Delphinidin-3-O-sambubioside: A novel xanthine oxidase inhibitor identified from natural anthocyanins

Abstract

Objectives: This study was conducted to investigate the xanthine oxidase (XO) inhibitory activities of 18 monomeric anthocyanins from berry fruits and roselle, and to illustrate the underlying mechanism of the most active anthocyanin delphinidin-3-O-sambubioside. Materials and Methods: Eighteen monomeric anthocyanins were prepared and purified in our laboratory. The inhibitory properties of anthocyanins were investigated by in vitro inhibitory activity studies and fluorescence quenching studies; the inhibitory mechanism was explored through kinetic studies, fluorescence quenching studies, circular dichroism analysis and computational docking simulations. Results: XO inhibitory activities of anthocyanins were related to the structures of B rings and glycosides. Among all the tested anthocyanins, delphinidin-3-O-sambubioside showed the most potent inhibitory activity with an IC50 of 17.1 μM, which was comparable to the positive control allopurinol. Spectroscopic results revealed that delphinidin-3-O-sambubioside could spontaneously interact with XO and induce conformational changes. Computational docking study indicated that delphinidin-3-O-sambubioside could bind to XO with a proper orientation, stably formed π-πinteractions and hydrogen bonds with key residues, thus preventing the substrate from entering the active pocket. Conclusions: In brief, our study identified delphinidin-3-O-sambubioside as a potent XO inhibitor from natural anthocyanins, which is potentially applicable for prevention and treatment of hyperuricemia.