Induction of apoptosis by Ocimum sanctum (Holy basil) leaf extract against myeloid leukemia cells

Antineoplastic effect of Ocimum sanctum leaf extract was reported in our previous work. The cytotoxic potential of methanolic extract Ocimum sanctum (OSLE) was evaluated by MTT assay. Annexin-V FITC double staining was done to examine whether cell death occurred via apoptosis or necrosis. Gel electrophoresis, fluorescence microscopy, confocal microscopy and light microscopy were used to determine the cell morphology and fragmented DNA. JC-1 staining was also performed to measure the mitochondrial membrane potential. The phase distribution of the leukemia cell study was done by the cell cycle study. The pathway of apoptosis was studied by Caspase assay. OSLE significantly inhibited the cell viability in a time and concentration dependent manner in all the leukemia cells. After the treatment with OSLE, leukemia cells showed various signs of apoptosis like nuclear fragmentation, formation of apoptotic bodies, chromatin condensation and degraded DNA bands in cancer cells. The presence of apoptotic cells in the early and late stages was confirmed by the flow cytometric analysis. The cell cycle phase arrest was observed in the G0/G1 phase in the myeloid lymphoma and the multidrug resistant leukemia cells. A significant change in the mitochondrial membrane potential was observed in the OSLE treated leukemia cells with MMP shift assay. Caspase assay reveals that the pathway followed may be intrinsic apoptosis pathway. These finding suggest that the methanolic extract of Ocimum sanctum (OSLE) possesses anti-leukemic effects via apoptosis not necrosis along with insignificant toxicity.