Bio-inspired Synthesis of Silver and Zinc Oxide Nanoparticles Using Syzygium salicifolium: Unveiling Versatile In Vitro Biomedical and Photocatalytic Applications

This study reports the synthesis and applications of silver (SS-AgNPs) and zinc oxide (SS-ZnONPs) nanoparticles from the leaf extract of Syzygium salicifolium, and its comprehensive characterisation using UV–Visible spectroscopy, Fourier Transform Infrared spectroscopy (FT-IR), Dynamic Light Scattering (DLS), Zeta Potential, X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), and Field Emission Gun Transmission Electron Microscopy (FEG-TEM). UV–Visible spectroscopy revealed characteristic absorption peaks at 419 nm (SS-AgNPs) and 370 nm (SS-ZnONPs), with zeta potentials of − 16.24 and − 16.91 mV, respectively. XRD confirmed crystallinity, while FE-SEM revealed distinct morphologies, and FEG-TEM determined particle size of 21.52 ± 4.93 nm and 20.82 ± 6.34 nm. SS-AgNPs exhibited pronounced antimicrobial activity against Escherichia coli (25.07 ± 0.95 mm), Staphylococcus aureus (20.4 ± 0.61 mm), Aspergillus flavus (25.50 ± 0.20 mm), outperforming SS-ZnONPs (8.5 ± 0.3 mm, 10.13 ± 0.12 mm, and 19.17 ± 0.21 mm, respectively). SS-AgNPs and SS-ZnONPs exhibited selective cytotoxicity against MCF-7 (IC₅₀: 11.11 vs. 26.78 µg/mL), HeLa (28.22 vs. 85.98 µg/mL), and A549 (138.44 vs. 140.59 µg/mL), with minimal toxicity toward HEK-293 cells. The hypoglycaemic activity showed α-amylase (IC₅₀: 74.86 vs. 73.20 µg/mL) and α-glucosidase (72.87 vs. 66.81 µg/mL) inhibition, while effective anti-inflammatory action against albumin denaturation (42.59 vs. 43.21 µg/mL) and membrane stabilisation (39.43 vs. 38.06 µg/mL) compared to diclofenac. SS-AgNPs achieved 64.82% methyl orange and 68.64% methylene blue degradation, while SS-ZnONPs reached 70.65 and 81.39%, respectively, with efficiency over five cycles. This pioneering study reveals the utility of Syzygium salicifolium as a sustainable precursor for multifunctional nanoparticles.