Structural characterization and antioxidative activity of lancifonins: unique nortriterpenoids from Schisandra lancifolia.

Six unique nortriterpenoids, lancifonins A-F (1-6), were isolated from Schisandra lancifolia. Their absolute configurations were determined by X-ray diffraction and ECD calculation. The conformational analysis of 1 was performed due to the unanticipated changes of Cotton effects in its ECD spectrum. Compounds 5 and 6 possess a unique 7/7 fused carbocyclic core with an internal ester bridge between C-9 and C-14, and 5 exhibited protective activity against H2O2-induced oxidative damage on Caco-2 cells.