Cells use antioxidant defense systems that include antioxidant enzymes, such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx), and molecules, such as glutathione, bilirubin, vitamins E and C, uric acid and creatine to defend against oxidative damage (5).
The antioxidants working in the defense systems act at four levels. The first line is the preventive antioxidants that prevent free radicals from forming. The second defense level is the antioxidants that find and suppress the active radicals. The third line of defense is the antioxidants that repair damage caused by free radicals. Lastly is adaptation, which occurs when the signal for free radical production induces the appropriate antioxidant to form and move to its needed location (6).