Potential antioxidant and chemical characterization of sulfated polysaccharide from the red seaweed (Gracilaria birdiae)

Abstract

There has been an increasing interest in biological activity of sulfated polysaccharides from marine algae due to alleged anticoagulant, antioxidant and antithrombotic activities. Marine red algae of the genus Gracilaria are a major agarophyte resource in the world and are cultivated for the phycocolloid industry or for integrated marineculture. In this work, a polysaccharide was isolated by an aqueous extraction from the red seaweed Gracilaria birdiae (Gb), with a yield of 27.2%. The sulfate content of polysaccharide was 8.4 % and it is composed mainly by galactose (65.4% mol), 3,6-anhydrogalactose (25.1% mol), and 6-O-methylgalactose (9.2% mol). The analysis through gel permeation chromatography showed that Gb has a heterogeneous system, with a molar mass at the principal peak of 2.6 x 106 g/mol and a shoulder of 3.7 x 105 g/mol. The sulfated polysaccharide of Gb characterized by FTIR exhibits the characteristic bands of agarocolloids (at 1372 and 770 cm-1). The rheological behaviour of Gb sulphated polysaccharide was evaluated and compared to that of commercial agar. The results showed that the sulfated polysaccharide of Gb exhibit a gel-like behaviour close to the one displayed by commercial agar. DPPH free-radical scavenging effect of each sample was measured; the results obtained demonstrated that the sulphated polysaccharide had a moderate effect on inhibiting the formation of these radicals Gb sulphated polysaccharide can be an alternative to commercial agar for applications such as a gelling agent in food industry as shown by their rheological behaviour and significant antioxidant activity.