Rapid microwave-assisted green biosynthesis of silver nanoparticles using Picria fel-terrae Lour. extract: Characterization and antibacterial activity

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Green synthesis of silver nanoparticles (AgNPs) using plant extracts offers an environmentally friendly approach in which phytochemicals can contribute to nanoparticle formation and stabilization. This study aimed to synthesize AgNPs using an aqueous extract of Picria fel-terrae Lour. (AEPH) as a bioreducing and stabilizing agent, characterize the synthesized nanoparticles, and evaluate their antibacterial activity against Staphylococcus aureus . AEPH was prepared by heating for 30 min, and AgNP synthesis was optimized using microwave irradiation. Phytochemical profiling was performed using liquid chromatography–high-resolution mass spectrometry, while the synthesized AgNPs were characterized by ultraviolet–visible spectroscopy, particle size analysis, Fourier transform infrared spectroscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy, transmission electron microscopy, and X-ray diffraction. Antibacterial activity was evaluated using the agar disc diffusion method. The phytochemical profile revealed several organic acids and phenolic compounds that may contribute to Ag⁺ reduction and nanoparticle stabilization. The optimized synthesis conditions were 450 W and three irradiation cycles, producing a surface plasmon resonance (SPR) peak at 431 nm. Particle size analysis showed an apparent colloidal particle size of 62.61 nm, while transmission electron microscopy revealed primary particle dimensions of 27.27 ± 11.95 nm. The nanoparticles exhibited predominantly spherical to quasi-spherical morphology and a crystalline Ag-based structure, with a crystallite size of 21.132 ± 8.586 nm. AgNPs demonstrated antibacterial activity against S. aureus at all tested concentrations. These findings indicate that P. fel-terrae aqueous extract is a promising bioreducing and stabilizing agent for green AgNP synthesis with potential antibacterial applications.