Abstract
We isolated 8 novel 28-noroleanane-derived spirocyclic triterpenoids with unusual skeleton structures, phlomisone (1), phlomistetraol A (2), phlomistetraol B (3), phlomistetraol C (4), phlomispentaol (5), phlomishexaol A (6), phlomishexaol B (7), and phlomisin (8), from the ethanol extract of Phlomis umbrosa rhizomes. Their structures were elucidated on the basis of spectroscopic methods, including 1D, 2D nuclear magnetic resonance (NMR), high-resolution mass spectrometry (HR-MS), and X-ray analyses. Compounds 1—3, 5, and 7 exhibited positive cytotoxic activities against the carcinoma cell lines Hela and L929 in vitro, and these bioactive data suggested that the C-18 and C-21 positions had oxygenated functions that can improve the activity of the compound.
