A battery of short-term in vitro assays for apoptosis and/or cell cycle arrest, cytotoxicity, genotoxicity and antigenotoxicity are used to screen and establish the efficacy of medicinal plants. This study evaluated three concentrations (0.1, 0.2 or 0.4 mg/ml) of methanolic leaf extracts of Artemisia afra and Leucosidea sericea and their individual mixtures with Ethyl methanesulfonate (EMS) (0.15 mg/ml) for induction of those end points using the in vivo Allium cepa assay. Cytotoxicity was measured by the mitotic index, genotoxicity was expressed as the number of aberrant mitotic cells per 100 mitotic cells and modulatory effect (ME) was calculated as: ME = (B - C) - (A - C) / (A - C) and the value, positive or negative, indicated the number of units of the mutagen-induced genotoxicity (A) that equaled the mixture-induced genotoxicity (B). The three concentrations of A. afra extract tested did not induce cell cycle arrest and were not cytotoxic. The 0.4 mg/ml concentration and its mixture with EMS were genotoxic. The concentrations of L. sericea extract tested did not induce cell cycle arrest, were not cytotoxic nor genotoxic to the A. cepa root tip cells. The mixture of either 0.2 or 0.4 mg/ml L. sericea extract with EMS was genotoxic. The mixture of 0.4 mg/ml L. sericea extract with EMS was significantly more (ME = 4.40>2) genotoxic than EMS alone. Leaf extracts of A. afra and L. sericea lacked cell-cycle arrest activity, were non-toxic but lacked antigenotoxic activity against EMS-induced genotoxicity. High concentrations of A. afra were genotoxic whereas high concentrations of L. sericea interacted synergistically with EMS. Chromosomal abnormalities observed included sticky chromosomes, c-mitosis, chromosome largards, chromosome fragments, anaphase and telophase bridges.
Key words: Anti-genotoxicity, cell cycle arrest, safety of medicinal plants of Lesotho.
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