Metabolism of the colonic mucosa of patients with ulcerative colitis (UC; n=31) and Crohn's disease (CD; n=26) and normal mucosa (control, n=26) was investigated using in vitro high-resolution proton magnetic resonance spectroscopy. Of the 31 UC patients, 20 were in the active phase and 11 were in the remission phase of the disease. Out of 26 CD patients, 20 were in the active phase, while 6 were in the remission phase of the disease. Twenty-nine metabolites were assigned unambiguously in the perchloric acid extract of colonic mucosa. In the active phase of UC and CD, significantly lower (P<or=.05) concentration of amino acids (isoleucine, leucine, valine, alanine, glutamate and glutamine), membrane components (choline, glycerophosphorylcholine and myo-inositol), lactate and succinate were observed compared to normal mucosa of controls. Patients in the active phase of UC and CD also showed increased level of alpha-glucose compared to normal mucosa. Altered level of metabolites indicates decreased protein and carbohydrate metabolism, thereby decreased energy status and deterioration of mucosa integrity during chronic inflammation. In the remission phase of UC and CD, the concentration of most of the metabolites was similar to controls except for lower values of lactate, glycerophosphorylcholine and myo-inositol in UC and Lac in CD. Formate was significantly lower in patients with the active phase of UC compared to patients with the active phase of CD, suggesting the potential of in vitro MRS in the differentiation of these two diseases.