Effect of two artichoke extracts (36_U and 36_EB) on rat ileum (with respect to bowel syndrome) and the peristaltic threshold.

The diagnosis and treatment of irritable bowel syndrome (IBS) are complicated. Artichoke extracts are well known to be helpful in various gastrointestinal disorders. A hydrophilic extract 36_U mainly containing luteolin-7-glycoside, luteolin-7-O-glucoside, small amounts of cynarin and luteolin increased contraction of rat ileum. This is mainly mediated by 5-HT(3) - and 5-HT(2) receptors but not 5-HT(4) receptors as can be derived by using specific antagonists such as tropisetrone, GR113806 and ketanserine. Additional mechanisms (receptors) are involved since the combination of these three antagonists was not able to fully prevent the contractive effect of extract 36_U. The lipophilic extract 36_EB mainly containing cynarin, luteolin including its glycosides, and cholorogenic acid in contrast to extract 36_U had a relaxing effect which could hardly be washed out. It was diminishing a serotonin effect and was not modified by ACh or substance P. The peristaltic threshold, i.e. the distension necessary for inducing a pathophysiologically relevant propulsion activity, is one of the important features being correlated with IBS. The peristaltic threshold was decreased by both serotonin and extract U_36. From the data it can be derived that the extract 36_U may be useful in IBS combined with obstipation when gastrointestinal contraction is necessary, whereas 36_EB may be useful in IBS combined with diarrhea when gastrointestinal relaxation is desired. Especially interesting are the influence on the threshold. It would be interesting to know which effects are mediated via cynarin and luteolin or its glycosides.