Structural identification of principal polysaccharide component in water extract of Porphyra yezoensis Ueda

摘要

This work provided polysaccharide from Porphyra yezoensis Ueda for structural identification by biotechnological methods. Firstly, principal polysaccharide component was separated from P. yezoensis by water extraction and alcohol precipitation followed by chromatography. The component was identified as homogeneous polysaccharide by high performance liquid chromatography, optical rotation and ultraviolet absorption spectrophotometry. Then, structural identification was conducted by chemical methods, including periodate oxidation, reductive hydrolysis, gelatin nephelometry, methylation and desulfating analysis, and spectroscopic methods. Analysis showed that the polysaccharide component was composed of galactose (92%), as well as 3,6-inner ether galactose (3%) and 6-methyl galactose (5%) with substituents. The molecular weight was 246 kDa, and acidophobe percentage composition of 9%. It can be inferred that the polysaccharide was composed of precursor [(1→3)-β-D-galactose-(1→4)-6-OSO 3 -α-L-galactose] and repetitive units of agarobiose [(1→3)-β-D-galactose-(1→4)-3,6-inner ether-2-OCH 3 -α-L-galactose] and [(1→3)-β-D-galactose- (1→4)-α-L-galactose] in appropriate ratio of 9 : 9 : 1. Moreover, there were natural methoxy groups on the 2 nd position of galactose residue with 1, 4 connection and the 6 th position of galactose residue with 1, 3 connection.