Jacaranone analogs from Senecio scandens.

Bioassay-guided fractionation of the ethanolic extract of Senecio scandens led to the isolation of four new compounds 4, 5, 7, and 8, along with four known jacaranone analogs (1, 2, 3, 6). Their structures were elucidated on the basis of spectral and chemical evidence. Compound 7 was obtained as a tautomeric mixture of alpha/beta-epimer. The cytotoxic activities of these compounds were evaluated. Among these, compounds 5 and 8 showed potent cytotoxicities. The benzoquinone derivative, jacaranone ethyl ester (1), was the major cytotoxic constituent in this plant with IC(50)s at a range of 0.5-1.0 microg/ml against various tumor cell lines. The SAR of these jacaranone analogs (1-8), isolated from S. scandens, was also discussed.