Evaluation of Silver Nanoparticle Toxicity of Coleus aromaticus Leaf Extracts and its Larvicidal Toxicity against Dengue and Filariasis Vectors

Abstract

Mosquitoes in the larval stage are attractive targets for pesticides as mosquitoes breed in water, and thus, it is easy to deal with them in this habitat. The use of conventional pesticides, in the water sources, introduces many risks to people and environment. Natural pesticides, especially those derived from plants, are more promising in this aspect. Plants are rich in secondary metabolites which are an efficient source for natural pesticide. Nanoparticle-conjugated plant extracts increase the botanical of plant extracts and are hence attractive sources for mosquito control. The present study investigates the plant-mediated synthesis of silver nanoparticles using the Coleus aromaticus leaf extracts against dengue and filariasis mosquito vectors. Silver nanoparticle-conjugated plant extracts were characterized by Ultraviolet-Visible spectroscopy, scanning electron microscopy, Energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy. The size of the silver nanoparticles was 262.7 nm. The larvicidal potential of solvent leaf extracts of Coleus aromaticus and synthesized silver nanoparticles using aqueous leaf extract against fourth instar larvae of Aedes aegypti and Culex quinquefasciatus was assessed. Larvae were exposed to varying concentrations of plant extracts and synthesized AgNPs plant extracts post 24 h; mosquito larvae showed maximum mortality in leaf extracts synthesized AgNPs against the fourth instars larvae of Ae. aegypti and Cx. quinquefasciatus. These results suggest that the synthesized AgNPs from leaf extracts have a higher larvicidal potential as compared to crude solvent extracts thus making them an effective combination for controlling dengue and filariasis vectors.