title: Selective hydrolysis of the 3,6-anhydrogalacotosidic linkage in red algal galactan: a combination of reductive acid hydrolysis and anhydrous mercaptolysis.
abstract: Here we report a simple method for the structural analysis of red algal galactan containing 3,6-anhydrogalactose. Structural heterogeneity in the galactan was demonstrated by this method. For selective hydrolysis of 3,6-anhydrogalactosidic linkages in the galactan, conditions for reductive mild acid hydrolysis were examined by characterizing the resulting oligosaccharide alditols by anhydrous mercaptolysis. Residues other than alditols at the reducing ends, including labile 3,6-anhydrogalactose, were liberated quantitatively as diethyl dithioacetal derivatives, whereas alditols at the reducing ends were not derivatized and were liberated as alditols intact. The liberated sugars were then separated and measured quantitatively by gas-liquid chromatography. Heating of agarose in reductive hydrolysis with 0.3 M trifluoroacetic acid in the presence of an acid-stable reducing agent, 4-methyl morpholine borane, at 80 °C for 90 min and for 90 °C for 45 min was found to be optimum for the selective hydrolysis of 3,6-anhydrogalactosidic bonds, without detectable cleavage of other glycosidic bonds.
authors.affiliation: Department of Applied Biochemistry and Food Sciences, Faculty of Agriculture, Saga University, Saga, Japan. hamay@cc.saga-u.ac.jp
authors.forename: Yoichiro
authors.initials: Y
authors.lastname: Hama
authors.forename: Aya
authors.initials: A
authors.lastname: Tsuneoka
authors.forename: Ryoji
authors.initials: R
authors.lastname: Morita
authors.forename: Osamu
authors.initials: O
authors.lastname: Nomoto
authors.forename: Kenshi
authors.initials: K
authors.lastname: Yoshinaga
authors.forename: Hideo
authors.initials: H
authors.lastname: Hatate
authors.forename: Toshihisa
authors.initials: T
authors.lastname: Sumi
authors.forename: Hiroki
authors.initials: H
authors.lastname: Nakagawa
mesh_terms: D000143:Acids / Q000737:chemistry; D002241:Carbohydrates / Q000032:analysis; D002845:Chromatography; D005685:Galactans / Q000737:chemistry*; D005690:Galactose / Q000031:analogs & derivatives* / Q000737:chemistry; D006868:Hydrolysis; D008722:Methods; D015394:Molecular Structure; D019163:Reducing Agents / Q000737:chemistry; D000461:Rhodophyta / Q000737:chemistry*; D013438:Sulfhydryl Compounds / Q000737:chemistry
chemical_list: D000143:Acids; D002241:Carbohydrates; D005685:Galactans; D019163:Reducing Agents; D013438:Sulfhydryl Compounds; C117625:3,6-anhydrogalactose; D005690:Galactose