Evaluation of Antioxidative Activities of Polymeric Carbohydrates

Abstract

The antioxidant capabilities of various polysaccharides including alginate, β-glucan, chitosan, fucoidan and hyaluronate were investigated using three established assays: 2,2-diphenyl-1-picryhydrazyl (DPPH) radical scavenging, ferric reducing antioxidant power (FRAP), and superoxide dismutases (SODs) which are metalloenzymes that catalyze the dismutation of the superoxide anion to hydrogen peroxide and molecular oxygen. The DPPH radical scavenging assay revealed that among the five polysaccharides tested in this study, hyaluronic acid had relatively high antioxidant activity. However, low molecular weight chitooligosaccharides, consisting of glucosamine (GlcN)n, n = 6-9, exhibited slightly higher radical scavenging activity than hyaluronic acid. Interestingly, no DPPH radical scavenging activity was observed from the high molecular weight chitosan. On the contrary, in the FRAP activity measurements, high molecular weight chitosan showed the significant level of activity compared to the chitooligosaccharides, which has shown the similar activity of fucoidan and hyaluronic acid, although it was too marginal. Subsequently, fucoidan has shown the most significant antioxidant activity in SOD assay. These results suggest that antioxidant activity obviously depends on the molecular weight and their structural component as a key factor involved in each reaction mechanisms.