Different effects of the herbal combination STW 5 in small and large intestine of rats

Herbal medicinal products belong to the most successful treatment options in irritable bowel syndrome (IBS), a functional disorder of the gastrointestinal tract which is still not completely understood in its pathogenesis. The aetiology includes disturbed mechanical transport, caused by hyper- or hypomotility of intestinal smooth muscles. For the herbal combination STW 5 (Iberogast^®), the influence on spontaneous and induced contractions of ring preparations from murine jejunum, ileum and colon was determined in an organ bath device.

The results show that small intestine shows very regular spontaneous contractions under in vitro conditions (amplitude 1.8±0.4 mN, frequency 19.8±3.5 per min) which are inhibited in dose dependent manner by STW 5 and its constituent extracts. (e.g. 50% inhibition by STW 5 in a dilution of 10µL/mL physiological solution, 90% inhibition by peppermint extract). The spontaneous activity of large intestine is less pronounced and reveals stronger contractions but a very low frequency. With these specimens the inhibitory effect of STW 5 is less pronounced and corresponds to 10–25% inhibition at the same given concentration. When contractions were stimulated by acetylcholine (10µM) or by KCl-induced depolarisation (90 mM KCl) the inhibitory effects of STW 5 were similar in both types of intestine.

It can be concluded, that STW 5 has stronger effects in the more proximal parts of the intestine rather than in distal ones under in vitro conditions. However, spasmolysis after stimulated contraction can be achieved in small and large intestine.

Keywords: Irritable bowel syndrome, functional dyspepsia, Iberis amara, Peppermint, Mentha piperita, intestine