Structural Characterization Of Fucoidans From Hizikia Fusiforme

Fucoidans, polysaccharides that contain fucose, galactose, mannose, rhamnose, xylose and glucuronic acid, are one of the main constituents of Hizikia fusiforme, the hydroxyl groups of some monosaccharide residues were replaced by sulfate. It was difficult to analyze the structure of fucoidans on account of their complicated chemical compositions and larger MWs. Fucoidans have been widely studied due to their numerous biological activities in recent years. However, the relationships between the fucoidan structure and its biological ctivity have not yet been elucidated. To solve the scientific problem, the structure of fucoidans should be analyzed.In this paper, water-soluble polysaccharides were extracted with hot water and precipitated by80%ethanol from Hizikia fusiforme, referred to as WHFP (for water-soluble polysaccharides of Hizikia fusiforme), the yield of WHFP is20.4%. Water-soluble alginate was removed with4M CaCl2from WHFP, F were obtained, and the yield was3.7%. The phenol-sulfuric acid method, m-hydroxyldiphenyl method and Coomassie brilliant blue staining method were used to show the total carbohydrate content, uronic acid content and protein content was52.1%,6.4%and1.2%respectively.The crude F obtained was purified by DEAE-Sepharose CL-6B and Sephacryl S-400HR column, and the main polysaccharide fractions, F1-2and F2-2were collected, lyophilized and used for further analysis. The total sugar content, uronic acid content and crude protein content were measured by using methods as before. The sulfate groups content was estimated by barium sulfate turbidity. Monosaccharide compositions were determined by a PMP-HPLC method. The average molecular weight were determined by HPGPC with TSK-gel G-5000PWXL column. Protein and nucleic acid were detected by UV wavelength scanning.F1-2and F2-2has a single and symmetrical peak on Sephacryl S-400HR column revealing that they were homogeneous polysaccharides. The recovery rate of F1-2and F2-2is8.8%and32.6%based on F. The total carbohydrate content, uronic acid content, protein content and ester sulfate content of F1-2were59.8%,6.0%,0.8%and24.0%. For F2-2, the content is62.9%,5.2%,0.2%and19.5%in turn. The molar ratio of the monosaccharide composition of Fl-2was calculated to be Fuc:Gal:Xyl:GlcA:Man:Rha=67.9:15.8:8.2:3.7:2.6:1.8; in F2-2, the molar ratio shows Fuc:Gal:Xyl:GlcA:Man: Rha=68.6:20.4:5.9:2.6:1.6:1.0. The number average molecular weight of Fl-2and F2-2was estimated to be1.7×104Da and2.4×104Da, the weight average molecular weight of them was3.9×104Da and5.0×104Da, respectively. The absorption peaks of protein and nucleic acid were detected by UV wavelength scanning, show that there is trace protein and nucleic acid in F1-2and F2-2, in accordance with Coomassie brilliant blue staining method.The structure of F2-2was reported through methylation combined with FT-IR, GC-MS and NMR. The results showed that F2-2was composed of3-linked fucan with chains and branched at C-2or C-4, as well as β-Gal was found.