Cytotoxic Triterpenoids from the Stalks of Microtropis triflora

Bioassay-guided phytochemical investigation of the stalks of Microtropis triflora Merr. & F.L. Freeman led to the isolation of ten triterpenes 1 - 10, including one novel compound 3,24-epoxy-2α,24-dihydroxyfriedelan-29-oic acid (1). Their chemical structures were identified on the basis of spectroscopic analysis, including HR-ESI mass spectrometry, 1D- and 2D-NMR (¹ H, ¹³ C, ¹ H,¹ H-COSY, HSQC, HMBC, and NOESY), and by comparison with the data reported. The cytotoxicities of compounds 1 - 10 against a panel of cultured human tumor cell lines (Bcap37, SMMC7721, HeLa, CNE) were evaluated. The new compound 1 showed moderate anti-tumor activities with IC₅₀ values of 39.22, 29.24, 23.28, and 68.81 μm/ml, respectively. These results might be helpful for explaining the use of M. triflora in traditional medicine. Triterpenes are characteristic of Microtropis genus and could be useful as potential chemotaxonomic markers.