Andrea Iurlaro, G. Dalessandro, G. Piro
Dec 1, 2014
Citations
0
Influential Citations
8
Citations
Journal
Food Research International
Abstract
Abstract This study investigated the formation of oxo groups in pure solutions of barley mixed-linkage (1 → 3),(1 → 4)-β- d -glucans (MLGs) incubated in the presence of hydrogen peroxide or Fenton reaction-generated hydroxyl radicals ( OH), and it gives a fingerprint of products obtained after enzymic and acidic hydrolysis of OH-attacked MLG. Hydroxyl radical, but not hydrogen peroxide, introduced a range of NaB 3 H 4 -reducible functions into MLG chains. Driselase or lichenase digestion of NaB 3 H 4 -reduced MLGs released a complex mixture of 3 H-labelled products due to the presence of unusual and incompletely digestible residues in OH-attacked polysaccharide chains. Complete acid hydrolysis of OH-treated MLGs yielded a mixture of 3 H-aldoses (mainly glucose, mannose, galactose and allose) deriving from random OH attack at positions 2, 3 or 4 to form glycosulose residues which were NaB 3 H 4 -reducible to epimeric mixtures of 3 H-aldose residues. Furthermore, the production of [ 3 H]glucitol demonstrated the radical-mediated cleavage of mid-chain glucose residues to create new reducing termini. Oxidative scission of MLGs by hydroxyl radical caused a decrease in molecular weight of about 96%, which was partially inhibited by the addition of DMSO, an OH scavenger. The results can be a starting point for developing an assay to detect changes due to OH attack of MLGs in vivo , or during food processing and storage, based on the chemical or enzymic release of unusual sugar residues such as allose as diagnostic products after reduction/labelling treatment and partial purification (or selective digestion by lichenase) of polymeric material.