Green synthesis of ZnO nanoparticles using <i>Centroceras clavulatum</i> and evaluation of their multifunctional biological activities and cytotoxicity

The study highlights the eco-friendly synthesis of zinc oxide (ZnO) nanoparticles utilizing an aqueous extract of the marine red alga Centroceras clavulatum and evaluation of their biofunctional properties. Phytochemical screening confirmed the presence of bioactive compounds such as phenols, flavonoids, alkaloids and terpenoids, with notable Total Phenolic Content (13.45 ± 0.57 mg GAE/g) and Total Flavonoid Content (64.95 ± 10.38 mg QE/g), supporting their role in nanoparticle formation. The synthesized nanoparticles were characterized using UV–visible spectroscopy (λmax = 373 nm and Eg = 3.06 eV), FTIR, DLS, XRD and FESEM–EDX, revealing crystalline, quasi-spherical nanoparticles with an average size of 64.9 nm and high purity. The biofunctional properties of the extract and ZnO nanoparticles were evaluated through in vitro assays. Antioxidant activity assessed by DPPH and phosphomolybdate assays demonstrating a significant free-radical scavenging capacity. Bovine serum albumin and egg albumin assays demonstrated considerable inhibition of anti-inflammatory action, whereas α-amylase and α-glucosidase inhibition studies demonstrated effective enzyme inhibition of antidiabetic activity. Antibacterial activity tested against Staphylococcus aureus and Escherichia coli showed concentration-dependent inhibitory effects. Cytotoxicity studies on NIH3T3 fibroblast cells indicated concentration-dependent moderate cytotoxicity. Overall, the results indicate that ZnO nanoparticles mediated by Centroceras clavulatum possess significant activities with potential biomedical applications.