Green Synthesis of Zinc Oxide Nanoparticles Using Brown Seaweed Padina boergesenii: Characterization, Nutritional Profiling, Phytochemical Analysis, and Evaluation of Antibacterial Activity against Pathogenic Bacteria

Background

Zinc Oxide Nanoparticles (ZnO NPs) offer broad-spectrum antibacterial activity, but conventional synthesis methods raise environmental and safety concerns. Green synthesis using marine algae like Padina boergesenii (P. boergesenii)., rich in bioactive compounds, provides a sustainable and eco-friendly approach to nanoparticle production.

Purpose

This study investigated the green synthesis of Zinc Oxide Nanoparticles (ZnO NPs) using the brown seaweed P. boergesenii and evaluated their antibacterial potential.

Materials and Methods

ZnO NPs were synthesized using an aqueous extract of P. boergesenii. The nanoparticles were characterized by UV-visible spectroscopy, Fourier-Transform Infrared Spectroscopy (FTIR), and X-ray Diffraction (XRD) analysis. Nutritional composition and phytochemical constituents of P. boergesenii were also determined. The antibacterial activity of the biosynthesized ZnO NPs was assessed against Escherichia coli, Staphylococcus aureus, and Pseudomonas sp. using a dose-dependent approach.

Results

The biosynthesized nanoparticles were characterized using UV-vis spectroscopy, showing a characteristic absorption peak between 300-350 nm, confirming successful ZnO NP formation. FTIR analysis revealed the presence of biomolecules acting as reducing and capping agents, while XRD patterns demonstrated high crystallinity matching the standard (JCPDS No. 36-1451). Nutritional profiling of P. boergesenii revealed significant levels of carbohydrates (48.76±1.6%), ash (33.56±1.4%), moisture (74.62±2.3%), protein (5.42±0.6%), and lipids (1.9±0.2%). Phytochemical screening confirmed the presence of alkaloids, flavonoids, saponins, phenols, cardiac glycosides, steroids, terpenoids, and quinones. Antibacterial assessment of the biosynthesized P. boergesenii-mediated ZnO NPs (Pb-ZnO NPs) demonstrated dose-dependent inhibition against Escherichia coli, Staphylococcus aureus, and Pseudomonas sp., with maximum activity observed at 100 μg/mL. Staphylococcus aureus showed higher susceptibility to the nanoparticles compared to the Gram-negative bacteria.

Conclusion

These findings highlight the potential of P. boergesenii as a natural source for synthesizing ZnO NPs with promising applications in biomedical and pharmaceutical fields, particularly as antimicrobial agents against pathogenic bacteria.