Comparative larvicidal efficacy and phytochemical profiling of selected Solanaceous hexane extracts against Culex pipiens and Aedes aegypti

Mosquito-borne diseases pose a major global health burden, and the effectiveness of conventional insecticides is increasingly limited by resistance and environmental concerns. This study provides a comparative assessment of the larvicidal activity and phytochemical composition of n-hexane extracts from four Solanaceous plants: Capsicum annuum (Cap.), Datura stramonium (Dat.), Nicotiana tabacum (To.), and Withania somnifera (Wt.). Volatile constituents were characterized using GC-MS analysis, and larvicidal activity was evaluated against Culex pipiens and Aedes aegypti, with LC₅₀ and LC₉₀ values determined at 24 and 48 h. post-treatment. All extracts showed concentration- and time-dependent toxicity, achieving near-complete mortality at 1000 ppm for N. tabacum and D. stramonium. Nicotiana tabacum showed the highest efficacy against Cx. pipiens (LC₅₀ = 120.45 and 95.30 ppm, at 24 and 48 h), whereas Ae. aegypti showed comparatively lower susceptibility. Biochemical analyses revealed significant inhibition of acetylcholinesterase (AChE), α- and β-esterases, and GABA-transaminase, alongside an imbalance in antioxidant defenses, suggesting a multi-system physiological impact. GC-MS profiling identified distinct phytochemical compositions, particularly the alkaloid and fatty acid content identified in the more potent extracts. The four extracts contained a vast array of phytochemical components, reaching 110 components belonging to capsaicinoids and hydrocarbons for Cap; To. and Dat. were rich in fatty acids, particularly n-hexadecanoic and oleic acids; and Wt. exhibited a hydrocarbon-rich profile with cyclic and branched alkanes. Oleic acid was the only compound shared among three samples (Cap., To., and Dat.), whereas no compound was common across all samples. This study provides the first comparative assessment of four Solanaceous genera using integrated phytochemical, biochemical, and larvicidal analyses. The findings identify N. tabacum as the most promising candidate and establish a foundation for bioassay-guided development of plant-based bio-insecticides. This integrative approach offers a practical framework for screening botanical extracts for vector control programs, though further studies are needed to confirm the causal phytochemicals and mechanisms.