Effect of carboxymethylation on antioxidant properties and radical degradation of mannans and glucans

Carboxymethyl derivatives (CM-derivatives) of α,β-mannans from yeasts, Saccharomyces cerevisiae β-glucan and dextran (α-glucan) were found to possess strong antioxidant activities against reactive hydroxyl radicals (OH) compared to underivatized polysaccharides. When CM-derivatives having similar DS (0.41–0.45) were compared, the antioxidant activity decreased in order CM-mannan > CM-β-glucan > CM-dextran. Moreover, the antioxidant activities against OH increased with increasing degree of substitution (DS) of polysaccharides. The CM-mannan and CM-dextran with the highest DS (0.73 and 1.1, respectively) were the strongest antioxidants and their degradation by OH decreased with increased carboxymethylation. The scavenging abilities of CM-polysaccharides against stable DPPH radical (DPPH) were lower than those of original underivatized ones. Also this scavenging property against DPPH was lower compared to antioxidant effect against OH.