Cytotoxic biflavonoids from Selaginella delicatula

Four new biflavonoids-robustaflavone 4'-methyl ether (1), robustaflavone 7, 4'-dimethyl ether (2), 2 ",3 "-dihydrorobustaflavone 7,4', -dimethyl ether (3), and 2 ",3 "-dihydrorobustaflavone 7,4', 7 "-trimethyl ether (4)-as wel l as two known biflavonoids, robustaflavone and amentoflavone, and three ca ffeoylquinic acids, 3,5-di-O-caffeoylquinic acid, 3,4-di-O-caffeoylquinic a cid, and 4,5-di-O-caffeoylquinic acid, were isolated from Selaginella delic atula. The structures of the new compounds were established by spectroscopi c analysis and chemical modification. The cytotoxic activity of these compo unds on various tumor cell lines was evaluated, and both compounds 1 and 3 significantly suppressed the growth of Raji and Calu-1 tumor cell lines.