Epimeric spirolactone-type triterpenoids from Abies faxoniana Rehd

Phytochemical investigation of Abies faxoniana Rehd. led to the isolation of two pairs of new epimeric spirolactone-type triterpenoids (1/1′ and 2/2′) and 11 known terpenoids (3 − 13). Compounds 1/1′ and 2/2′ were isolated as epimeric mixtures due to the C-23 ketal tautomerism in their spirolactone structures. The dynamic HPLC manifested that the C-23 epimeric mixtures interconverted into each other in solution. Structure determinations were based on extensive NMR and HRESIMS spectroscopic analysis. Meanwhile, their cytotoxic activities were tested by MTT method. Compound 5 showed cytotoxicities against MCF-7 and A549 cells with IC50 values of 6.5 and 5.7 μM, respectively. Compounds 1/1′ had IC50 values of 10.0 and 12.3 μM for Huh7 and SMMC7721 cells, respectively.

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