Insights into the toxicity, biochemical activity, and molecular docking of Cymbopogon citratus essential oils and citral on Spodoptera littoralis (Lepidoptera: Noctuidae)

Insecticide resistance is a significant problem in insect management that can result from several processes including target-site change and increased activity of detoxifying enzymes. Spodoptera littoralis is one of the most resistant insect pests. For more effective insect management, alternatives to synthetic pesticides are encouraged. One of these alternatives is essential oils (EOs). Cymbopogon citratus EO and its main constituent citral were, therefore, considered in this study. The results revealed that C. citratus EO and citral exhibited significant larvicidal activity against S. littoralis, and the former was insignificantly more toxic than the latter. Additionally, treatments significantly affected the activity of detoxification enzymes. Cytochrome P-450 and glutathione-S-transferase were inhibited, while carboxylesterases, a-esterase and β-esterase, were induced. The molecular docking study indicated that citral bonded with the amino acids cysteine (CYS 345) and histidine (HIS 343) of cytochrome P-450. This result suggests that interaction with cytochrome P-450 enzyme is one key mechanism by which C. citratus EO and citral act in S. littoralis. The results of our study are hoped to contribute to a better understanding of the mechanism of action of essential oils at the biochemical and molecular levels and provide safer and more efficient pest management solutions for S. littoralis.