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

Myricetin, a plant-derived flavonol, was found to inhibit the formation of uric acid in a mixed-type manner with IC50 value of (8.66±0.03)×10-6molL-1 and more potently inhibit the generation of superoxide anion (O2-) catalysed by xanthine oxidase (XOD) with IC50 value of (4.55±0.02)×10-6molL-1. Inhibiting O2- generation by myricetin may be attributed to the reduced form of XOD with a substantially higher reduction potential for FADH/FADH2 couple. Moreover, molecular docking verified that myricetin bound to the site around isoalloxazine ring in the flavin adenine dinucleotide (FAD) domain to block the diffusion of O2- out of the FAD site, resulting in the transfer of another electron from FADH2 to O2- to form hydrogen peroxide. This study has provided new insight into the role of myricetin in inhibiting XOD catalysis, which may be beneficial to improve myricetin's potential application in functional foods.