Characterization and Biological Activity of Silver Nanoparticles Synthesized from Sargassum aquifolium: A Sustainable Approach

Background: Algal extracts provide efficient route for green synthesis of nanoparticles. Objectives: This research aims to biosynthesize silver nanoparticles (AgNPs) using Sargassum aquifolium extract and to evaluate their antioxidant and antimicrobial potential. Methodology: The synthesis was initiated by the reduction of silver ions with functional groups in S. aquifolium extract. The antimicrobial and antioxidant activities were tested using well diffusion assay DPPH assay. Results: UV-Vis spectrometry revealed absorption maxima at 521 nm for the synthesized AgNPs, compared to 470 nm for the algal extract. Transmission electron microscopy indicated that AgNPs were spherical or pentagonal, with a size ranging from 6.48 to 9.80 nm and a zeta potential of -15.6 mV, indicating relative stability. Fourier transform infrared spectroscopy affirmed the involvement of certain groups in the capping and stabilization of the AgNPs. There was a decrease in total phenolics and flavonoids in the formed nanocomposite than the main algal extract due to their involvement in the reduction process. The algal extract and nanocomposite formed expressed significant antioxidant scavenging activity. The antimicrobial efficacy of the extract and AgNPs were evaluated against various microbial pathogens that are Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella typhi, Bacillus subtilis, Escherichia coli, Klebsiella pneumonia, and Candida albicans. The results revealed broad antimicrobial spectrum against all the screened species. Additionally, fatty acid analysis identified palmitic acid, oleic acid and linoleic acid as the predominant fatty acids. Conclusion: These findings underscore the importance of S. aquifolium as a source of natural antimicrobials and in green nanotechnology applications.