Xanthine oxidase inhibitors from Brandisia hancei

Xanthine oxidase is a key enzyme associated with the incidence of hyperuric emia-related disorders. Repeated chromatography of the enzyme inhibitory pa rt of the water extract of the twigs and leaves of Brandisia hancei (Scroph ulariaceae) gave a flavone luteolin, an iridoid glycoside mussaenoside, two beta-sitosterol glycosides daucosterol and beta-sitosterol gentiobioside, and five phenylethanoids arenarioside, brandioside, acteoside, 2'-O-acetyla cteoside and isoacteoside. Luteolin and isoacteoside inhibited the xanthine oxidase (XO, EC 1.2.3.2) with the IC50 values at 7.83 and 45.48 mu M, resp ectively. Isoacteoside was found to be the first phenylethanoid that decrea sed substantially the formation of uric acid by inhibiting competitively xa nthine oxidase (K-i value: 10.08 mu M). Furthermore, the study suggested th at the caffeoylation of the 6'-hydroxyl group of the phenylethanoids was es sential for the enzyme inhibitory action.