Cytotoxicity of withanolides isolated from Acnistus arborescens.

A new withanolide identified by spectroscopic analysis as 12beta-acetoxy-4-deoxy-5,6-deoxy-Delta(5)-withanolide D and Withanolide D, were isolated from the leaves of Acnistus arborescens. Cytotoxic activity of these two compounds against human tumor cell lines HT-29, MCF-7, MKN-45, HEp-2, HeLa, U-937 and two human normal fibroblast cultures, Fib04 and Fib05, were assessed. Withanolide D presented in vitro cytotoxic activity against tumor cell lines at the low micromolar range (LC(50):1.0 to 1.69 microM) and showed a slightly lower activity against Fib04, suggesting moderated selectivity among tumoral and normal cells. No cytotoxic effect was observed for 12beta-acetoxy-4-deoxy-5,6-deoxy-Delta(5)-withanolide D.