Peppermint (Mentha piperita) extract modulates the genotoxic effects of Cypermethrin and Malathion insecticides on Allium cepa root cells

Abstract The potential protective effect of peppermint (Mentha piperita; Labiatae) water extract was investigated on onion (Allium cepa) root tips that were exposed to cytotoxic and genotoxic insecticides; cypermethrin or malathion. Cypermethrin was tested at 0.019, 0.038 and 0.075mg/ml and malathion at 0.235, 0.469 and 0.938mg/ml, based on concentrations used in the field. Parallel doses of 4µg/ml or 8µg/ml peppermint extract were applied for each insecticide treatment, while distilled water was used as a control. Exposure time was 8 hours for all treatments. Mitotic index (MI), cell proliferation kinetics (CPK), percentage of mitotic aberrations (MAs) and nuclear aberrations (NAs) were evaluated. Both insecticides exerted a significant decline in MI (p < 0.001) and mitotic kinetics aberrations, which indicated potent cytotoxicity of both insecticides even at lower doses, where significant reduction of MI (more than 50% below the control) because of prophase imbalance and metaphase arrest. Both insecticides induced a concentration dependent MAs ranging between 19.0 and 29.6%. MAs and TAs of cypermethrin were significant at the high dose, while those caused by malathion were significant at both medium and high doses. Aberrations observed included bridges, vagrants, laggards, stickiness, multipolar, binucleated cells, micro-, lobed, blebbed and vacuolated nuclei. Application of peppermint water extract to both insecticides reduced the cytotoxic and genotoxic capacity of these insecticides.