Purification and characterization of an antioxidant protein from Ginkgo biloba seeds

A new antioxidation protein named G4b was purified from Ginkgo biloba seed albumin. The results of chemical colorimetry and chemiluminescence methods showed that the hemi-inhibitory concentration (IC50) of G4b on the hydroxyl radical were 78.1 μg/mL and 115.1 μg/mL, and the IC50 on DPPH was 100.7 μg/mL, while the IC50 on the superoxide anion and DNA injury were 23 μg/mL and 27 μg/mL, respectively, and the abundance of sulfur amino acids and aromatic amino acids contained in G4b might contribute to its strong antioxidation properties. G4b is a kind of homogeneous and novel protein with a molecular mass of 29,247 Da, consisting of two peptides with similar molecular weights linked by a disulfide bond. Result of β-elimination reaction showed that G4b is connected with a small quantity of polysaccharide by an oxygen-glucosidic bond.