The efficacy of combined plant extracts of STW 5 on intestinal neurotransmission and motility in an experimental animal model

The phytomedicine STW 5 (Iberogast®) is a fixed combination of the fresh plant fluid extract of Iberis amara totalis and the fluid extracts of eight herbal drugs, Angelica root, Matricaria flower, Caraway fruit, St. Mary's thistle fruit, Balm leaves, Peppermint leaves, Greater Celandine herb and Liquorice root. Its clinical efficacy in functional gastrointestinal diseases was shown by several randomized controlled clinical studies and more than 50 years of clinical experience. The aim of this study was to clarify, whether combined plant extracts of STW 5 act on contractions elicited after electrical field stimulation (EFS) in the small intestine of mice in vitro.

In organ bath experiments contractions were elicited in the small intestine of mice using electrical field stimulation EFS. Single components of STW 5 were tested alone in dilutions of 1:1000, 1:500 and 1:100 and in presence of Iberis amara in a dilution of 1:500 (20 min. preincubation).

Iberis amara alone had not significant effect in 1:500 dilution on EFS-induced contractions in murine small intestine. The combinations of Iberis amara with Angelica roots, Caraway fruits or Greater Celandine herbs was more effective in reducing EFS contractions compared to the single extracts alone. No significant differences were seen in combination with Peppermint leaves, Matricaria flower, St. Mary's thistle fruits, or Lemon balm leaves. Liquorice roots increased EFS contractions alone (n.s.), the combination with Iberis amara significantly reduced this effect.

The combination of different extracts of STW 5 with Iberis amara shows potentiating effects on some compounds (Dual Principle of Action). Iberis amara presence seems to be crucial for the overall effect of STW 5.