Free-radical-scavenging activity and antioxidant effect of ascophyllan from marine brown algae Padina tetrastromatica

Brown seaweeds are rich in sulfated polysaccharides that could potentially be exploited as functional ingredients for human health. Over the years, sulfated polysaccharides with potential pharmacological, nutraceutical and functional food properties have been isolated from brown seaweeds. This study was designed to characterise and evaluate the antioxidant activity of a sulfated polysaccharide ascophyllan isolated from marine brown algae Padina tetrastromatica. Four polysaccharide fractions were purified from crude ascophyllan. Antioxidant activities of the polysaccharide fractions were evaluated by various in vitro assay systems, including 2,2-diphenyl-1-picrylhydrazyl (DPPH), superoxide anion, hydroxyl radical-scavenging activity, lipid peroxidation and reducing power assay. The results showed that the ascophyllan fraction AF3 showed stronger free-radical-scavenging abilities and had good antioxidant effect. Available data obtained by in vitro models suggest that there is a correlation between the sulfate content and antioxidant activity.