New cytotoxic oleanane-type triterpenoids from the cones of Liquidamber styraciflua

Two new oleanane-type triterpenoids (1 and 2), together with two known compounds, 6beta-hydroxy-3-oxo-lup-20(29)-en-28-oic acid (3) and 3,11-dioxoolean-12-en-28-oic acid (4), were isolated from the stem bark of Liquidamber styraciflua. The structures of 1 and 2 were determined to be 25-acetoxy-3alpha-hydroxyolean-12-en-28-oic acid (1) and 3alpha,25-dihydroxyolean-12-en-28-oic acid (2) on the basis of spectroscopic methods and chemical conversion. Compound 1 showed strong cytotoxicity against a disease-oriented panel of 39 human cancer cell lines, although compounds 2, 3, and 4 showed weaker activity compared to 1.