Pyrogallol is a key component for xanthine oxidase inhibition by the leaves of Ammannia baecifera

Abstract

Ammannia baecifera Linn is an important plant in traditional medication system of Bangladesh. In order to give the scientific clarification for using this plant in the treatment of gout, this study was designed to identify the xanthine oxidase (XO) inhibitors present in the extract of Ammannia baecifera leaves along with evaluating its antioxidant effect. First aqueous extract was prepared from leaves and then water insoluble part (WIP) was separated from water soluble part (WSP) as precipitate with ethanol. In DPPH and ABTS assays, WSP with rich amount of phenolic compound exhibited high radical scavenging activity than WIP. WSP also showed potent XO inhibition with IC50: 18.03 ± 1.65 μg/mL value. Using different chromatographic techniques, the key XO inhibitor was isolated from WSP and identified as pyrogallol based on its different spectroscopic data. In XO inhibition assay, pyrogallol (IC50: 11.67 ± 0.45 μg/mL) showed potent inhibitory effect as compared to a known XO inhibitor (allopurinol; IC50 = 27.35 ± 1.15 μg/mL) and it also displayed strong DPPH and ABTS radical scavenging effect. In addition, an inhibition kinetics study indicated that WSP and pyrogallol are mixed competitive inhibitors of XO. The overall results suggest that the presence of pyrogallol as XO inhibitor and free radical scavenger in Ammannia baecifera leaf justifies the traditional uses of this plant.
 Keywords: Ammannia baecifera, Leaves, Xanthine oxidase, Pyrogallol, Inhibitor