The mechanism for cleavage of three typical glucosidic bonds induced by hydroxyl free radical

A novel mechanism for cleavage of three typical α(1 → 2), α(1 → 4) and β(1 → 4) glucosidic bonds induced by hydroxyl free radical was examined with DFT theory at B3LYP/6-31 + G(d,p) level using PCM water solvent model. It was found that the hydrogen abstraction from the CH bonds outside the saccharide rings could induce the hydrogen transfer from the hydroxyl at the radical carbon to the oxygen atom of saccharide ring with the mediation of water, which led to the opening of saccharide ring and the breakage of glucosidic bonds. Alternatively, the hydrogen in COH outside the saccharide ring of maltose and sucrose could also transfer to the adjacent glucosidic oxygen atom with a water molecule mediation to make glucosidic bond break directly. Based on this study, it can be well explained the experimental results that the oxidation of some oligosaccharides with hydroxyl free radicals can produce molecules of glucose, fructose and other monosaccharides.