Cytotoxic and antiplasmodial compounds from the roots of Strophioblachia fimbricalyx.

The known phenanthrenone trigonostemone (1), along with a new phenanthrenone, 9-O-demethyltrigonostemone (2), and two new phenanthropolones, 3,6,9-trimethoxyphenanthropolone (3) and 4,6,9-trimethoxyphenanthropolone (4), were isolated from the roots of Strophioblachia fimbricalyx. Compound 2 showed cytotoxicity against NCI-H187, KB, and MCF7 cancer cells with IC50 values of 0.8, 0.8, and 2.9 microg/mL, respectively, while 3 and 4 showed reduced cytotoxicity. Compounds 2 and 3 displayed antiplasmodial activity in vitro (IC50 values of 2.7 and 3.2 microg/mL, respectively) against Plasmodium falciparum (K1, resistant strain). In addition, the antioxidant activity of 1-4 toward DPPH radicals was determined, but only compound 2 showed any discernible activity.