Anti-inflammatory effect of STW 5, STW 6 and isolated extracts on the rat small intestine

STW 5 (Iberogast®), an established gastrointestinal phytotherapeutic medication is a combination of nine plant extracts. The main ingredient, STW 6 (Iberis amara), stimulates motor processes of the gut, acts anti-inflammatory and protects the mucosa. In order to characterize further effects the fixed combination STW 5 and its main constituent herbal component STW 6 as well as some isolated extracts were tested in an in vitro inflammation model on rat small intestine. The inflammation was induced by intraluminal instillation of 2,4,6-trinitrobenzolsulfonic acid (TNBS, 0.01M) in the isolated small intestinal preparation for 30min. STW 6 solved in water was stepwise macerated by hexane (HEX), chloroform (CHCl₃) and ethylacetate (EA). These extracts were analysed qualitatively by thin layer chromatography und quantitatively by HPLC. Constituents of the CHCl₃ and EA extract were e.g. cucurbitacins, of the residual aqueous fraction (rAF) e.g. glucosinolates. Flavonoids were identified in CHCl₃, EA and rAF. The HEX extract was almost free of constituents. Preincubation of the preparations with TNBS resulted in an inhibition of the ACh-induced contraction. Preincubation of STW 5 (64–512µg/ml) or STW 6 (3–24µg/ml) together with TNBS concentration-dependently prevented this effect. Using the same procedure the CHCl₃ and EA extracts also prevented the TNBS-induced inhibition of the ACh contraction. The rAF was without effect.

In conclusion, our experiments confirmed the anti-inflammatory effect of STW 5 and STW 6 and shows that constituents within the extracts macerated CHCl₃ and EA may be the anti-inflammatory acting agents within STW 6. These constituents appear to be involved in the multi-target actions of STW 5 (Iberogast®).