Silver Nanoparticle Synthesis Using Bay Leaf Extract (Syzygium polyanthum) and Antibacterial Effectiveness Testing Against Staphylococcus aureus and Escherichia coli Bacteria

Abstract

The synthesis of silver nanoparticles (AgNPs) using bay leaf extract (Syzygium polyanthum) and their testing against bacteria aims to evaluate the antibacterial effectiveness on two types of bacteria, namely Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). The synthesis method used is environmentally friendly, with bay leaves serving as a reducing agent. The synthesis process was carried out by mixing silver nitrate (AgNO₃) solution with bay leaf extract at concentrations of 2 mM and 3 mM in a ratio of 1:30 and 1:40 between AgNO₃ and bay leaf extract. The use of bay leaf extract to create silver nanoparticles (AgNPs) was verified by a yellowish-brown color shift. UV-Vis spectrophotometry revealed that the absorbance was highest between 435 and 442 nm. Increased absorbance on day 7 compared to day 1 indicated better nanoparticle production and stability throughout time. At doses of 3 mM AgNO₃, antibacterial activity tests revealed greater inhibition zones; E. coli showed 12.7 ± 0.4 mm and S. aureus showed 15.4 ± 0.6 mm. Inhibition zones at two mM were 9.3 ± 0.3 mm for E. coli and 11.2 ± 0.5 mm for S. aureus. These findings demonstrate the potential of bay leaf extract as an environmentally acceptable ingredient for nanoparticle production and antibacterial applications by confirming the increased susceptibility of S. aureus to AgNPs. The antibacterial test using the disk diffusion method showed that silver nanoparticles have a significant inhibitory effect on the growth of both bacteria. A larger inhibition zone is formed at a concentration of AgNO₃ of 3 mM, with S. aureus being more sensitive to changes in concentration compared to E. coli. This result shows the potential of bay leaf extract as a natural and environmentally friendly antibacterial agent.