Two new tirucallane triterpenoids from the leaves of Aquilaria sinensis.

Two new tirucallane triterpenoids, aquilacallanes A-B (1-2), together with 15 known compounds (3-17) were isolated from the leaves of Aquilaria sinensis. The structures of these new compounds were elucidated on the basis of extensive spectroscopic analyses. All compounds were evaluated for their cytotoxic activity against five human cancer cell lines. The known compounds, ursolic acid (7) and 5,7,4'-trimethoxyflavone (14), exhibited weak cytotoxic activity against some cells.