Larvicidal Efficacy of Plant-Mediated Silver Nanoparticles from Gmelina arborea and Hyptis suaveolens Against Wild Anopheles Vectors

Malaria remains a leading cause of morbidity and mortality in sub-Saharan Africa, with escalating insecticide resistance among Anopheles vectors threatening the sustainability of current control interventions. The search for novel, environmentally benign larvicidal agents has increasingly focused on nanotechnology innovations derived from medicinal plants. This study assessed the larvicidal potential of silver nanoparticles (AgNPs) synthesized using aqueous leaf extracts of Gmelina arborea and Hyptis suaveolens against wild Anopheles larvae collected from Lagos State, Nigeria. Fresh plant samples were authenticated botanically, and green synthesis of AgNPs was confirmed by a characteristic honey-brown colour change and UV–visible spectrophotometric analysis. Larvicidal bioassays were performed according to WHO guidelines using six graded concentrations under controlled insectary conditions. Mortality was recorded at 24, 48, and 72 hours, and toxicological responses were analyzed using probit regression in IBM SPSS v20. After 72 hours, both AgNP formulations demonstrated a concentration-dependent increase in larval mortality, with H. suaveolens AgNPs showing greater bioefficacy than G. arborea AgNPs. Specifically, H. suaveolens AgNPs achieved LC₅₀ and LC₉₅ values of 0.292 ppm and 1.948 ppm respectively, whereas LC₅₀ = 0.469 ppm and LC₉₅ = 3.919 ppm were recorded for G. arborea AgNPs. Control mortality remained ≤10%, validating experimental reliability. The potent larvicidal activity displayed by both plant-derived AgNPs suggests that phytochemical-mediated nanoparticle synthesis may enhance toxicity against mosquito vectors while retaining environmental safety. These findings provide evidence supporting the integration of green nanotechnology into vector-control strategies to help mitigate resistance to conventional insecticides and strengthen malaria prevention efforts in endemic communities.