Moringa oleifera, from the family Moringaceae, is used as a source of vegetable and herbal medicine and in the treatment of various cancers in many African countries, including Kenya. The present study involved the phytochemical analyses of the crude extracts of M.oleifera and biological activities (antioxidant, cytotoxicity and induction of apoptosis in-vitro) of selected isolated compounds. The compounds isolated from the leaves and seeds of the plant were quercetin-3-O-glucoside (1), 4-(β-D-glucopyranosyl-1→4-α-L-rhamnopyranosyloxy)-benzyl isothiocyanate (2), lutein (3), and sitosterol (4). Antioxidant activity of compound 1 was significant when compared to that of the control, while compound 2 showed moderate activity. The cytotoxicity of compounds 1 and 2 were tested in three cell lines, viz. liver hepatocellular carcinoma (HepG2), colon carcinoma (Caco-2) and a non-cancer cell line Human Embryonic Kidney (HEK293), using the MTT cell viability assay and compared against a standard anticancer drug, 5-fluorouracil. Apoptosis studies were carried out using the acridine orange/ethidium bromide dual staining method. The isolated compounds showed selective in vitro cytotoxic and apoptotic activity against human cancer and non-cancer cell lines, respectively. Compound 1 showed significant cytotoxicity against the Caco-2 cell line with an IC50 of 79 μg mL(-1) and moderate cytotoxicity against the HepG2 cell line with an IC50 of 150 μg mL(-1), while compound 2 showed significant cytotoxicity against the Caco- 2 and HepG2 cell lines with an IC50 of 45 μg mL(-1) and 60 μg mL(-1), respectively. Comparatively both compounds showed much lower cytotoxicity against the HEK293 cell line with IC50 values of 186 μg mL(-1) and 224 μg mL(-1), respectively.