title: Oxidation of lactose with bromine.
abstract: Oxidation of lactose by bromine in an aqueous buffered solution was conducted as a model experiment to examine the glycosidic linkage cleavage occurring during the oxidation of oligosaccharides and polysaccharides. The resulting oxidation products, after reduction with sodium borodeuteride, were characterized by GLC-MS analyses of the per-O-methyl or per-O-Me3Si derivatives. Most of the products were carboxylic acids, of which lactobionic acid was major. Minor products, identified after partial fractionation on a BioGel P-2 column, comprised oxalic acid; glyceric acid; threonic and erythronic acids; tartaric acid; lyxonic, arabinonic, and xylonic acids; galactonic and gluconic acids; galactosylerythronic acid; galactosylarabinonic acid; galactosylarabinaric acid; galacturonosylarabinonic acid; and galactosylglucaric acid. No keto acids were identified. Galactose was detected as 1-deuteriogalactitol, the presence of which, together with the C6 aldonic acids, supported a galactosidic bond cleavage. Galactosylarabinonic acid was the major constituent (7.5%) among minors, and others constituted 0.2-3.7% of the principal lactobionic acid. These products together comprised 29% of the lactobionic acid, more than half (17%) of which were accounted for by the galactosidic linkage cleavage, supporting the significant decrease in molecular weight seen earlier in the bromine-oxidized polysaccharides by glycosidic cleavage.
authors.affiliation: Department of Biochemistry, College of Medicine, The University of Iowa, Iowa City, IA 52242, USA.
authors.forename: Byung Y
authors.initials: BY
authors.lastname: Yang
authors.forename: Rex
authors.initials: R
authors.lastname: Montgomery
mesh_terms: D001966:Bromine; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002264:Carboxylic Acids / Q000032:analysis; D002849:Chromatography, Gas; D007785:Lactose / Q000737:chemistry*; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000737:chemistry; D010084:Oxidation-Reduction; D011134:Polysaccharides / Q000737:chemistry*
chemical_list: D002264:Carboxylic Acids; D009844:Oligosaccharides; D011134:Polysaccharides; D007785:Lactose; D001966:Bromine