Structural characterization and antioxidant activity of a glycoprotein isolated from Camellia oleifera Abel seeds against D-galactose-induced oxidative stress in mice.

• A glycoprotein (COG2a) from Camellia. Oleifera Abel seed exhibits antioxidant activity. • COG2a has the characteristic structure of an O-linked glycoprotein. • COG2a protects against D-galactose-induced oxidative damage in vivo. A bioactive glycoprotein (COG2a) was isolated from the seeds of Camellia oleifera Abel by multiple column chromatography and its structure and antioxidant capacity were investigated in vitro and in vivo. Structural analysis of COG2a revealed that it was an O-linked glycoprotein with a molecular mass of 25.9 kDa. The protein and carbohydrate contents of COG2a were 54.28% and 45.29% respectively, and its carbohydrate moieties were mainly rhamnose, arabinose, xylose, mannose, glucose, and galactose at a molar ratio of 1.29:1.65:5.81:1:16.15:14.47. Fourier transform infrared and circular dichroism spectra of COG2a exhibited the typical characteristics of a glycoprotein, that is, 80.3% α-helix, 1.0% β-strand, 6.4% β-turns, and 15.8% unordered residues. COG2a exhibited concentration-dependent free radicals-scavenging capacity in vitro. COG2a also significantly enhanced the SOD and GSH-PX activities and reduced the MDA and total carbonyl contents in blood and liver tissues of D-galactose-induced mice to protect against oxidative stress. [ABSTRACT FROM AUTHOR]