Medicinal plants are considered two-edged swords. They are pharmacologically beneficial and sometimes toxic when abused. The health benefit of medicinal plant is due to their abundant phytochemical endowment. The present study is aimed at evaluating the biosafety potentials of methanol extracts/fractions of Tapinanthus bangwensis (T. bangwensis) and Moringa oleifera (M. oleifera) leaves using Allium cepa (A. cepa) model. Cytotoxicity assay was carried out by A. epa model. The cytotoxicity parameters studied were number of dividing cells, percentage mitotic index (% MI), root tip growth length and chromosomal aberrations. The phytochemistry was determined by UV-spectrophotometry while 2,2-diphenyl-1-picrylhydrazine (DPPH) and nitric oxide (NO) were used to assay antioxidant activity. The A. cepa assay result showed that the inhibitory effect of M. oleifera on root tip growth length was higher compared to T. bangwensis at 60-100mg/100ml concentrations. Decreased number of dividing cells and percentage mitotic index as concentrations increased observed indicate cytotoxicity however the acetone fractions were most cytotoxic. The frequently occurring chromosomal aberrations observed were vagrant, bridged, attached and sticky chromosomes while C-mitosis and binuclear chromosomes were not observed. Therefore cytotoxic effect was significant at 100mg/100ml. The phytochemical screening of methanol extracts/fractions of T. bangwensis and M. oleifera leaves revealed the presence of alkaloids, flavonoids, phenolics, saponins and tannins however saponins were significantly abundant in both plants compared to others. Alkaloid content was found to be low but was not detected in the acetone fractions of the plants. Methanol extracts/fractions of the plants' leaves exhibited antioxidant activities but was more prominent in the ethylacetate fraction of T. bangwensis and acetone fraction of M. oleifera. In conclusion, administration at 100mg/100ml could be unsafe for the biological system.
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