Larvicidal activity of green synthesized silver nanoparticles using Excoecaria agallocha L. (Euphorbiaceae) leaf extract against Aedes aegypti.

Green synthesis of silver nanoparticles (AgNPs) using plant extracts has been achieved by eco-friendly reducing and capping agents. The present study was conducted to evaluate the larvicidal efficacies of AgNPs synthesized using aqueous leaf extracts of Excoecaria agallocha against dengue vector, Aedes aegypti. The 3rd and 4th instar larvae of A. aegypti were exposed to various concentrations of aqueous extracts of E. agallocha, synthesized AgNPs and also crude solvent extracts (methanol and chloroform) for 24 h. The formation of AgNPs using aqueous leaf extracts was observed after 30 min with a characteristic colour change. The results recorded from UV-Vis spectrum, XRD, FTIR, EDX, SEM and HR-TEM were used to characterize and confirm the biosynthesis of AgNPs. The highest larvicidal efficacy of synthesized AgNPs was observed against 3rd instar larvae at LC50 4.65 mg/L, LC90 14.17 mg/L and 4th instar larvae with a concentration of LC50 6.10 mg/L, LC90 15.64 mg/L. A significant larvicidal activity was also observed with crude methanolic extracts against 3rd instar larvae at a concentration LC50 41.74 mg/L, LC90 123.61 mg/L and 4th instar larvae at a concentration of LC50 52.06 mg/L, LC90 166.40 mg/L as compared to the chloroform extract.