Effect of Polypodium leucotomos on acute, chronic and reactivated trinitrobenzene sulphonic acid colitis in rats

The effects were examined of a Polypodium leucotomos extract on trinitrobenzene sulphonic acid (TNBS) induced rat colitis. Pretreatment with the extract had a dose-dependent acute anti-inflammatory effect which was maximal at 100 mg/kg/day. This was characterized by preservation of glutathione levels at low doses (25-50 mg/kg) and inhibition of leukotriene B₄ synthesis at high doses (50-100 mg/kg). Treatment was also active in chronic colitis, induced by TNBS, as was evident by enhanced colonic fluid absorption and reducing myeloperoxidase levels, while glutathione levels and leukotriene B₄ synthesis were unaffected by treatment. Finally, treated animals were partially protected against colitis reactivation, showing lower myeloperoxidase and leukotriene B₄ synthesis than controls and normal fluid absorption, but no change in glutathione. In conclusion, Polypodium leucotomos is useful to control experimental colitis (acute, chronic and reactivated) but no common mechanism of action could be delineated, since neither an antioxidative mechanism nor inhibition of leukotriene B₄ synthesis can account for the overall effect.