Bovine serum albumin was hydrolyzed with pepsin under suitable conditions. A peptide, having strong synergistic effect on conventional antioxidants such as α-tocopherol and sodium ascorbate, was successfully separated from the resulting hydrolysates by gel chromatography on a Sephadex G-25 column, ion-exchange chromatography on a SP-Sephadex C-25 column, and then high-performance liquid chromatography on an ODS column. This peptide appeared to consist of 21 amino acid residues.
