Inhibition of xanthine oxidase by orientin, a C-glycosylated flavonoid: Kinetic characterization and molecular simulation

Orientin inhibited xanthine oxidase with moderate in vitro potency. • Global kinetic fitting supported a mixed-type inhibition mechanism. • Fluorescence quenching verified direct XO–orientin interaction. • Molecular simulations indicated a stable XO–orientin binding mode. • C-glycosylation altered ADMET-related properties versus luteolin. Xanthine oxidase catalyzes the oxidation of hypoxanthine to xanthine. It further oxidizes xanthine to uric acid, making it an important target for treating hyperuricemia. This study focused on orientin as a model flavonoid for xanthine oxidase inhibition. We examined whether the C-glycosyl group changes its inhibitory potency, binding pattern, and predicted ADMET profile. In vitro enzyme activity was determined to be 364.79 ± 8.21 μM for the half-inhibitory concentration (IC 50 ) of orientin. Kinetic analysis suggested a mixed-type inhibition pattern. Intrinsic fluorescence quenching further supported the interaction between orientin and XO. Molecular docking and molecular dynamics simulations provided structural insight into the binding mode and stability of the orientin–XO complex. ADMET analysis indicates that orientin has promising pharmaceutical properties. These findings provide a basis for future research focusing on structural optimization, metabolic transformation, and in vivo evaluation. Download: Download high-res image (385KB) Download: Download full-size image