Oxidation of amylose and amylopectin by hydroxyl radicals assessed by electrospray ionisation mass spectrometry

Abstract

The hydroxyl radicals (HO center dot) are one of the most reactive oxygen species (ROS) involved in the oxidative damage of biological molecules, including carbohydrates. During the industrial processing of food, ROS can be formed. In order to identify the structural changes induced in starch by oxidation, amylose, amylopectin, and maltotriose, an oligosaccharide structurally related to these polysaccharides, were subjected to oxidation with HO center dot generated under Fenton reaction conditions (Fe2+/H2O2). The oxidised polysaccharides were hydrolysed by alpha-amylase and the obtained oligosaccharides were fractionated by ligand-exchange/size-exclusion chromatography. Both acidic and neutral alpha-amylase resistant oligosaccharides were characterized by mass spectrometry. In oxidised neutral products, new keto, hydroxyl, and hydroperoxy moieties, and oxidative ring scission were observed at the reducing end of the oligosaccharides. The acid sugar residues occurred at the reducing end and included gluconic and glucuronic acid derivatives, and acids formed by oxidative ring scission, namely, arabinonic, erythronic, glyceric and glycolic acids. (C) 2016 Elsevier Ltd. All rights reserved.