Comparison of antioxidant properties of sulfated polysaccharides from Ulva intestinalis

Abstract

The aim of this research was to compare the antioxidant properties of crude sulfated polysaccharide extracted from Ulva intestinalis. The conditions for extracting crude sulfated polysaccharide were investigated, including distilled water extraction at 80°C and acid extraction at various concentrations such as 0.1N and 1N HCI for 1, 3 and 6 h. The crude polysaccharide yields varied from 7.31 -12.96% depending on the extraction condition. Their sulfate content and molecular weight were determined in this study. The results showed the highest sulfate content was observed in hot water extraction for 6 h (39.99% ). The molecular weight of crude sulfated polysaccharide was determined by High- Performance Size Exclusion Chromatography (HPSEC). The average molecular weight of crude sulfated polysaccharide extracted by hot water and acid was 300 and 88 KDa, respectively. The antioxidant properties of crude sulfated polysaccharide extracted by hot water and acid were evaluated by several in vitro assays, including hydroxyl radical assay (OH•), 2,2-diphenyl-1 - picrylhydrazyl (DPPH• ), and azino-bis (3-ethyl benzothiazoline-6-sulfonic acid) (ABTS•+). The best DPPH• radical scavenging was found in crude sulfated polysaccharide extracted by 1 N HCI for 6 h (53.61%). The ABTS•+ and hydroxyl radical scavenging of crude sulfated polysaccharide extracted by 0.1 N HCI for 6 h showed good activity (83.25% and 73.25%, respectively). Crude sulfated polysaccharide extracted by hot water showed the highest sulfate contents, but antioxidant activity was lower than crude sulfated polysaccharide extracted by acid. Although molecular weights of polysaccharides influence their antioxidant activities, the antioxidant activities of crude sulfated polysaccharide were not a function of a single factor but a combination of several factors.