Artaboterpenoids A and B, Bisabolene-Derived Sesquiterpenoids from Artabotrys hexapetalus

Artaboterpenoids A and B (1 and 2), two novel bisabolene-derived sesquiterpenoids, were isolated from the roots of Artabotrys hexapetalus. Their structures with absolute configurations were elucidated by spectroscopic methods, and electronic circular dichroism (ECD) analyses. Notably, 1 featured a novel carbon skeleton with a new C-2-C-10 linkage, and 2a and 2b, a pair of enantiomers, represented the first examples of 1,2-seco-bisabolene-type sesquiterpene lactones. 2a exhibited cytotoxic effects against HCT-116, HepG2, A2780, NCI-H1650, and BGC-823 cell lines with IC50 values of 1.38-8.19 mu M. Plausible biogenetic pathways for artaboterpenoids A and B were proposed.