Sublethal Effects of Selected Insecticides on Oxidative Status and Antioxidants in Cowpea Weevil, Callosobruchus Maculatus (F.) [Coleoptera: Chrysomelidae

Abstract

The toxicity of pesticides is correlated to the generation of free radicals, oxidative damage induction, increased lipid peroxidation (LPO) and interruption of the total antioxidant potential. The present study was undertaken to characterize the role of sublethal concentration (LC 50 ) of five selected insecticides (abamectin, emamectin benzoate, imidacloprid, indoxacarb and spinosad) on the oxidative stress and antioxidants in Callosobruchus maculatus (F.). The 24 h-LC 50 values of tested insecticides showed that emamectin benzoate was the most toxic insecticide (56.95 ppm) followed by indoxacarb (95.5 ppm) and spinosad (107.8 ppm) ; whereas abamectin and imidacloprid were the least toxic insecticides (148.2 and 209.8 ppm, respectively). For the oxidative status assays, the insect adults were exposed to cowpea seeds treated with LC 50 of each tested insecticide for 24 h. The results showed a significant increase in the lipid peroxidation (LPO), expressed as malondialdehyde (MDA) content, after exposure to emamectin benzoate and imidacloprid than that of the control. Data of the antioxidants showed that both glutathione reduced (GSH) and glutathione peroxidase (GPx), significantly elevated in all tested insecticide treatments in comparison with the control. However, the activity of superoxide dismutase (SOD) was significantly decreased particularly by abamectin, indoxacarb and spinosad. Our study revealed that oxidative imbalance induced in C. maculatus adults after exposure to sublethal concentration (LC 50 ) of the tested insecticides may be helpful for molecular base study of the toxicity mechanism of these insecticides. Also, such biomarkers used in the present study represent good indicators of pesticide-induced oxidative stress.