Insights into biochemical, genotoxic, and molecular impacts, and molecular docking analysis-based possible mechanism of action of some essential oils against Culex pipiens larvae

Mosquitoes as vectors of life-threatening diseases pose significant risks to human health. While essential oils (EOs) are increasingly utilized as potential mosquitocides, their specific biochemical, genotoxic, and molecular impacts on mosquitoes are not well-documented. This study evaluates the biochemical, genotoxic, and molecular effects of five EOs on Culex pipiens larvae. Late third-instar larvae were treated for 24 h with LC₅₀ of orange, black pepper, camphor, lemon, and sandalwood EOs. Biochemical studies revealed that these EOs enhanced α-esterase, glutathione S-transferase, and peroxidase activities while reducing total protein, lipid, and carbohydrate contents and amylase, invertase, and trehalase activities. Acetylcholinesterase, protease, catalase, acid phosphatase, and alkaline phosphatase activities were EO-dependent. The comet assay revealed a slight increase in comet parameters, including tailed %, tail length, % DNA in the tail, tail moment, and olive tail moment, indicating low to mild DNA damage. Gene expression studies using orange and black pepper EOs demonstrated significant upregulation of genes related to immunity, detoxification, metabolism, and sensory perception. Molecular docking analysis revealed significant binding affinities between d-Limonene, the major component of orange oil, and its target proteins, with binding energies of −4.87, −6.33, −5.82, and − 3.38 kcal/mol for inhibitor of apoptosis protein, autophagy, juvenile hormone protein, and octopamine receptor, respectively. These findings highlight the potential of d-Limonene as an effective inhibitor, with favorable interactions at the receptor's active sites. This study provides insights into the possible mechanism of EO toxicity, offering promising directions for developing eco-friendly mosquito control strategies.