Preparation and antioxidant activity of the oligosaccharides derived from Laminaria japonica.

Hydrogen peroxide (H2O2) can degrade polysaccharides and has bleaching effect. In this study, the oligosaccharides derived from Laminaria japonica were prepared by hydrolysis with H2O2 and their antioxidant activity was investigated. The optimal hydrolysis conditions were determined as follows: reaction time 24h, reaction temperature 75°C, and H2O2 concentration 4%. Under the optimum conditions, the maximum yield of the oligosaccharides reached 17.65%, which was higher than that of aqueous extraction, and at the same time, the maximal decoloration rate reached 79.85%. The oligosaccharides sample contained 94.82% sugar, of which the average degree was approximately 8, and showed light green. The oligosaccharides derived from L. japonica showed high hydroxyl radical scavenging activity (91.31%) at the concentration of 100 μg/mL.