Green synthesis of silver nanoparticles with Torenia fournieri leaf extracts and assessing the antioxidant and antibacterial properties, para-nitrophenol catalysis, and nanotoxicity

Abstract

Nanotechnology provides new opportunities in medicine and environmental remediation through the development of metal-based nanoparticles. This study focused on the green synthesis of silver nanoparticles (AgNPs) using five varieties of Torenia fournieri; Deep blue, Blue White, Rose, Burgundy, and Lemondrop. The purpose was to evaluate the potential of plant-based AgNPs in catalytic, antimicrobial, antioxidant, and cytotoxic applications. The optimal conditions for AgNP synthesis were 90 °C for 60 minutes. Scanning Electron Microscopy revealed spherical 25–60 nm Lemondrop_AgNPs. Antioxidant profiling indicated that AgNPs had higher Total Phenolic Content, Total Flavonoid Content, and Total Antioxidant Capacity compared to water extracts (WEs). Para-Nitrophenol catalysis was observed at 4000 ppm AgNPs within 45 minutes, with Deepblue_AgNPs showing the highest rate constant (k = 0.0211 min⁻¹). All AgNPs showed higher antibacterial activity against Staphylococcus aureus and Escherichia coli compared to WEs, with Escherichia coli showing higher zones of inhibition. Cytotoxicity of AgNPs using Artemia salina was assessed, and 100% viability was recorded at 200 ppm and 800 ppm of AgNPs. In silico docking studies revealed that the 3-atom Ag cluster showed lower binding energy (−1.11 kcal mol⁻¹) than the Ag atom (−0.19 kcal mol⁻¹) when docked to protein Mre-11. The findings indicate that Torenia-mediated AgNPs are safe and possess multifunctional properties suitable for bioremediation, wastewater treatment, and pharmaceutical applications. This study provides the first report of AgNP synthesis using five varieties of Torenia fournieri, highlighting the originality of this plant-based approach and its promise for sustainable nanotechnology.