Characterization of Nutritional, Antimicrobial and Antioxidant Prop-erties of Five Seaweed Species in Sri Lanka

The present study assessed the nutritional, antimicrobial and antioxidant properties of five seaweed species in northern coast of Sri Lanka: Kappaphycus alvarezii, Sargassum wightii, Turbinaria ornata, Caulerpa peltata and Caulerpa racemosa. The proximate composition was measured in dried seaweed powder. The antioxidant properties were determined in seaweed water extracts as total phenolic content (TPC), total flavonoid content (TFC), 2, 2- diphe-nyl-1-picrylhydrazyl (DPPH) radical scavenging activity and ferric reducing antioxidant power (FRAP). Crude methanol and crude water extracts were examined for antimicrobial properties against four human pathogens; Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Candida albicans. The protein, fat, ash and gross energy con-tents varied from 4.7-26.5%, 0.02-0.05%, 7.6-25.6% and 10-18.7 kJg^-1, respectively. The two green seaweeds had the highest (p<0.05) protein and gross energy contents, while the other three species had higher (p<0.05) ash content. The TPC, FRAP and DPPH half maximal inhibitory concentration (IC₅₀) values ranged from 0.4-1.4 mg Gallic acid equivalent (GAE) g^-1 dry weight, 2923.3-9193.5 mM FeSO4 g^-1 dry weight and 1.5-8.5 mg mL^-1, respectively. The S. wightii showed the highest (p<0.05) TPC and FRAP, where-as K. alvarezii had the lowest (p<0.05) DPPH IC₅₀ value. No TFC response was observed. All seaweed methanol extracts showed antimicrobial activity against all four pathogens. The crude water extracts of K. alvarezii and T. ornata showed antimicrobial activity only against P. aeruginosa. Results showed that the selected seaweed species possess high nutritional, antioxidant, and antimicrobial properties. Therefore, they have the potential to be used in the food, pharmaceutical, and packaging industries.