GREEN SYNTHESIS OF METAL NANOPARTICLES USING FRUIT EXTRACTS: EVALUATION OF ANTIOXIDANT AND ANTIMICROBIAL PROPERTIES

Abstract

The increased need to obtain sustainable and environmentally friendly approaches to the fabrication of nanomaterial has stimulated studies on biogenic synthesis pathways. The current paper presents the green synthesis of silver nanoparticles (AgNPs) by using fruit extract of Punica granatum (pomegranate) as a natural reducing and capping agent in aqueous solutions. The best synthesis was done at pH 9, 60 C, and extract-salt ratio of 1:5 which was confirmed by a typical surface plasmon resonance (SPR) peak at 432 nm. X-ray diffraction (XRD) showed face-centred cubic (FCC) crystalline AgNPs with an average crystallite size of 18.4 ± 2.1 nm, which is in line with the transmission electron microscopy (TEM) measurements (mean diameter 20.3 ± 3.6 nm). Fourier-transform infrared spectroscopy (FTIR) was used to identify the phenolic hydroxyl (O -H, -3310 cm) and carbonyl (C -O, -1635 cm) stretches as the main functional groups that were the cause of reduction and stabilization. Colloidal stability was confirmed using dynamic light scattering (DLS) which gave a zeta potential of -31.4 mV. The produced AgNPs exhibited a high antioxidant activity (DPPH IC50 = 28.6 + 1.4 -1mL; ABTS IC50 = 24.1 + 1.2 -1mL), which is much higher than the crude extract itself. Agar well diffusion and broth microdilution assays of antimicrobials against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans demonstrated minimum inhibitory concentration (MIC) values of 12.550 µg/mL, with Gram-positive bacteria being more susceptible. These results make pomegranate-mediated AgNPs a scalable, non-toxic nanomaterial with potential biomedical uses.