Antiproliferative Activity of Triterpenoid and Steroid Compounds from Ethyl Acetate Extract of Calotropis gigantea Root Bark against P388 Murine Leukemia Cell Lines

Calotropis gigantea has been known to produce bioactive secondary metabolites with antiproliferative activities against cancer cells. Herein, we extracted the secondary metabolites using ethyl acetate from its root bark and further tested its antiproliferative activities against P388 murine leukemia cell lines. The subfractions from the ethyl acetate extract was obtained from Vacuum Liquid Column Chromatography (VLCC), and followed by Gravity Column Chromatography (GCC). The subfraction C-2 and D-1 were identified to contain triterpenoids and steroids with the most potent cytotoxicity against Brine Shrimp Lethality Test (BSLT). A 3-(4,5-dimethylthiazol-2-yl) -2-5 diphenyl tetrazolium bromide (MTT) assay suggested that ethyl acetate extract has the highest antiproliferative activities against P388 murine leukemia cell lines (IC50 = 21.79 mu g/mL), as opposed to subfraction C-2 (IC50 = 50.64 mu g/mL) and subfraction D-1 (IC50 = 49.33 mu g/mL). The compound identified in subfraction C-2 and D-1 are taraxerol acetate and calotropone, respectively. Though taraxerol acetate and calotropone were active in inhibiting the leukemic cell lines, their IC(50)s were lower than the ethyl acetate extract, which is probably due to the synergism of the secondary metabolites.