STRUCTURAL IDENTIFICATION OF PRINCIPAL POLYSACCHARIDE COMPONENT IN WATER EXTRACT OF PORPHYRA YEZOENSIS

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-OSO3-α-L-galactose] and repetitive units of agarobiose [(1→3)-β-D-galactose-(1→4)-3,6-inner ether-2-OCH3-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 position of galactose residue with 1, 4 connection and the 6 position of galactose residue with 1, 3 connection. Introduction Polysaccharide is a macromolecule active substance widely existing in flora and fauna. At present, the ocean functional polysaccharide has become a new research hotspot. Porphyra yezoensis Ueda (Fam.: Bangiaceae) is mainly distributed in Liaodong Peninsula to coastal Fujian, China. Polysaccharide in P. yezoensis contains sulphate (Yoshizawa et al. 1995) which has functions of enhancing body immunity (Yoshizawa et al. 1995), antioxidation (Isaka et al. 2015), reducing blood fat (Qian et al. 2014), antineoplastic (Yu et al. 2015a), anti-inflammatory (Isaka et al. 2015), anti-radiation and anti-aging activities. Moreover, P. yezoensis can inhibit myofibrillar protein degeneration (Jiang 2014), reduce liver injury induced by carbon tetrachloride (Guo et al. 2007), adjust intestinal flora (Kawadu et al. 1995), promote lipid metabolism (Tsuge et al. 2004) and glucose metabolism in diabetics (Kitano et al. 2012). It also can be used as genetic vector of nanoparticles of positive ion (Yu et al. 2015b). In this work, the principal polysaccharide component was separated from P. yezoensis by water extraction and alcohol precipitation to identify its primary structure. Materials and Methods Porphyra yezoensis collected from Lvsi Marine Area, Jiangsu Province, China, was dried and triturated after washing with purified water. After 3 hrs of backflow in alcohol, P. yezoensis was dried in shade. Then, water was added in solid-liquid ratio of 1 : 50 (g/m), and filtration was conducted after heat at 100oC for 3 hrs. After being concentrated, the filtrate was centrifuged at . *Co-first author, **Author for correspondence: . National Demonstration Center for Experimental Fisheries Science Education (Shanghai Ocean University), Shanghai, 201306, China. Marine Biomedicine Institute, Second Military Medical University, Shanghai, 200433, China.