Insecticidal and Oxidative Effects of Azadirachtin on the Model Organism Galleria Mellonella L. (Lepidoptera: Pyralidae)

Abstract

The insecticidal effects, specifically, changes in hemolymph total protein and malondialdehyde (MDA) levels, and antioxidant enzyme activities of azadirachtin (AZA) given to the wax moth, Galleria mellonella L. (Lepidoptera: Pyralidae) larvae via force feeding were investigated. Bioassays showed that the LD50 and LD99 (lethal dose) values of AZA were 2.1 and 4.6 mu g/larva, respectively. Experimental analyses were performed with five doses of AZA (0.5, 1, 1.5, 2, and 3 mu g/larva). Total protein level in larval hemolymph increased at all AZA doses at 24 h whereas a considerable decrease was observed at 2 and 3 mu g/larva doses, and only an increase displayed at 1.5 mu g/larva at 72 h. The level of MDA increased at 2 and 3 mu g/larva doses at 24 h compared with controls. This trend was also observed at 1.5, 2, and 3 mu g/larva doses at 72 h and MDA levels were lower when compared with those of 24 h at all doses except for 1.5 mu g/larva dose. Catalase activity decreased at 1, 1.5, and 2 mu g/larva doses at 24 h whereas increased at all doses except for 0.5 mu g/larva at 72 h compared with controls. AZA led to a decline in superoxide dismutase activity at all experimental doses at 24 and 72 h except for 3 mu g/larva doses at 72 h. An increase in glutathione-S-transferase (GST) activity was evident at all AZA doses at 24 h. AZA displayed 68% decline in GST activity at 72 h post treatments when compared to 24 h. Consequently, We infer that the toxicity of AZA extends beyond its known actions in molting processes to redox homeostasis