Botanical extracts and essential oils derived from medicinal plants have attracted increasing interest as eco-friendly alternatives to synthetic insecticides for mosquito control. In the present study, nanoemulsion formulations of Araucaria heterophylla and Azadirachta indica leaf extracts were developed to enhance their insecticidal efficacy against Culex pipiens and their biochemical impacts. Nanoemulsions were characterized using UV–Vis spectroscopy, dynamic light scattering, zeta potential analysis, and transmission electron microscopy, confirming stable nanoscale droplets with spherical morphology. Biochemical analyses revealed significant inhibition of detoxification (acetylcholinesterase, α- and β-esterases), metabolic (GABA-T, amylase, lipase), and antioxidant enzymes (SOD, GST, CAT, GSH). Elevated lipid peroxidation and protein carbonyl levels reflected severe oxidative stress, with A. indica nanoemulsion inducing the most potent effects. The phytochemical profiling of the two plants leads to the identification of 28 and 42 volatile components from the AIW and AH n-hexane extracts, respectively. The identified components belonged to the alkyl benzene and hydrocarbons in common between the two plants. However, AH-Hex was rich with sesquiterpenoids and oxygenated terpenoids such as caryophyllene, humulene, β-bisabolene, carotol, and kaurene derivatives, while AIW-Hex showed methyl esters of palmitic and stearic acids, along with long-chain branched alkanes and alcohols, as its main components. In addition, the UPLC/MS-assisted profiling of Me, Eth. Ac., and Aq. extracts revealed a vast array of metabolites, counted as 56 and 55 for AIW and AH extracts, respectively. The AH extracts were presented with a rich diterpenoid profile together with several flavonoids, fatty acids, and phenolic acids, while the AIW extracts were particularly rich with flavonoids, followed by limonoids, cinnamic acid derivatives, and fatty acids. Overall, this study demonstrates that nanoemulsions of A. indica and A. heterophylla leaves significantly enhance larvicidal efficacy against Cx. pipiens through biochemical disruption and oxidative stress induction.
Alkeridis et al. (Wed,) studied this question.