Cytotoxic cardiac glycosides and coumarins from Antiaris toxicaria.

Eight new cardiac glycosides/aglycones (antiaritoxiosides A-G, 1-7, and antiarotoxinin B, 8), two new coumarins (anticarins A-B, 41-42), and two new flavanones (antiarones L-K, 43-44) were isolated from trunk bark of Antiaris toxicaria together with 53 known compounds. The new structures were established by extensive analysis of spectroscopic data. Compound 1 (10-carboxy and 3α-hydroxy) and compounds 3-6 (10-hydroxy) contain unique substituents that are rarely found in cardiac glycosides. The cytotoxic effects of isolated compounds against ten human cancer cell lines, KB, KB-VIN, A549, MCF-7, U-87-MG, PC-3, 1A9, CAKI-1, HCT-9 and S-KMEL-2, were tested using the sulforhodamine B assay. Five compounds (12, 16, 20, 22, and 31) showed significant cytotoxicity against all ten cancer cell lines, with notable potency at the ng/mL level against some cell lines, which merits further development as clinical trial candidates.