Bioactive sesquiterpene lactones and other compounds isolated from Vernonia cinerea

Four new sesquiterpene lactones, 8 alpha-(2'Z-tigloyloxy)-hirsutinolide (1), 8 alpha-(2'Z-tigloyloxy)-hirsutinolide-13-O-acetate (2), 8 alpha-(4-hydroxytigloyloxy)-hirsutinolide (3), and 8 alpha-hydroxy-13-O-tigloyl-hirsutinolide (4), along with seven known derivatives (5-11), three norisoprenoids (12-14), a flavonoid (15), and a linoleic acid derivative (16), were isolated from the chloroform partition of a methanol extract from the combined leaves and stems of Vernonia cinerea. Their structures were established by 1D and 2D NMR, UV, and MS analyses. Compounds 1-16 were evaluated for their inhibitory effects against the viability of U251MG glioblastoma and MDA-MB-231 breast cancer cells that harbour aberrantly-active STAT3, compared to normal NIH3T3 mouse fibroblasts that show no evidence of activated STAT3. Among the isolates, compounds 2 and 7 inhibited the aberrant STAT3 activity in glioblastoma or breast cancer cells. Further, compounds 7 and 8 inhibited viability of all three cell lines, compounds 2,4, and 9 predominantly inhibited the viability of the U251MG glioblastoma cell line. (C) 2014 Elsevier B.V. All rights reserved.