Prenylated 4-phenylcoumarins and 4-alkylcoumarins from Kielmeyera argentea and their cytotoxic activity.

Two new prenylated 4-phenylcoumarins, named kielcoumarin A (1) and kielcoumarin B (2) together with three known compounds, mammea B/BA (3), mammea B/BA cyclo F (4) and ferruol A (5), were obtained from stems and roots of Kielmeyera argentea (Calophyllaceae). Their structures were elucidated based on spectroscopic data. Cytotoxic activity of the 4-alkylcoumarins 3-5 was evaluated in vitro against human U251 glioblastoma cell line. Compound 3 showed significative activity with EC50 value of 6.6 µM while compounds 4 and 5 showed respective EC50 values of 52.0 and 37.0 µM.