Cytotoxic potential of ethanol extract of Parquetina nigrescens on MCF-7, C4-2WT, HT 29 and HTC 116 cell lines

The cytotoxic activity of ethanol extract of Parquetina nigrescen was investigated using a (3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, methylene blue and Trypan Blue exclusion assay on four human cancer cell lines, MCF-7, HT 29, HTC 116 and C4-2WT. A mitochondrial enzyme in living cells, succinate-dehydrogenase cleaves the tetrazolium ring and converts the MTT to an insoluble purple formazan whose intensity is directly proportional to the presence of viable cells in the microwell plate. Results showed a significant (p<0.05) cytotoxic effect of the extract in a dose dependent manner. Cytotoxicity increased with increase in the concentration of the extract used. GI50 results calculated after MTT test showed the concentration of ethanol extract of P. nigrescens required for 50% inhibition of the different cell lines as follows: MCF-7 = 2.61 µg/ml, C4-2WT = 8.33 µg/ml, HCT 29 = 3.47 µg/ml and HCT 116 =1.75 µg/ml. For the methylene blue assay, the number of viable cells present was significantly reduced (p<0.05) with an increase in the concentration of the extract and duration of exposure of the cells to the extract. The result of trypan blue assay showed a significant reduction (p<0.05) in the total count of viable cells and a significant increase (p<0.05) in the total count of non-viable cells over 72 h post-treatment with an extract of P. nigrescens. Comparatively, results obtained indicate that there is a correlation between the various methods adopted in establishing the antiproliferative and cytotoxic activity of ethanol extract of P. nigrescens obtained in this study. Key word: Parquetina nigrescens, cytotoxicity, human cell lines, MTT, trypan blue, methylene blue.