Effects of Molecular Weight and Ratio of Guluronic Acid to Mannuronic Acid on the Antioxidant Properties of Sodium Alginate Fractions Prepared by Radiation-induced Degradation

In this study, the effects of the molecular weight and ratio of guluronic acid (G) to mannuronic acid (M), G/M, of some sodium alginate (NaAlg) fractions on their antioxidative properties were investigated. Low-molecular-weight-fractions with various G/M were prepared by gamma radiation-induced degradation of NaAlg. Change in their molecular weight was monitored. Antioxidant properties of the fractions with various molecular weight and G/M were evaluated by determining the scavenging ability of 1,1-diphenyl-2-picrylhydrazyl free radical (DPPH()). 50% inhibition concentrations of the 50 kGy-irradiated NaAlgs having molecular weights of 20.5, 17.7, and 16.0 kDa were found to be 11.0, 18.0, and 24.0mg/ml, respectively, whereas the fractions of the same molecular weight with a lower G/M exhibited a better DPPH() scavenging activity. The results demonstrated that its molecular weight and G/M were important factors in controlling the antioxidant properties of NaAlg.