Cytotoxic Activity of Selected West Indian Medicinal Plants against a Human Leukaemia Cell Line

Objective: To assess the cytotoxic activities of crude extracts and solvent fractions of Spermacoce verticillata, Ficus pumila and Flemingia strobilifera against a MT-4 human leukaemia cancer cell line. Methods: Crude extracts of dried leaves of S verticillata, F pumila and F strobilifera were made by exhaustive methanol extraction, fractions were obtained from sequential extraction of the crude extract using solvents of increasing polarity. Dose responses corresponding to cell survival following 72-hour exposure to the extracts were determined using a leukaemia cancer cell line (MT-4). Cell viability was assessed using the MTT [3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide] assay reading absorbances at 570 nm. Comparisons were made with controls and cell survival, in each sample well, was determined based on the ratio of the absorbance of the sample to the control. Results: Crude extracts of S verticillata, F pumila and F strobilifera displayed cytotoxicity and the IC50 values were 89 mu g/ml, 131 mu g/ml and 81 mu g/ml, respectively. The petroleum ether and chloroform fractions of the crude extracts of S verticillata and F strobilifera showed potent cytotoxic activity but the highest cytotoxic activity was found in the chloroform and butanol fractions of F pumila with IC50 values of 23 mu g/ml and 26 mu g/ml, respectively Conclusion: The crude extracts of S verticillata, F pumila and F strobilifera were shown to be cytotoxic to the leukaemia cell line, MT-4 and IC50 values were determined. Fractionation of the crude extracts by solvent-solvent extraction enabled determination of the active fractions and their IC50 values. We propose that cytotoxic activity may be due to antioxidant compounds previously isolated from these plants.