Riboflavin can be photosensitized to produce reactive oxygen species. In the present study, a DNA damage assay was developed based on the photo reaction of riboflavin. In this test system, oxyresveratrol showed higher DNA protective effect than the well-known antioxidants Trolox and ascorbic acid. The results suggest potential applications for oxyresveratrol as an anti-aging agent and a riboflavin stabilizer.