Background: Xanthine oxidase (XO) enzyme inhibitors are used to treat hyperuricemia. Certain natural substances have been reported to be strong inhibitors of xanthine oxidase. The purpose of this study was to evaluate the antioxidant activity and XO inhibition effect of ethanolic extract from mulberry leaves.
Methods: The chemical composition of Mulberry leaf ethanolic extract (MLEE) was identi- fied by the LC-MS/MS method. Antioxidant activity was measured by three different assays (i.e. superoxide, hydrogen peroxide, and hydroxyl radicals assays). The inhibitory effect on XO and its inhibitory mechanism were investigated through the testing of inhibition kinetics and inhibition rate.
Results: MLEE showed significant antioxidant activity in the superoxide, hydrogen peroxide, and hydroxyl radicals assays (IC50 of 0.33 ±0.006 mg/mL, 45 ±0.8 μg/mL, and 2.54 ±0.05 mg/mL for each assay respec- tively). The effects of XO inhibitory activity showed that MLEE was a reversible and competitive inhibitor with IC50 values of 1104.76 ±7.1 μg/mL. Eleven compounds, including six flavonoids and five phenolic acids, were identified.
Conclusions: MLEE has been shown to exhibit antioxidant activity and XO inhibitory effect, which provides a new insight into the properties of mulberry leaves and their potential future applications as a natural anti- gout drug.
Keywords: LC-MS/MS; antioxidant; mulberry leaves; xanthine oxidase.