CYTOTOXIC AND APOPTOGENIC EFFECTS OF A BIOACTIVE FRACTION ISOLATED FROM THE LEAVES OF A TRADITIONAL MEDICINAL PLANT TRIDAX PROCUMBENS

Objective: To investigate the anti-proliferative effects of T. procumbens leaf extracts on the growth of MCF 7, Hep G2 and K562 cells. An attempt was made to partially purify the cytotoxic acetone extract using a bioassay-guided isolation procedure and the apoptosis-inducing activity of bioactive sub-fraction, F15 (fraction 15), was probed further against K562 cells. Methods: Cytotoxicity of extracts was evaluated by MTT assay. Hoechst 33258, acridine orange/ethidium bromide and AnnexinV- FITC staining was performed to detect apoptosis. Mitochondrial membrane potential and cell cycle distribution were measured by flow cytometry. DNA fragmentation, alkaline comet assays and Western blotting of key apoptosis-related proteins were also performed. Results: The F15 showed the highest antiproliferative activity against K562 cells leaving the normal peripheral blood lymphocyte unaffected. TLC of F15 displayed a total number of four bands that individually exhibited lower anticancer activities than that of F15, suggesting the possibility of synergism among them. F15 induced phosphatidylserine externalization, loss of mitochondrial membrane depolarization, DNA laddering, increased sub-G1 population and altered expression of caspase 3, -9 and PARP. Conclusion: Taken together, our results indicate that F15 triggers inhibition of tumor cell growth by inducing intrinsic apoptotic pathway in K562 cells.