Cytotoxic withanolides from Tubocapsicum anomalum.

Fifteen new withanolides (1-8, 11-17) and two known withanolides, withanolide D (9) and 17alpha-hydroxywithanolide D (10), were isolated from the stems, roots, and leaves of Tubocapsicum anomalum using bioassay-directed fractionation. The structures were determined by spectroscopic and chemical methods, and the absolute configurations were established by CD analysis and by the Mosher ester method. The structure of 1 and 3 were further confirmed by X-ray crystallographic analysis. Compounds 1, 4-6, 8-10, and 13 showed significant cytotoxic activity against Hep G2, Hep 3B, A-549, MDA-MB-231, MCF-7, and MRC-5 cell lines.