Eco-friendly bioactives from Nyctanthes arbor-tristis (L.) for targeted control of Aedes aegypti and Culex quinquefasciatus with reduced impact on Toxorhynchites splendens

With rising resistance to synthetic insecticides, eco-friendly alternatives for mosquito control are urgently needed. This study evaluates the toxicological effects of [3-(Imidazol-1-yl) propyl] (thiophen-2-ylmethyl)amine and chrysanthemic acid, key constituents of essential oil derived from Nyctanthes arbor-tristis exhibit larvicidal activity against Aedes aegypti and Culex quinquefasciatus larvae. Gas chromatography-mass spectrometry analysis identified 39 bioactive constituents with [3-(Imidazol-1-yl) propyl] (thiophen-2-ylmethyl)amine and chrysanthemic acid showing potent larvicidal activity at 2.5 mg/L, resulting in over 75% mortality in second to fourth instar larvae. The essential oil at 250 mg/L demonstrated even higher efficacy, causing 96.5% and 97.5% mortality in second instar Ae. aegypti and Cx. quinquefasciatus, sequentially. Enzyme inhibition assays demonstrated reduced activity of α- and β-carboxylesterase and elevated levels of detoxification enzymes, glutathione S-transferase and cytochrome P450, suggesting marked disruption of larval midgut enzymatic function. Repellent testing showed dose-dependent efficacy, with 250 mg/L essential oil achieving 75.13% repellency against Ae. aegypti and 71.1% against Cx. quinquefasciatus after 210 min. Histological examination confirmed severe midgut tissue damage in treated larvae, highlighting the targeted action of the essential oil and its metabolites. Minimal toxicity was observed in the non-target predator Toxorhynchites splendens, suggesting the potential of N. arbor-tristis essential oil and its derivatives as sustainable and environmentally responsible alternatives for mosquito control.