Phyto-fabrication of AgNPs using leaf extract of Vitex trifolia : potential to antibacterial, antioxidant, dye degradation, and their evaluation of non-toxicity to Chlorella vulgaris

The study assessed the bactericidal effects of green rapid biogenic synthesis of Vitex trifolia leaves AgNPs on MDR bacteria. The synthesis of AgNPs is indicated by a color change from yellow to dark brown. The ultra-visible spectrophotometer displays AgNPs at 430 nm max. This demonstrates that ions (Ag + ) were converted to silver (Ag), indicating the formation of silver nanoparticles. The synthesized nanoparticles were confirmed by their crystalline nature, shape, size, and functional groups via Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy dispersive X- ray spectroscopy (EDAX), and transmission electron microscopy (TEM). Biomolecules contain aqueous Vitex extract for capping and reducing the AgNPs. The nanoparticles have a face-centered cubic structure (FCC) crystallized. The antibacterial activity against Staphylococcus aureus , Vibrio cholerae , and Klebsiella pneumoniae exhibited a maximum zone of growth inhibition at 75 µg/mL. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of AgNPs against the clinically isolated pathogen S. aureus were 3.12 µg/mL and 4.5 µg/mL. Furthermore, time-dependent killing kinetic experiments showed that a 6 h AgNPs treatment was sufficient to fully inhibit all bacterial growth. AgNPs at a concentration of 250 µg/mL demonstrated antioxidant activity as measured by the FRAP and DPPH tests (85% and 90%, respectively). AgNPs demonstrated efficient photocatalytic activity in the degradation of methylene blue (MB) and achieved their highest photocatalytic activity (95%) after 2.30 h. Besides, the synthesis of AgNPs was targeted towards C. vulgaris algae, and exhibited deleterious effects even at larger concentrations. The chosen AgNPs concentration reduced chlorophyll, impeded algal development, and damaged the whole membrane system, as evidenced by the increased electrolyte leakage and malondialdehyde (MDA) and glutathione s-transferase (GSH) content after AgNPs exposure. Our report demonstrates that AgNPs V. trifolia have promising antibacterial, antioxidant, and potential dye degradation activities and can be employed in biomedical applications.