Isolation, structure elucidation, and induction of hepatoma cell apoptosis of abietane diterpenoids from Abies faxoniana.

Two new abietane diterpenoids (1-2) and 13 known compounds (3-15) were characterized from the branches and leaves of Abies faxoniana. The chemical structures of the new diterpenoids (1-2) were determined through the analysis of various 1D/2D NMR techniques. Compound 3 is 151,617-trinor-abietane diterpenoid conjugated with a three-membered epoxide ring. The isolated diterpenoids were tested for their cytotoxicities. Among them, compound 3 exhibited the strongest antiproliferative effect against human hepatoma cell SMMC7721 with an IC50 value of 12.5 μM. To elucidate the preliminary mechanism responsible for compound 3-induced inhibition of cell proliferation, we investigated the effects of compound 3 on apoptosis, cell cycle progression, and reactive oxygen species generation in SMMC7721 cells. The results showed that compound 3 induced cell apoptosis and excessive ROS production, but did not change the cell cycle distribution in SMMC7721 cells.