Larvicidal and anti-bacterial efficacy of silver nanoparticles derived from Oxalis corniculata

Mosquito-transmitted diseases like malaria, zika, dengue, chikungunya, and filaria contribute to the emergence of discomfort and anxiety-inducing circumstances in tropical and subtropical countries. Plant-derived extract and silver nanoparticles were found to be potent larvicidal, eco-friendly, cost-effective, and least toxic to non-target organisms. In the current study, the green synthesis of the silver nanoparticles from Oxalis corniculata leaves was confirmed through the slow colour changes on mixing the aqueous extract with 1 mM silver nitrate (AgNO3) solution and further by UV–visible spectroscopy. The morphology and size of the synthesized AgNPs have been analysed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), x-ray diffraction (XRD), and zeta analysis. SEM and TEM analysis revealed that the shapes of AgNPs were hexagonal, spherical, and triangular, with an average size ranging from 15 to 50 nm. O. corniculata leaves extract mediated AgNPs found to be highly potent as larvicidal against larvae of Anopheles stephensi (LC50: 4.536 ppm, LC90: 22.097 ppm), Aedes aegypti (LC50: 7.255 ppm, LC90: 19.142 ppm), and Culex quinquefasciatus (LC50: 6.817 ppm, LC90: 22.660 ppm) after 72 h exposure. In different solvents, the chloroform-based extract has shown strong larvicidal activity. Hexane-based extract confirmed moderate toxicity, and ethanolic and methanolic extracts revealed less toxicity to the larvae of mosquitoes. O. corniculata-derived AgNPs showed strong antibacterial properties against the pathogenic bacteria Bacillus subtilis (gram-positive) and Escherichia coli (gram-negative), with the zone of inhibition 16 mm and 13 mm in diameter at 50 µg/ml concentration, respectively. AgNPs derived from the O. corniculata leaf extract were found to be harmless to Poecilia reticulata.