Antioxidant and DNA protection activities of a glycoprotein isolated from a seaweed, Saccharina japonica

Summary A glycoprotein with a molecular weight of ∼10 kDa was purified from Saccharina japonica , and its antioxidant activity was evaluated using five different antioxidant assays. The highest antioxidant activities of the purified glycoprotein determined by DPPH, ABTS, SODA, SORS and FRAP assays were 85%, 95%, 94%, 72% and 97%, respectively. About 37% nitric oxide scavenging and 85% xanthine oxidase inhibition activities were also observed at a concentration of 5 mg mL −1 . The glycoprotein exhibited optimal activity levels of free radical scavenging at pH 7–9 and 40 °C. Antioxidant activity decreased when treated with ethylenediaminetetraacetic acid and metal ions. Moreover, its scavenging activity decreased when the glycoprotein was treated with deactivation agents such as pronase E or sodium periodate (NaIO 4 ), and it showed protective activity against DNA cleavage induced under oxidative conditions.