Characterization of porphyran from the edible seaweed Nori and its efficient preparation and application

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1. We have established an efficient preparation method of highly purified porphyran from Nori. Its yield was more than 20 % of dry Nori. This method can be easily scaled up for industrial preparation of porphyran.2. We have developed a new gas chromatographic method for the compositional analysis of algal galactans containing 3,6-anhydrogalactose (AG), which could not be chromtographically, analyzed since it is readily destroyed in usual acid hydrolysis and methanolysis. We carried out mercaptolysis of galactans under an anhydrous condition using the newly developed solvent system, an ethanethiolic HCl solution. This permits quantitative releases of component sugars including AG, followed by trimethysilylation and gas chromatography. This new analytical method has enabled the elucidation of detailed chemical properties and structure of porphyran.3. We have devised a method to chemically evaluate the quality of Nori from the sugar composition of Nori.4. We have demonstrated that porphyran is remarkably heterogeneous in its molecular size, sugar composition, and sulfate content.5. We have revealed the cause of remarkable heterogeneity of porphyran by demonstrating the occurrence of "polygalactose" structure.