Alterations in the gut enzymes of Helicoverpa armigera (Hübner) induced by dietary Artemisia annua L. essential oil

The current study evaluated the impact of Artemisia annua L. essential oil (EO) on the alterations in the metabolic and detoxifying enzymes present in the gut of Helicoverpa armigera (Hübner) larvae. The A. annua EO was added to the larval diet in different concentrations ranging from 2.5 to 12.5%. The LD30 and LD50 values obtained were 3.78% and 5.16%, respectively. Dietary LD30 and LD50 concentrations of A. annua EO impacted all the metabolic and detoxifying enzymes adversely. The rise in the EO concentration in the diet affected the gut enzyme activity negatively. The dietary LD30 EO decreased the activity of α-amylase and proteases significantly by 64% and 68.3%, respectively which correspondingly rose to 74% and 72.9% with dietary EO at LD50 concentration. On the other hand, the lipase activity diminished at a proportionately lower rate; by 13% and 43.7% with respective dietary LD30 and LD50 EO. A significantly reduced level of detoxifying enzymes; glutathione-S-transferase, α-esterase and β-esterase was also recorded in the larvae fed on A. annua EO-added diet. Noticeably, the % decrease in α-esterase level was negatively correlated with the EO concentration in the diet unlike rest of the two enzymes. The impact of EO was also assessed on the total glucose levels which also reduced significantly in the larvae fed with dietary A. annua EO. Current results demonstrated the toxic effects of A. annua essential oil on the H. armigera larvae affecting their survival. Moreover, feeding the larvae with EO-containing diet inhibited the action of digestive and detoxifying enzymes indicating the persistent efficacy of EO. Future studies could identify the bioactive constituent responsible for these effects which can be used to formulate an eco-safe intervention against H. armigera.