Optimization of reaction conditions to fabricate nano-silver using Couroupita guianensis Aubl. (leaf & fruit) and its enhanced larvicidal effect

Abstract

Currently bioactive principles of plants and their nanoproducts have been extensively studied in agriculture and medicine. In this study Couroupita guianensis Aubl. leaf and fruit extracts were selected for rapid and cost-effective synthesis of silver nanoparticles (leaf-LAgNPs and fruit-FAgNPs). Various physiological conditions such as temperature, pH, concentration of metal ions, stoichiometric proportion of reaction mixture and reaction time showed influence on the size, dispersity and synthesis rate of AgNPs. Generation of AgNPs was initially confirmed with the surface plasmon vibrations at 420nm in UV–visible spectrophotometer. The results recorded from X-ray diffractometer (XRD) and Transmission electron microscope (TEM) supports the biosynthesis of cubic crystalline LAgNPs & FAgNPs with the size ranges between 10–45nm and 5–15nm respectively. Surface chemistry of synthesized AgNPs was studied with Fourier transform infrared spectroscopy (FTIR), it reveals that water soluble phenolic compounds present in the extracts act as reducing and stabilizing agent. Leaf, fruit extracts and synthesized AgNPs were evaluated against IV instar larvae of Aedes aegypti (Diptera; Culicidae). Furthermore, different extracts and synthesized AgNPs showed dose dependent larvicidal effect against A. aegypti after 24h of treatment. Compare to all extracts such as ethyl acetate (leaf; LC50 – 44.55ppm and LC90 – 318.39ppm & fruit; LC50 – 49.96ppm and LC90 – 568.84ppm respectively) and Methanol (leaf; LC50 – 85.75ppm and LC90 – 598.63ppm & fruit; LC50 – 67.78ppm and LC90 – 714.45ppm respectively) synthesized AgNPs showed extensive mortality rate (LAgNPs; LC50 – 2.1ppm and LC90 – 5.59ppm & FAgNPs; LC50 – 2.09ppm and LC90 – 5.7ppm). Hence, this study proves that C. guianensis is a potential bioresource for stable, reproducible nanoparticle synthesis (AgNPs) and also can be used as an efficient mosquito control agent.