Unlocking the bioactive potential: ZnO NPs synthesized from Chaetomorpha linum aqueous extract

Chaetomorpha linum is a green macroalgae genus known for its unbranched cylindrical cell filaments that are typically found in sea intertidal zones. Phytochemical screening of its crude and aqueous extracts revealed the presence of bioactive compounds such as flavonoids, steroids, tannins, saponins, and alkaloids, with flavonoids and steroids predominantly present in the aqueous extract. These phytochemicals acted as reducing and stabilizing agents for the green synthesis of ZnO NPs. UV–Vis absorption at 309 nm and a bandgap of 3.63 eV confirmed the formation of ZnO NPs. FTIR analysis identified functional groups including carboxylic acids, conjugated alkenes, and sulfones, correlating with the phytochemical constituents. X-ray diffraction revealed the semi-crystalline nature of the synthesized NPs, composed of both crystalline ZnO and amorphous organic matter. SEM analysis revealed that the ZnO NPs were spherical in shape, with diameters ranging from 15 to 35 nm. EDAX revealed the elemental composition of the NPs. DLS analysis showed an average size of 86.2 nm with a polydispersity index of 0.294, and a zeta potential of –28.7 mV indicated good colloidal stability. The antibacterial efficacy of the synthesized ZnO NPs was evaluated against various bacterial strains, demonstrating significant inhibitory zones, with Streptococcus mutans being the most susceptible among the tested strains. Furthermore, a protein denaturation assay revealed that the Chaetomorpha linum extract has dose-dependent anti-inflammatory activities, highlighting its potential for inflammation reduction. • Bioactive compounds were screened from green macroalgae Chaetomorpha linum. • ZnO NPs were synthesized using Chaetomorpha linum aqueous extract. • ZnO NPs characterized using UV-Vis, FTIR, XRD, SEM, and EDAX techniques. • Antibacterial and anti-inflammatory potentials of ZnO NPs were evaluated.