Sesquiterpene lactones from two newly-described species of Vernonia: V. jonesii and V. pooleae

Two novel, non-glaucofide, germacrolide sesquiterpene lactones, 8α-methacryloyloxycostunolide-1(10),4(5)-diepoxide and 1-oxo-10α-OH-8α-methacryloyloxycostunolide (not fully characterized), were isolated from Vernonia jonesii and the previously described glaucolide B was identified from V. pooleae. This is one of the few reports of non-glaucolide type germacrolides in a New World species of Vernonia, although members of this class of sesquiterpene lactones are common constituents of Old World species of the genus. The chemical evidence supports the suggestion that V. jonesii may be part of a relictual, isolated group of the New World Vernonia, closely related to some of the Old World taxa.