Phytochemical composition and cytotoxicity of ethanolic extracts of some selected plants

This study determines the phytochemical contents of selected medicinal plant extracts quantitatively using spectrophotometry and to evaluate their safety on mammalian cells in vitro using tetrazolium-based colorimetric cytotoxicity assay. Twenty-two ethanolic plant extracts were assessed, and the result showed that Psidium guajava had the highest concentration of alkaloids (219.06 +/- 11.50mg/g dry-weight (dw)). In contrast, Acacia nilotica leaf extract with 191.60 +/- 9.07mg/gdw had the highest level of flavonoids. Vernonia amygdalina and Moringa oleifera contained more steroids than the other plant extracts while condensed tannin was highest in Carya illinoinensis (21.72 +/- 0.84 mg/g dw). Coffea arabica, Acacia nilotica leaf, Vernonia amygdalina, Carya illinoinensis and Psidium guajava had more saponins than the other plant extracts. Regarding cytotoxicity evaluation, Allium cepa and Tulbaghia violacea with concentration killing 50% of cells (LC50) values of 0.5182 +/- 0.40 and 0.4909 +/- 0.034 mg/ml, respectively, were the safest of all the plant extracts. Acacia nilotica pod and Camelia japonica leaf extracts were the most cytotoxic with LC50 values of 0.0101 +/- 0.016 and 0.0151 +/- 0.005 mg/ml, respectively, which are well below the recommended toxic cut-off point (0.03mg/ml). The best selectivity index (SI) value of 1.061 was obtained with Aloe ferox against S. aureus, which is a Gram-positive bacterium.