygenin. As a result of measuring contents of biomarkers in the extract, CGA was detected in 20, 40, and 60% ethanol extracts. GCG showed the highest content in the hot water extract. Hyperoside and isoquercitrin showed the highest contents in the 80% ethanol extract. Philligenin showed an even content of 0.1% or more in all samples except for 40% ethanol extract. Rutin showed the highest content in 80% ethanol extract. Elastase inhibitory abilities of six extracts and PPRM were investigated at a concentration of 0.5 mg/mL. Results revealed that PPRM and 80% ethanol extract showed about 80% and 62% inhibition, respectively. As a result of comparing elastase inhibitory activities of biomarkers, hyperoside, isoquercitrin, and philligenin showed higher activities. Among six extracts, the extract that could be used as an anti-hyperuricemic source was 80% ethanol extract. When xanthine oxidase (XO) inhibitory activities of biomarkers were evaluated, rutin and hyperoside showed excellent activities. In particular, when XO activity was measured by mixing rutin and hyperoside with 80% ethanol extract, the same efficacy as 80% ethanol extract was obtained. It was predicted that 80% ethanol extract could be used simultaneously as an anti-hyperuricemic and anti-wrinkle source. Further studies are needed to determine anti-hyperuricemic activities of rutin and hyeproside in vivo.

Hydrothermal treatment improves xanthine oxidase inhibitory activity and affects the polyphenol profile of Flos Sophorae Immaturus.

Flos Sophorae Immaturus (FSI) is rich in polyphenols and a potential uric acid-lowering food. However, the processing of FSI is greatly restricted due to the heat sensitivity and low solubility of polyphenols. In this study, hydrothermal treatment - an effective strategy - was applied to FSI processing. The variation of xanthine oxidase (XO) inhibitory effect and polyphenol composition of FSI during hydrothermal treatment were recorded. The XO inhibition rate of FSI increased from 32.42% to 89.00% after hydrothermal treatment at 220 °C for 30 min, as well as total polyphenols (from 0.66 to 1.11 mg mL-1 ) and flavonoids (from 1.21 to 1.58 mg mL-1 ). However, high thermal temperature (>160 °C) and extended thermal time (>90 min) caused the degradation of polyphenols. Rutin, kaempferol-3-O-rutinoside and narcissoside rapidly degraded and converted to quercetin, kaempferol and isorhamnetin when the temperature exceeded 160 °C. The maximum yields of quercetin, kaempferol and isorhamnetin were at 220 °C for 30 min, 90 min and 90 min, respectively. Meanwhile, the conversion kinetics conformed to the first-order model. Interestingly, these newly formed polyphenols possessed better XO inhibitory effects than their derivatives with 3-O-rutinoside. Polyphenol conversion during hydrothermal treatment was the main reason for enhancing XO inhibitory activity. Therefore, hydrothermal treatment is an appropriate method for improving the XO inhibitory effect of FSI. © 2022 Society of Chemical Industry.

Identification, inhibitory mechanism and transepithelial transport of xanthine oxidase inhibitory peptides from whey protein after simulated gastrointestinal digestion and intestinal absorption

In the present study, xanthine oxidase (XO) inhibitory peptides were identified from peptides that survived in whey protein isolate (WPI) simulated gastrointestinal digestion and passed through the Caco-2 cell monolayer, and their inhibitory mechanism and transepithelial transport were investigated. After in silico screening and activity validation, PEW and LLW showed the highest XO inhibitory activity with 50 % inhibitory concentrations (IC50) of 3.46 ± 0.22 and 3.02 ± 0.17 mM, respectively. Molecular docking, molecular dynamics simulation, and circular dichroism (CD) results revealed that these two peptides could interact with the residues in the XO active cavity via hydrogen bonds and hydrophobic forces to form a more stable protein-ligand complex, thus affecting the binding of the substrate to XO. Furthermore, PEW and LLW were transported across Caco-2 cell monolayers intact through the paracellular route and peptide transporter 1 (PepT1), and tight junction proteins zonula occludens 1 (ZO-1) and occludin were not disrupted by PEW and LLW. This study suggests that PEW and LLW potentially regulate XO activity in vivo to exert antihyperuricemia effects.