A Method for Detecting Antioxidant Activity of Antioxidants by Utilizing Oxidative Damage of Pigment Protein

A simple and effective method for detecting the antioxidant activity by utilizing oxidative damage of pigment proteins was developed. In this method, phycocyanin and bovine hemoglobin pigment proteins were used as substrates attacked by free radicals; AAPH was used as a free radical initiator; and Trolox as a positive control; and the fermentation products of Lactobacillus plantarum 793, phycocyanin hydrolysates, salmon skin collagen hydrolysates, and synthetic peptides PMRGGYHY and FCVLRP are antioxidants inspected in this study. Because of being attacked by free radicals, the absorbance of the pigment proteins at their characteristic absorption peak changes with time. By recording the time-varying curve at the characteristic absorption peak of the pigment protein in the blank/negative control sample, the Trolox positive control sample, and the samples of inspected antioxidants, the antioxidant activity could be calculated by using the specific equation. The linear detection ranges of Trolox in the phycocyanin assay and the bovine hemoglobin assay were 1–4 μM and 4–24 μM, respectively. Compared with the ORAC assay, the antioxidant activities of the samples measured by this method were slightly lower. The method proposed in this study reflects the protective effects of inspected antioxidants on pigment proteins, which could potentially serve as new biomarkers of oxidative damage processes.