The degree of DNA damage in the human endothelial cell line ECV304 exposed to UV-C, with or without the presence of soybean oil (SBO), was assessed by the Comet assay. After 5-min exposure to UV-C, the %Tail DNA in the ECV304 cells ranged from 0% to 20% for SBO treatment groups and from 50% to 70% for the control group. The result indicated a strong protective effect of SBO against LTV-C-induced DNA damage. To clarity the mechanism of this protective effect of SBO, the methanol extract of SBO (MESO) was analyzed and its capacity against UV-C-induced DNA damage was evaluated. Gas chromatography mass spectrometry (GC-MS) analysis confirmed that MESO contained many antioxidants including n - 3-polyunsaturated fatty acid (n - 3-PUFA), tocopherols and phytosterols. Comet assay revealed that the MESO was also active, in reducing the DNA damage dose-dependently (P < 0.0001) vs. control in the ECV304 cells. Therefore, we concluded that these potential antioxidants may be responsible for the scavenge of oxidative radicals induced by UV-C irradiation. This study suggested that dietary SBO, which is abundant of antioxidants, may reduce the content or impact of reactive oxygen species (ROS) and lower the risk of diseases caused by ROS. (C) 2003 Elsevier Science B.V. All rights reserved.