Abstract: By fractional ultrafiltration followed by DEAE-52 anion-exchange column chromatography, an enzymatic hydrolysate of Crassostrea rivularis was fractionated into three polysaccharides named CRP-1, CRP-2 and CRP-3. The molecular masses and purity of the polysaccharides were determined by high performance gel permeation chromatography combined with Sephadex G-100 column chromatography, and their structures were elucidated by determining glycosyl groups as well as using high performance liquid chromatography and Fourier transform infrared (FTIR) spectroscopy. The results showed that the total sugar content of CRP-1 was (32.40 ± 0.89)% with a molecular mass of 124.5 kDa. It was composed of mannose, ribose, glucosamine, glucuronic acid, galacturonic acid, glucose, galactosamine, galactose, arabinose, with a molar ratio of 5.55:0.32:9.08:0.47:0.66:48.13:3.57:8.53:0.30. The total sugar content of CRP-2 was (78.50 ± 1.90)% with a molecular mass of 67.0 kDa. CRP-2 was composed of mannose, ribose, glucosamine, glucose, galactose and galactose with a molar ratio of 7.79:0.41:12.69:32.08:4.98:15.92. The total sugar content of CRP-3 was (73.46 ± 2.19)%, with a molecular mass of 8.3 kDa. It was composed of glucosamine, galactose acid and glucose with a molar ratio 8.91:5.71:10.15. FTIR analysis showed that CRP-1 was a polyaldehyde pyranoside. CRP-2 was an unsaturated polyhydroxyketone while CRP-3 was a polyunsaturated polyhydroxyketone containing carboxyl groups. All the polysaccharides displayed immunomodulatory activity in mouse macrophage line RAW264.7.

Key words: Crassostrea rivularis, polysaccharides, structure, immunoregulatory activity