Punica granatum: A plant with a high potential for the synthesis of silver nanoparticles

Abstract

O Objective: To use pomegranate (Punica granatum L.) extracts as a reducing agent for a simple and eco-friendly biosynthesis of silver nanoparticles and to test the latter’s antimicrobial potential against different bacteria. Methodology: The leaves and peel of ripe fruits of pomegranate were used to prepare aqueous and methanolic extracts to synthesize silver nanoparticles (AgNP). Then we evaluated these nanoparticles with techniques that allowed us to define their size, shape, and dispersion quality in aqueous media. To characterize the AgNPs we resorted to UV-Vis spectroscopy and dynamic light scattering (DLS). We determined their antimicrobial activity against Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis, and Staphylococcus aureus. Results: UV-Vis spectra were observed with absorption peaks at 425 nm for the nanoparticles synthesized with both aqueous and methanolic extracts. Regarding size, distribution, and dispersion in solution, the zeta potential shows that the surface charge in all cases is negative, with an average value ranging from -28.0 mV to -52.0 mV. Smaller nanoparticles were obtained from the aqueous extracts of the peel and leaves, with values between 1.42 - 2.96 nm, while the methanolic extracts yielded nanoparticles of 10 - 19.04 nm. Inhibition of microorganisms proved to be best against Escherichia coli, with a minimum inhibitory concentration (MIC) of 0.83 µg/mL up to 6.68 µg/mL. Conclusions: This study suggests that pomegranate extracts synthesize small-sized, well-dispersed silver nanoparticles with an almost spherical morphology, and good antimicrobial activity against gram-negative bacteria such as Escherichia coli.