Colorimetric Determination of Singlet Oxygen Scavengers Using a Protein Photosensitizer

Despite the diverse roles of singlet oxygen (1O2) in plants and animals, simple detection of 1O2 has been limited due to technical difficulties. Here we report a colorimetric method for visualizing the generation and suppression of 1O2 using a protein photo-sensitizer, mini singlet oxygen generator (miniSOG). Upon external light irradiation, miniSOG strongly produced 1O2 and oxidized a universal chromogenic reagent, tetramethylbenzidine, leading to a rapid color change in solution. We used this finding to demonstrate the 1O2 scavenging effects of well-known anti-oxidants and of natural compounds extracted from plants. Owing to its high usability and simplicity, our developed assay platform will be useful for screening potential scavengers for reactive oxygen species and will promote the development of various antioxidants.