Bioactive compounds from the roots of Strophioblachia fimbricalyx
Eight new compounds, fimbricalyxs B–D (1–3), fimbricalyxanhydrides A and B (4, 5), and fimbricalyxlactones A–C (6–8), together with three known compounds, trigonostemone (9), 3,6,9-trimethoxyphenanthropolone (10), and fimbricalyx A (11), were isolated from the roots of Strophioblachia fimbricalyx. The structures of the new compounds were elucidated on the basis of their spectroscopic data and, in the case of compounds 2, 4, and 7, confirmed by single-crystal X-ray crystallographic analysis. Compounds 1–4 and 8 were evaluated for their cytotoxicity (KB, MCF7, and NCI-H187 cancer cells) and antiplasmodial activity (Plasmodium falciparum, K1 multidrug-resistant strain). Fimbricalyx B (1) exhibited potent antiplasmodial activity with an IC50 value of 0.019 μM, while 4 was cytotoxic toward NCI-H187 cancer cells and showed antiplasmodial activities with IC50 values of 5.7 and 3.9 μM, respectively. In addition, the X-ray structure of 10 and the antiplasmodial activity of 11 are reported herein for the first time.