Bioaffinity ultrafiltration combined with UPLC-ESI-QTrap-MS/MS for screening of xanthine oxidase inhibitors from Paederia foetida L. leaves

Paederia foetida L. leaf (PFL) is recognized for its uric acid-lowering potential. However, the key compounds and their mechanisms of countering hyperuricemia remain unclear. In this study, bioaffinity ultrafiltration in combination with UPLC-ESI-QTrap-MS/MS was used to screen and identify potential xanthine oxidase (XO) inhibitors in the PFL extract, and the possible mechanisms of their interaction were investigated by molecular docking. The experimental results showed that the PFL extract exhibited excellent antioxidant and anti-XO effect. Further the results of enzyme inhibition experiments in vitro showed that luteolin-7-O-glucoside (IC50 = 61.41 μg/mL), astragalin (IC50 = 114.89 μg/mL), quercitrin (IC50 = 124.50 μg/mL), dihydromyricetin (IC50 = 296.32 μg/mL), cyanidin-3-O-rutinoside (IC50 = 373.82 μg/mL), kaempferol-3-O-rutinoside (IC50 = 450.10 μg/mL) and (-)-epigallocatechin (IC50 = 610.48 μg/mL) in PFL extracts were the major contributors to the XO inhibitory activity, and confirmed this finding. Molecular docking revealed these inhibitors interact with critical XO residues through hydrogen bonding, hydrophobic, and electrostatic interactions, highlighting flavonoids in PFL extracts as potent XO inhibitors. This work provides insight into flavonoids in the PFL extracts as potent XO inhibitors.