Structure of constituents isolated from the bark of Cassipourea malosana and their cytotoxicity against a human ovarian cell line

Three aromatic compounds, 2α,3α-epoxyflavan-5,7,4′-triol-(4β → 8)-afzelechin (1), 2β,3β-epoxyflavan-5,7,4′-triol-(4α → 8)-epiafzelechin (2), and methyl 4-ethoxy-2-hydroxy-6-propylbenzoate (3), as well as eight known compounds (4–11) were isolated from the bark of Cassipourea malosana (Rhizophoraceae). Their structures were determined on the basis of an analysis of spectroscopic data. The in vitro cytotoxic activities of these compounds against human ovarian cancer cell line TOV21G were evaluated. Most compounds showed little activity; however, the methyl derivatives of flavan dimers (1a and 2a) showed higher activity (IC ₅₀ value of 30.3 and 75.4 μM) than parent compounds 1 and 2.