Insights into the inhibitory mechanism of purpurogallin on xanthine oxidase by multiple spectroscopic techniques and molecular docking

•Purpurogallin exhibits a potent inhibitory activity on xanthine oxidase (XO).•Purpurogallin reversibly inhibits XO in a mixed type manner.•Purpurogallin quenches the fluorescence of XO through a static quenching procedure.•The binding of purpurogallin to XO induces changes in the secondary structure of XO.•Molecular docking reveals that purpurogallin mainly binds to molybdenum atomic domain.