Antioxidant activities of fucoidan degraded by gamma irradiation and acidic hydrolysis

• Antioxidant activity of fucoidan degraded by gamma-irradiation was analyzed.
• Degree of change of antioxidant activity was dependent on the measuring method.
• Acid hydrolyzed fucoidan was compared to gamma-irradiated for its antioxidant activity.

Low molecular weight fucoidan, prepared by radical degradation using gamma ray was investigated for its antioxidant activities with different assay methods. As the molecular weight of fucoidan decreased with a higher absorbed dose, ferric-reducing antioxidant power values increased, but β-carotene bleaching inhibition did not change significantly. The antioxidant activity of acid-degraded fucoidan was also examined to investigate the effect of different degradation methods. At the same molecular weight, fucoidan degraded by gamma irradiation showed higher 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity than that observed with the acidic method. This result reveals that in addition to molecular weight, the degradation method affects the antioxidant activity of fucoidan.