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 (NaIO4), and it showed protective activity against DNA cleavage induced under oxidative conditions.