2.6. Measurement of antioxidant activity against OH-radical by protein degradation assay
The OH-radical solution was prepared immediately prior to the protein degradation assay as previously reported by Yanai, Shiotani, Hagiwara, Nabetani, and Nakajima (2008). Briefly, 1 ml of 0.13 M H2O2 was added to 0.1 ml each of 0.1 M EDTA, 0.1 ml FeCl3 2H2O, and 0.1 M ascorbic acid. The OH-radical concentration was expressed as the H2O2 concentration. Albumin dissolved in buffer saline at 0.57 mg/ml was used as the target protein.