Cytotoxic cycloartane-type triterpenes from Combretum quadrangulare.

Seven novel cycloartane-type triterpenes were isolated from Combretum quadrangulare, and their structures were elucidated on the basis of spectral analysis. All these compounds were tested for their cytotoxicity against murine colon 26-L5 carcinoma cells. Methyl quadrangularate B (2) and methyl quadrangularate D (4) exhibited potent cytotoxicity having ED50 values 9.54 and 5.42 microM, respectively.