Flora Lam Kim1,2, Valérie Stiger-Pouvreau2, Cecilia Biancacci1, Alecia Bellgrove1
1Deakin University, School of Life and Environmental Sciences, Centre for Integrative Ecology, Warrnambool Campus, Warrnambool, Victoria 3280, Australia
2Laboratoire des Sciences de l’Environnement Marin (UMR 6539), Institut Universitaire Européen de la Mer, Université de Bretagne Occidentale, rue Dumont d’Urville, 29280 Plouzané, France
While seaweeds have traditionally been important in East-Asian diets for centuries, seaweed consumption remains under-exploited in Western countries, despite demonstrated antioxidant activity and health benefits. Natural antioxidants are valuable to the food industry because they are non-toxic food preservatives that can prevent various diseases. High antioxidant activity has been reported for phlorotannins that act as eco-defensive molecules and are particularly abundant in fucoid brown algae. We hypothesised that intertidal and shallow-subtidal Australian fucoids may be rich in antioxidant phlorotannins at levels suitable for exploitation, due to high solar- and UV-radiation exposure. We compared the radical-scavenging activity of purified phlorotannins extracts from four temperate Australian fucoids compared to that of five commercially exploited French fucoids, and positive antioxidant controls (vitamin C, BHA (Butylated hydroxyanizole) and BHT (Butylated hydroxytoluene)), using ORAC (Oxygen Radical Absorbance Capacity), DPPH (2,2-Diphenyl-1-picrylhydrazyl) and FRAP (Ferric Reducing Antioxidant Power) assays. Results showed high radical-scavenging activity of phlorotannins for all seaweeds studied, but with significant differences between species, and some differences among assays. All three tests highlighted the high activity of phlorotannins from the Australian fucoid Cystophora torulosa, showing no difference with BHA, but significantly better activity than vitamin C and BHT. The ORAC assay also suggested interesting activity for Hormosira banksii and Phyllospora comosa extracts. Finally, the Australian fucoids extracts had comparable or higher activity relative to exploited French fucoids. This study reveals interesting antioxidant properties in novel Australian species, warranting further investigation into the commercial applications and sustainability of these seaweed polyphenols for food and food products.