Antioxidant and detoxifying enzymes response of stored product insect pests to bioactive fractions of botanical extracts used as stored grains protectant

Abstract

Recurrent exposure of stored product insects to synthetic insecticides resulted in the development of resistance which occurs due to changes in insect metabolic enzymes. The inhibitory effect of ethyl acetate active fraction of Mitracarpus villosus, Bridelia micrantha, and Clerodendrum capitatum on antioxidant and detoxifying enzymes of stored product insects was investigated in this study. Sitophilus oryazae, Tribolium castaneum, and Rhizopertha dominica were exposed to 5 and 20 μl concentrations of ethyl acetate active fraction VI 50:50 derived from glass column chromatography in a fumigation chamber and were homogenized separately. The results showed that SOD, CAT, GPx, GSH, and GST activities were dosage-time-dependent. Adult insects exposed to different dosages of C. capitatum active fractions significantly inhibited GST and GPx activities, and SOD, CAT, and GSH activities were induced in comparison to insects in control. While, M. villosus and B. micrantha extracts exhibited a significant increase (p < 0.05) in SOD, CAT, and GSH in contrast to the inhibitory effects on GST and GPx. These results clearly show that stored beetles differ in their response to different enzymatic activities and that the evaluated plant materials may be used as an eco-friendly biopesticide in the IPM strategy for safeguarding stored food grains against stored produced insect pests.