Isolation, structure elucidation, and induction of hepatoma cell apoptosis of abietane diterpenoids from <i>Abies faxoniana</i>

<p>Two new abietane diterpenoids (<b>1</b>–<b>2</b>) and 13 known compounds (<b>3</b>–<b>15</b>) were characterized from the branches and leaves of <i>Abies faxoniana</i>. The chemical structures of the new diterpenoids (<b>1</b>–<b>2</b>) were determined through the analysis of various 1D/2D NMR techniques. Compound <b>3</b> is 151,617-trinor-abietane diterpenoid conjugated with a three-membered epoxide ring. The isolated diterpenoids were tested for their cytotoxicities. Among them, compound <b>3</b> exhibited the strongest antiproliferative effect against human hepatoma cell SMMC7721 with an IC<sub>50</sub> value of 12.5 μM. To elucidate the preliminary mechanism responsible for compound <b>3</b>-induced inhibition of cell proliferation, we investigated the effects of compound <b>3</b> on apoptosis, cell cycle progression, and reactive oxygen species generation in SMMC7721 cells. The results showed that compound <b>3</b> induced cell apoptosis and excessive ROS production, but did not change the cell cycle distribution in SMMC7721 cells.</p>