New sesquiterpene lactones, vernonilides A and B, from the seeds of Vernonia anthelmintica in Uyghur and their antiproliferative activities

A new guaianolide sesquiterpene lactone, vernonilide A (1), and a new elemanolide sesquiterpene lactone, vernonilide B (2), were isolated from the seeds of Vernonia anthelmintica, together with three known elemanolide sesquiterpene lactones (3–5). The structures of the isolated compounds were elucidated on the basis of physicochemical evidences. Compounds 1, 3, and 4 showed strong antiproliferative activities against three human cancer cell lines (A549, HeLa, and MDA-MB-231), with IC₅₀values ranging from 0.10 to 1.00 μM. In addition, 5 exhibited significant antiproliferative activities against HeLa and MDA-MB-231 cells, with IC₅₀values ranging from 1.90 to 2.20 μM. The antiproliferative activities of the acetyl derivatives 6 and 7 prepared from 4 and 3, respectively, against the three cell lines were 4–10-fold weaker than the original activities.