Chemical evidence for potent xanthine oxidase inhibitory activity of Glechoma hederacea var. grandis leaves (kakidoushi-cha).

In this study, chemical evidence for the potent xanthine oxidase inhibitory activity of "kakidoushi-cha" (dry leaves of Glechoma hederacea var. grandis), a traditional folk tea consumed in Japan, was clarified on the basis of structure identification of the active constituents. Assay-guided fractionation and purification afforded 15 compounds from the most active chromatographic fraction of an extract of the tea. Two flavonoids, apigenin and luteolin, showed remarkable inhibitory activity against xanthine oxidase (XO). The contribution of these flavonoid constituents to the observed XO inhibitory activity of the methanol and boiling-water extracts of the tea was estimated to be ca. 35% and ca. 18%, respectively.