Artemordins A-S, Cadinane-Type Sesquiterpenoid Dimers from Artemisia ordosica and Their Antihepatoma Activities

Nineteen new cadinane-involving sesquiterpenoid dimers, artemordins A-S (1-19), together with 13 known SDs (20-32) were isolated from Artemisia ordosica. Their structures and absolute configurations were established by comprehensive spectral analyses, X-ray single crystal diffraction, theoretical ECD, and NMR calculations. Chemically, artemordins A-F (1-6) were the first examples of two cadinane units constructed by unprecedented C-3-C-15 ' or C-3-C-13 ' single bond with an oxido-rearranged 6/5/6/6 fused ring system; artemordins G-K (7-11) were biogenetically connected by [4 + 2] cycloaddition reaction and artemordins G-J (7-10) possessed a novel 5/6/6/6/6/6/5-heptacyclic fused ring system. Artemordins L-S (12-19) were formed by esterification, which involved three different types of sesquiterpenoids. Antihepatoma assay suggested that the most active compounds, artemordins B and H (2 and 8), exhibited inhibitory activities on three hepatoma cell lines with IC50 values of 26.9 and 25.1 mu mol/L (HepG2), 29.5 and 18.3 mu mol/L (Huh7), 19.7 and 15.7 mu mol/L (SK-Hep-1).