The triterpenes, squalene (1), friedelin (2) and a mixture of ursolic acid (3a) and oleanolic acid (3b) in a 2:3 ratio, and a mixture of β-sitosterol (4a) and stigmasterol (4b) in a 2:1 ratio, obtained from the dichloromethane extract of Pipturus arborescens (Link) C.B. Rob., were evaluated for their anti-proliferative activities against three human cancer cell lines, breast (MCF-7) and colon (HT-29 and HCT-116), and a normal cell line, human dermal fibroblast- neonatal (HDFn) using the in vitro PrestoBlue® cell viability assay. The HCT-116 cell line was most susceptible to the compounds and mixtures tested. Triterpene 1 was most cytotoxic against HCT-116 and MCF-7 with IC50 values of 4.21 and 5.92 μg/mL, respectively. Triterpene 2 and the mixture of 3a and 3b were highly anti-proliferative against HCT-116 cells (IC50 of 1.22 and 1.66 μg/mL, respectively) and moderately inhibitory against MCF-7 cells (IC50 of 16.51 and 23.97 μg/mL, respectively). The mixture of 4a and 4b exhibited high cytotoxicity against HCT-116 cells (IC50 of 1.14 μg/mL). Compounds 1-4b showed the least activity against HT-29 cells (IC50 of 11.97 to 52.52 μg/mL). Cytotoxic effect was not observed against HDFn cells (>100 μg/mL). Comparing the effects of 1-4b on the two colon cancer cell lines, the IC50 values of 1-4b against HCT-116 were lower than those of HT-29.
Key words: Pipturus arborescens (Link) C.B. Rob., squalene, friedelin, ursolic acid, oleanolic acid, β-sitosterol, stigmasterol, cytotoxicity, MCF-7, HCT-116, HT-29, HDFn