Xanthine Oxidase Inhibitory Mechanism of Fisetin and Hesperitin

Fisetin and hesperitin are two common flavonoids in plant medicines. In this paper, the mechanism of xanthine oxidase (XO) inhibition was systematically studied by combining experimental and theoretical methods. The HPLC results suggested that the XO inhibitory activity of fisetin (IC50, 0.140 mM) was superior to that of hesperitin (IC50, 0.635 mM). The spectrofluorimetry results showed flavonoids could induce the static fluorescence quenching of XO, indicating that they played the inhibitory activity by forming the complexes with XO. We showed the paramount force of fisetin and XO was hydrophobic; in the complex of hesperidin and XO, hydrogen bonding and van der Waals force were crucial forces. We used Autodock software for molecular docking. The results suggested that both fisetin and hesperitin entered the active pocket of XO, and the complexes were maintained by hydrogen bonding and hydrophobic interaction, which coincided with the experimental results.