Triterpenoids from Liquidambar Fructus induced cell apoptosis via a PI3K-AKT related signal pathway in SMMC7721 cancer cells

A previously undescribed taraxerene-type triterpenoid possessing a class of rare natural taraxerene triterpenoid possessing skeleton with 14, 28-lactone, two undescribed oleane-type triterpenoids, and twenty-five known triterpenoids were isolated from Liquidambar formosana (Hamamelidaceae). The structures of undescribed compounds were determined on the basis of 1D and 2D NMR spectroscopic, HR-ESI-MS, and X-ray crystallographic data analysis. Among the isolates, ursolic acid, 3,6-dion-20(29)-lupen-28-oic acid, and 3-oxo-12α-hydroxyoleanan-28,13β-olide induced a significant apoptosis in SMMC7721 cells in the flow cytometer experiment with apoptosis rates of 94.5%, 57.3% and 89.9% at 8.0 μM, respectively, exhibiting near equivalent apoptosis-inducing abilities to that positive drug taxol (apoptotic rate of 71.2% at 1.4 μM). Mechanism studies suggested that these three compounds could regulate the mitochondrial pathway by up-regulating the expressions of pro-apoptotic factors (Bad and Bax) and activating caspase-3 and caspase-9 to induce apoptosis. Further studies indicated that the pro-apoptotic effects of these three compounds were associated with PI3K-AKT pathway inhibition. Taken together, these studies provide evidence that triterpenoids from L. Fructus are promising candidates for the hepatocellular carcinoma therapy.