Biogenic Silver Nanoparticles via Hypericum calycinum L.: Synthesis, Characterization and Biological Effects

The green synthesis of biogenic nanoparticles using plant-derived compounds is regarded as an eco-friendly and sustainable alternative to conventional chemical methods, as it eliminates the need for toxic reagents and harsh reaction conditions. In this study, biogenic silver nanoparticles (AgNPs) were synthesized using the extract of Hypericum calycinum L., providing a cost-effective and environmentally friendly approach. A visible color shift from red to brown indicated the successful formation of H. calycinum-mediated silver nanoparticles (HCAgNPs). The nanoparticles were initially characterized via UV-Visible (UV-Vis) spectroscopy, which revealed a maximum absorption peak at 422 nm. Further analyses of particle morphology, size distribution, and elemental composition were conducted using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX). SEM images confirmed the formation of nanoparticles.The synthesized HCAgNPs demonstrated notable antimicrobial activity, particularly against Bacillus subtilis (ATCC 6633), among other tested strains such as Staphylococcus aureus (ATCC 25923), Pseudomonas aeruginosa (ATCC 27853), and Escherichia coli (ATCC 25922). Mutagenicity assessments indicated that HCAgNPs did not exhibit mutagenic effects. However, gel electrophoresis revealed DNA fragmentation at all tested concentrations. The antioxidant potential was evaluated using the DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging assay. Compared to the crude extract of H. calycinum, the antioxidant capacity of the silver nanoparticles was diminished. At the highest tested concentration (400 ppm), the inhibition rates were found to be 75.65% for the extract and 20.86% for the nanoparticles.