Extraction, purification, and structure characterization of polysaccharides from Crassostrea rivularis.

Crude polysaccharide was prepared from Crassostrea rivularis by 30% (w/v) potassium hydroxide solution at 90°C for 120 min. Three fractions (OG1, OG2, and OG3) were purified by DEAE-52 cellulose and Sepharose 2B gel column chromatography. The chemical structures were determined using gas chromatography (GC), high-performance gel permeation chromatography (HPGPC), Fourier-transform infrared (FT-IR) spectroscopy, and (1)H and (13)C nuclear magnetic resonance (NMR) spectroscopy. The results indicated that OG1 was composed of rhamnose and little mannose (8.71%), the ratio of Rha: Gal: Xyl: Fuc in OG3 were 14:5.5:3:1. And their average molecular weights (Mw) were about 1.66 × 10(6) and 2.33 × 10(6) Da, respectively. OG2 was composed only of glucose (98.23%), which means it was glycogen. OG2 was consisted mainly of →4)- α-D-Glc-(1→, with the branch chain every 6.5 glucose residues on average, which is →4,6)-α-D-Glc-(1→ and trace amount of α-D-Glc-(1→ branched units. The Mw was 2.27 × 10(6) Da. It provides the bases for the bioactivity research.