Bioactive Sesquiterpene Lactones Isolated from the Whole Plants of Vernonia cinerea.

Twelve sesquiterpene lactones were isolated from the whole plants of Vernonia cinerea. These included eight new compounds, vercinolides A-H (1-8), along with four known substances (9-12). The structures of the new compounds were determined by 1D and 2D NMR experiments and mass spectrometric methods. The absolute configurations of compounds 1-8 were determined by Mosher experiments and ECD data. Compounds 1-8 are the first examples of a new class of sesquiterpene lactones possessing a rare 4α,10α-ether ring and a 2,14-ether ring. Compounds 1-4, 6, 8, 10, and 12 were evaluated for their cytotoxic and anti-inflammatory activities. Compounds 10 and 12 exhibited inhibitory effects against nitric oxide production in lipopolysaccharide-activated RAW 264.7 mouse macrophage cells with IC₅₀ values of 21 and 23 μM, respectively. Both compounds were inactive for HeLa cells (IC₅₀ > 10 μM).