Green synthesis, characterisation, and antibacterial activity of silver nanoparticles obtained from Salvia officinalis extract

The present study investigated the properties and antimicrobial activity of silver nanoparticles synthesised through a green method using Salvia officinalis. Extracts were obtained from sage at two different temperatures, and these extracts were then used to synthesise silver nanoparticles through a reaction with AgNO₃. The characteristics of resulting silver nanoparticles and their antimicrobial effects on foodborne pathogenic bacteria were examined. During the synthesis, the colour of the silver nanoparticle solution changed from yellow to dark brown, and a significant absorbance peak was observed at 360 nm. The sizes of the synthesised silver nanoparticles were found to be 53.77 and 57.08 nm for the two different extraction temperatures, respectively. The nanoparticles exhibited spherical-rod shapes with silver contents of 83.91% and 84.38% and crystal sizes of 37.15 nm and 34.81 nm, corresponding to the two temperatures. The reduction of silver ions involved functional groups like C=C or C=O. The antimicrobial activity of the synthesised silver nanoparticles was evaluated at concentrations of 10 and 25 mg.mL-1 using the paper disc method against several foodborne pathogenic bacteria. Notably, the sage extract displayed antimicrobial efficacy against Salmonella Typhi, Listeria monocytogenes, and Staphylococcus aureus. However, no significant antimicrobial effect was observed against Escherichia coli O157:H7.