Biological Synthesis of Silver Nanoparticles from Anisomeles Indica and their Mosquito Efficacy

Mosquitoes transmit serious human diseases, causing millions of deaths every year. The use of synthetic insecticides to control vector mosquitoes has caused physiological resistance and adverse environmental effects in addition to high operational cost. The use of synthetic mosquitocides often leads to high operational costs and adverse non-target effects. Recently, plant borne compounds have been proposed for rapid extracellular biosynthesis of mosquitocidal nanoparticles. However, the impact of these nano mosquitocides against biological control agents of mosquito larval populations has been poorly studied. The present study was carried out to establish the larvicidal potential of leaf extracts of Anisomeles indica and synthesized silver nanoparticles using aqueous leaf extract against late third instar larvae of Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus. Larvae were exposed to varying concentrations of plant extracts and synthesized AgNPs for 24 hours. The results were recorded from UV–visible spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and energydispersive X-ray spectroscopy analysis support the biosynthesis and characterization of AgNPs. The maximum efficacy was observed in synthesized AgNPs against the larvae of An. stephensi (lethal concentration (LC50)=25.67 μg/mL; LC90 50.09 μg/ mL), Ae.aegypti (LC50=27.40 μg/mL; LC90 53.05 μg/mL), and Cx. quinquefasciatus (LC50=29.67 μg/mL; LC90 57.28 μg/mL), respectively. No mortality was observed in the control. This is the first report on mosquito larvicidal activity of plant-synthesized nanoparticles. Thus, the use of A.indica to synthesize silver nanoparticles is a rapid, ecofriendly, and a single-step approach and the Ag NPs formed can be potential mosquito larvicidal agents.