Eco-friendly synthesis of gallic acid-capped zinc oxide nanoparticles revealing antimicrobial, antioxidant, and anticancer activities

The present study aims to synthesized zinc oxide nanoparticles (ZnO NPs) in an sustainable approach by using gallic acid (GA) as a stabilising and bio-reductant. The synthesized GA-ZnO NPs were characterized by UV-Vis, FTIR, XRD, FE-SEM, and EDX, confirming their formation and structure. The nanoparticles demonstrated significant antimicrobial activity against both Gram-positive and Gram-negative bacteria, as well as the fungus C. albicans. The synthesized GA-ZnO NPs were confirmed by the UV-DRS spectrum, peak absorption exhibited at 320 nm is unique to ZnO NPs. FTIR data might prove that GA-ZnO NPs have phytochemical capping. The synthesized nanoparticles' average size was 33 nm based on the XRD pattern. The characterisation performed using a FE-SEM demonstrates the existence of GA-ZnO NPs in both hexagonal and spherical morphologies. The EDX data indicate the composition of Zinc (32 %) and Oxygen (63 %), exhibiting pronounced energy signatures accordingly. The antibacterial efficacy of ZnO-NPs demonstrated a maximal inhibition zone of (20.1 ± 0.48 mm) against C. albicans and (14 ± 0.66 mm) against S. aureus at a concentration of 100 μg/mL, respectively. Additionally, they exhibited strong antioxidant properties, with IC50 values of 282.5 µg/mL (DPPH assay) and 2.326 µg/mL (ABTS assay). The GA-ZnO NPs also showed notable cytotoxicity against cervical cancer (HeLa) cells, with an IC50 value of 34.71 µg/mL. Our study revealed that gallic acid exhibits broad-spectrum interaction with microbial and cancer cell targets, showing notable binding efficacy, especially against Staphylococcus aureus in comparison with other proteins. Toxicity profiling reveals it to be non-hepatotoxic, non-cytotoxic, and non-immunotoxic. These findings support its potential as a safe, moderately effective anticancer and antimicrobial agent.