Bioassay-guided fractionation of a solid tumor selective extract of the leaves and twigs of Antheroporum pierrei acquired from the U.S. National Cancer Institute extract repository afforded four new pyranoisoflavones, pierreiones A-D (1-4), together with rotenone (5), 12a-hydroxyrotenone (6), and tephrosin (7). The structures of all new compounds were determined on the basis of their spectroscopic data, and the absolute configuration of 1 was assigned with the help of (1)H NMR analysis of its Mosher's ester derivatives. Compounds 1 and 5-7 accounted for the majority of the biological activity in terms of either cytotoxicity and/or selective toxicity to solid tumor cell lines. Pierreiones A (1) and B (2) demonstrated solid tumor selectivity with minimal cytotoxicity, while pierreione C (3) exhibited no activity.
