Green synthesis of silver nanoparticles (AgNPs) using leaf extracts of hibiscus and night jasmine and evaluation of their antimicrobial activities

The biosynthesis of silver nanoparticles (AgNPs) with plant-based extracts has emerged as a sustainable, cost-effective, and environmentally friendly alternative to conventional chemical synthesis processes. Indian medicinal plants serve as potential sources of natural reducing and stabilizing agents essential for AgNP formation. AgNPs were synthesized using 1 mM aqueous AgNO₃ and 5% leaf extracts of Tagetes erecta (Marigold) and Tridax procumbens (Tridax). The formation of AgNPs was confirmed by a visible color change and UV–Vis spectrophotometric analysis. The antimicrobial efficacy of the synthesized AgNPs was evaluated against Escherichia coli, Bacillus sp., and Aspergillus niger. Their potential for water disinfection was further assessed using samples collected from river, pond, and canal sources. Both Marigold- and Tridax-derived AgNPs exhibited enhanced antimicrobial activity compared to AgNO₃ and crude plant extracts. Marigold-mediated AgNPs demonstrated slightly higher inhibition zones against Gram-positive (Staphylococcus aureus, Klebsiella pneumoniae) and Gram-negative (E. coli) bacteria, as well as A. niger. In water disinfection studies, the synthesized AgNPs achieved over 50% bacterial growth reduction. The study highlights the strong bio-reducing capacity of plant-derived compounds in generating AgNPs with notable antimicrobial and disinfection properties. Marigold extract exhibited marginally higher efficiency, making it a promising candidate for green nanoparticle synthesis. Further investigation is required to evaluate the long-term environmental impacts, stability, and cytotoxicity of the synthesized AgNPs. The objective of this study is to establish a sustainable and eco-compatible approach for synthesizing AgNPs with potential applications in antimicrobial treatment and water purification.