Xanthine oxidase inhibitors from the flowers of Chrysanthemum sinense

From the MeCH extract of the flowers of Chrysanthemum sinense, a new flavone glucoside, acacetin 7-O-(3-O-acetyl-beta-D-glucopyranoside) (1), has been isolated together with 27 known compounds including flavonoids, caffeoylquinic acid derivatives, phenolics, and a monoterpenoid glucoside. Their structures were elucidated on the basis of spectroscopic data. Compounds 1 - 15, 20 - 24, and 27 displayed significant xanthine oxidase inhibitory activity in a concentration-dependent manner, and compounds 2-11 and 22 showed more potent inhibitory activity, with IC50 values ranging from 0.13 to 2.31 mu M, than that of a positive control allopurinol (IC50 = 2.50 mu M). The kinetic study indicated that 1 - 15 and 20 - 24 displayed competitive-type inhibition like that of allopurinol, while 27 displayed a mixed-type inhibition.