Study on the interaction mechanism between luteoloside and xanthine oxidase by multi-spectroscopic and molecular docking methods.

Gout is an inflammatory joint disease caused by urate crystal deposition, which is associated with hyperuricemia. Gout will take place when the uric acid accumulates. Xanthine oxidase (XO) is a crucial enzyme in the formation of uric acid. Inhibiting XO is one of the means to ameliorate gout. Luteoloside is a kind of natural flavonoid, which has an excellent prospect for relieving gout. But there are few reports on the interaction mechanism between luteoloside and XO currently. In this study, the interaction mechanism between luteoloside and XO was explored using spectroscopy and molecular docking. The fluorescence spectroscopy results indicated that luteoloside could make the intrinsic fluorescence of XO quenched, and the binding constant between luteoloside and XO was (1.85 ± 0.22) × 103  L mol-1 at 298 K. The synchronous fluorescence spectroscopy results showed that the absorption peaks of Tyr and Trp shifted blue, and the hydrophobicity of the microenvironment increased. Moreover, CD spectra showed that α-helix of XO decreased, β-sheet and β-turn increased after adding luteoloside. The results of molecular docking analysis showed that XO could combine with luteoloside through hydrogen bonds and hydrophobic force. The results indicated that luteoloside could remarkably interact with XO. Insights into the interaction mechanism provide a necessary basis for the search for low-toxic natural products as targets of XO. HIGHLIGHTS: Luteoloside and xanthine oxidase was a strong binding mode and had only one binding site. Luteoloside could cause α-helix reduced, β-sheet and β-turn increased, and change the secondary structure of XO. The binding between luteoloside and xanthine oxidase was a spontaneous process. The main binding force was hydrophobic force between luteoloside and xanthine oxidase.