PHYTOFABRICATION OF SILVER NANOPARTICLES USING THE MANGROVE ASSOCIATE, HIBISCUS TILIACEUS PLANT AND ITS BIOLOGICAL ACTIVITY AGAINST CERTAIN INSECT AND MICROBIAL PESTS

Plants have a rich source of phytochemicals which can produce very stable and active nanoparticles. We report an economic and ecofriendly phytofabrication of nanoparticles using mangrove associate Hibiscus tiliaceus leaf extract for the first time. The synthesized NPs were characterized using different analytical methods. Further these bioinspired sliver nanoparticles (AgNP) were evaluated for insecticidal activities against two major agricultural pests, Tobacco cutworm, Spodoptera litura F., the cotton bollworm, Helicoverpa armigera H., three major stored product pests, flour beetle, Tribolium castaneum H., lesser grain borer, Rhyzopertha dominica F. and rice weevil, Sitophilus oryzae L. and also antibacterial activity against phytopathogens Xanthomonas campestris var campestris and Ralstonia solanacearum (Smith). For understanding the differences between the biological activity of biosynthesized and chemically synthesized nanoparticles comparisons between the toxicities and antifeedant activities were made. Transmission Electron Microscopic (TEM) studies showed spherical shaped nanoparticles in a size range of 20-65 nm (average mean size 40), while X-ray diffraction pattern revealed face centered cubic (fcc) structure when H. tiliaceus leaf was used for bioreduction. Fourier Transform Infrared Spectroscopy (FT-IR) was carried out to identify the proteins that bound specifically on the Ag surface, which increased the stability of the particles. H. tiliaceus mediated AgNPs showed excellent antifeedant activity against S. litura, H. armigera, but were less toxic to all the stored product pests tested, but comparatively higher than the chemically synthesized AgNPs. The green AgNPs exhibited potent antibacterial activity with varying degrees against X. campestris and R. solanacearum as evidenced by their zone of inhibition at all concentrations.