Assessment of the Antioxidant and Antibacterial Activities of Three Species of Edible Seaweeds

Extraction of secondary metabolites from St. Lawrence Estuary edible seaweeds – Saccharina longicruris, Ascophyllum nodosum and Ulva lactuca – was carried out by pressurized liquid extraction using ethanol. The antioxidant potential of extracts was evaluated through DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging, oxygen radical absorbance capacity and ferric reducing antioxidant power assays, and the antibacterial activity was tested against food spoilage bacteria: Escherichia coli, Micrococcus luteus and Brochothrix thermosphacta. Of all seaweed extracts, A. nodosum exhibited the highest phenolic and carotenoid contents, 50.2 mg GAE/g and 85 μg/g, respectively. A. nodosum also displayed the best DPPH scavenging activity, EC50 10.4 μg/mL, and best capacity to reduce ferric ion, 677.2 μmol TE/g dry weight at a concentration of 100 μg/mL. U. lactuca extracts showed the highest growth inhibition of E. coli, 69.5%; M. luteus, 61.4%; and B. thermosphacta, 21.4%. These findings suggest a high potential of St. Lawrence Estuary seaweed extracts for application in the food industry. Practical Applications Food producers, food industries, governments and consumers are aware of the importance to look into effective preventive measures in food quality and food safety fields. The decay of foods is caused by physical, chemical and biological factors, which leads to the loss of the organoleptic characteristics and consumer safety. Natural extracts combining both antioxidant and antibacterial activities can be used for further applications in reducing food spoilage and prolonging food shelf life. The majority of natural extracts could be approved as Generally Recognized As Safe (GRAS). St. Lawrence Estuary seaweed extracts possess high potential for application in the food industry using pressurized liquid extraction (PLE) method, which was selected for extraction efficiency purposes. In addition, production of seaweeds extracts using approved food-grade ethanol solvent by PLE method involves, on an industrial scale, cost savings.