New flavonol glycosides and new xanthone from Polygala japonica

Three new flavonol glycosides and a new xanthone were isolated from Polygala japonica HOUTT. with eight known compounds. Their structures were identified as 1,7-dihydroxy-3,4-dimethoxy-xanthone (1), kaempferol-7,4'-dimethyl ether (2), physcion (3), guazijinxanthone (4), rhamnetin (5), polygalin A (6), 3,5,7-trihydroxy-4'-methoxy-flavone-3-O-beta-d-galactopyranoside (7), 3,5,3'-trihydoxy-7,4'-dimethoxy-flavone-3-O-beta-d-galactopyranoside (8), 3,5,3',4'-tetrahydroxy-7-methoxy-flavone-3-O-beta-d-galactopyranoside (9), 3,5,3',4'-tetrahydroxy-7-methoxy-flavone-3-O-beta-d-glucopyranoside (10), polygalin B (11), polygalin C (12). Among them, compound 4 is a new xanthone, and 6, 11 and 12 are new flavonol glycosides. Compounds 1, 4, 7 and 8 were tested for cytotoxic activity with MTT assays on five human tumor cell lines, K562, A549, PC-3M, HCT-8 and SHG-44. Compound 4 showed cytotoxic activity against all the five cell lines.