Ashwagandhanolide, a bioactive dimeric thiowithanolide isolated from the roots of Withania somnifera.

A new dimeric withanolide, ashwagandhanolide (1), was isolated from the roots of an Ayurvedic medicinal herb, Withania somnifera. A detailed spectroscopic evaluation revealed its identity as a dimer with an unusual thioether linkage. Compound 1 displayed growth inhibition against human gastric (AGS), breast (MCF-7), central nervous system (SF-268), colon (HCT-116), and lung (NCI H460) cancer cell lines, with IC50 values in the range 0.43-1.48 microg/mL. In addition, it inhibited lipid peroxidation and the activity of the enzyme cyclooxygenase-2 in vitro.