Two new dioxyxanthones, polyhongkongenoxanthones A and B(1 and 2) were isolated from the herbs of Polygala hongkongensis, together with six known xanthones. Their structures were elucidated on the basis of chemical and spectroscopic evidence. The isolates were tested for their cytotoxicity against three tumor cell lines(HepG2, GLC-82 and MCF-7, HepG2=human hepatocellular carcinoma cells; GLC-82=human lung carcinoma cells; MCF-7= human breast carcinoma cells) by MTT assay, among which polyhongkongenoxanthone B(2), 1,7-dihydroxy-2,3- methylenedioxyxanthone(3) and 1,7-dihydroxy-3,4,8-trimethoxyxanthone(6) are potential antitumor candidate due to their significant cytotoxic effects on the three cell lines..
