Abstract: The refined polysaccharide was obtained from Porphyra yezoensis by ways as follows: degreasing, extraction, removing protein, ethanol precipitation, ultra-filtration and decoloring. Then, assayed by means of Molish and Fehling reaction, the intrinsic viscosity was obtained by diluting analysis in sequent order, and the contents of sulfate group assayed by Dodgson’s method. The contents of polysaccharide in Porphyra yezoensis were assayed by phenol-sulfuric acid method. Mean while the polysaccharide vs. galactose, or the converting factor was also made certain. The results showed that the method is simple, accurate and stable in 3h. Average recovery rate of the polysaccharide was 98.26% with 4.77% of RSD(n=5). The converting factor was 1.35. Excellent linearity appeared from 18.32μg to 54.96μg, with r=0.99945. With moderate intrinsic viscosity, [η] =34.26× 10-3ml/g, rather high contents of sulfate group were obtained as 21.63±0.11%(n=2).

Key words: Porphyra yezoensis polysaccharide, phenol-sulfuric acid method, intrinsic viscosity, sulfate group