Antioxidant activity of sulfated polysaccharide fractions extracted from Undaria pinnitafida in vitro

Two sulfated polysaccharide fractions (S1 and S2) were successfully isolated from seaweed Undaia pinnitafida and the chemical characteristics were determined. Antioxidant activities of the polysaccharide fractions were evaluated by assays of various antioxidants in vitro systems, including superoxide anion, 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl radical-scavenging activity and metal chelating ability. The results showed that the two sulfated polysaccharides contained rhamnose as the major neutral sugar and present high sulfate content (33.99–34.29%). Antioxidant assays suggested that the two sulfated polysaccharide fractions (S1 and S2) possessed good antioxidant properties and had stronger antioxidant abilities than de-sulfated polysaccharides (DS-1 and DS-2). Available data obtained by in vitro models suggested that the correlation between the sulfate content and antioxidant activity was positive.