In vitro Evaluation of Antioxidant and Antibacterial Activities of Eco-friendly Synthesized Silver Nanoparticles using Quercus robur Bark Extract

Abstract

Aims: This study reports a simple, cost-effective, and environmentally friendly method to obtain silver nanoparticles (AgNPs) using an aqueous extract of Quercus robur bark.

Methods: AgNPs synthesis conditions such as silver nitrate concentration, extract:AgNO₃ volume ratio, pH, temperature, and reaction time have been examined. After optimizing the synthesis, the obtained AgNPs were characterized by different methods such as UV-Vis, TEM, EDX, and FTIR. The antioxidant activity was evaluated using lipoxygenase inhibition capacity and inhibition of erythrocyte hemolysis mediated by peroxyl free radicals tests. The antimicrobial potential of the samples was tested against Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans.

Results: The AgNPs synthesis process is influenced by reaction conditions, the optimum established values being, in this case: concentration of 3 mM AgNO₃, 1:9 extract: AgNO₃ volume ratio, pH value of 6, 60 ºC temperature, and 90 minutes stirring time. The shape of the synthesized AgNPs was predominantly spherical, with an average size of 50 nm. The SPR band at 432 nm, the strong EDX signal at ~ 3 keV and the zeta potential of -13.88 mV revealed the formation of AgNPs and electrostatic stabilization of the colloidal solution. FTIR analysis confirmed the participation of molecules from the extract in the synthesis and stabilization of AgNPs. The obtained nanoparticles showed improved antioxidant, antifungal and antibacterial activities compared to the extract.

Conclusion: The results open the possibility of exploring new applications of nanoparticles obtained via green synthesis.

Keywords: Antioxidant activity; Quercus robur; antimicrobial activity; green synthesis; physicochemical characterization; silver nanoparticles.