Larvicidal potential of Trigonella foenum-graecum and Vitis vinifera seed oil nanoemulsions against Culex pipiens (Diptera: Culicidae)

Abstract

The increasing resistance of mosquito vectors to conventional insecticides highlights the urgent need for alternative and sustainable control strategies. Although plant-derived oils are selected due to their high content of bioactive compounds, especially unsaturated fatty acids and phenolic constituents, which have been reported to exhibit promising larvicidal activity and membrane-disrupting properties, their practical application is often limited by poor aqueous dispersibility, low physicochemical stability, and variable bioavailability. In addition, studies linking chemical composition to nano-enabled enhancement of larvicidal efficacy against Culex pipiens remain limited. Consequently, this study was established to develop nanoemulsions of Trigonella foenum-graecum (fenugreek seed oil) and Vitis vinifera seed oils (grape seed oils) and to evaluate their physicochemical characteristics and larvicidal activity. GC-MS analysis identified 14 and 34 compounds in fenugreek and grape seed oils, respectively, with fatty acids representing the dominant fraction. The prepared nanoemulsions exhibited nanoscale droplet sizes (194.8 nm for fenugreek and 55.21 nm for grape seed oil) and negative zeta potential values (-33.3 mV and - 29.9 mV), indicating good dispersion and colloidal stability. Transmission electron microscopy confirmed the formation of spherical and well-dispersed droplets. Larvicidal bioassays revealed a clear enhancement in toxicity for nanoemulsified formulations compared with crude oils. The fenugreek nanoemulsion showed the highest activity, with LC₅₀ values of 27.14 ppm and 23.20 ppm after 24 and 48 h of exposure, respectively. These findings indicate that nanoemulsification improves dispersion and enhances the biological performance of plant-derived oils. Overall, the results suggest that nanoemulsion-based formulations represent a promising approach for improving the efficacy of botanical larvicides. However, further studies are required to evaluate their performance under field conditions and to assess their environmental safety.