The overall antioxidant activity of sections along the small intestine and colon of the rat was evaluated by determining its reducing power, which reflects the total antioxidant activity derived from low molecular weight antioxidant (LMWA), using cyclic voltammetry. In addition, the activity of the antioxidant enzymes catalase and superoxide dismutase (SOD), was measured in the same sections. It was found that the reducing power was higher in the mucosa/submucosa of the small intestine as compared to that of the colon. Similarly, catalase and SOD activity in the mucosa/submucosa of the small intestine was significantly higher than that of the colon. To improve their local antioxidant action catalase and SOD were cationized and their ability to treat colitis was compared to that of native enzyme preparations. The cationized antioxidant enzymes were found to be more effective than the native enzymes as a result of their ability to non-specifically adhere to the colonie mucosa. In most studies the cationized enzymes were more effective than 5-aminosalicylic acid and betamethasone.