Population based studies suggest that dietary fat is not associated directly with increased risk of colonic cancer, although several conditions can develop in the gastrointestinal system because of high fat intake. A surgical model was developed to study the effect of oxidative modified bile on colonic mucosa in hyperlipidemic rats as well as the effectiveness of natural product "Raphacol" bile granule. 150-200 g Wistar rats were treated with lipid rich diet (2% cholesterol, 20% sunflower oil, 0.5% cholic acid supplementation) and/or Raphacol (2 g/bwkg) in drinking water for 10 days. The common bile duct was cannulated and bile was collected and injected into the lumen of proximal and distal parts of colon for 30 minutes. Redox parameters were measured and electronmicroscopical study was carried out. Free SH-group (0.1132 +/- 0.034/0.096 +/- 0.0065 mmol/l) and reducing power (1169.49 +/- 97/871.25 +/- 157.61 nmolAS) of colonic mucosa were significantly decreased in hyperlipidemy. When bile from hyperlipidemic rats was injected on the bowel, the free SH group (0.1757 +/- 0.0228/0.1932 +/- 0.0398 mmol/l) and the proton donor activity (0.2669 +/- 0.0431/0.3333 +/- 0.013%) decreased comparing to the effect on colonic mucosa of bile from control animals. In animals treated with Raphacol, the damage of mucosa was moderate in both (hyperlipidemic and bile treated) experiments. Our results show that enteral antioxidant treatment can protect against the destructive mechanism of dietary fat and oxidative modified bile in hyperlipidemy.