Vernonolide A, a Sesquiterpene Lactone with a Unique Carbon Skeleton from

A novel sesquiterpene lactone derivative, vernonolide A (), featuring an unprecedented carbon skeleton, along with its plausible biosynthetic precursor, vercinolide I (), and eight known sesquiterpene lactones (-) were isolated and characterized from the whole plants of (L.). The structures of and were elucidated using nuclear magnetic resonance spectroscopic analysis and calculated and experimental electronic circular dichroism spectra. A plausible biosynthetic pathway for was proposed. Notably, compounds and exhibited significant inhibitory effects on tumor necrosis factor-α-induced nuclear factor-κB activity, with IC values of 0.95 and 5.57 μM, respectively.