Comparison of the inhibition of myeloperoxidase-catalyzed hypochlorite formation in vitro and in whole blood by different plant extracts contained in a phytopharmacon treating functional dyspepsia

Ethanolic extracts from nine medicinal plants are combined in Iberogast® (IG). This phytomedicine is successfully used in the treatment of gastrointestinal disorders. Functional gastrointestinal diseases such as non-ulcerous dyspepsia (NUD) are in many cases initiated by, or correlated to, inflammatory processes, where reactive oxygen species (ROS) play a crucial role. In this respect one prominent source of ROS are myeloperoxidase (MPO)-driven oxidation and chlorination reactions, assumed to be mainly responsible for tissue damage. In this study the contribution of the nine extracts to the overall performance of IG was compared with emphasis on MPO produced ROS. Concerning the influence on MPO-dependent chlorination reactions, it turned out that of the nine IG-components Iberis amara extract (IAE) exerted the highest activity. Furthermore, this can impressively be reproduced in an ex vivo experiment with whole blood, where neutrophilic leukocytes are activated by zymosan. Moreover, along with the extract of chamomile flowers, IAE counteracts the pro-oxidative properties of caraway, peppermint and celandine. As a consequence, IG was also efficiently inhibiting MPO-catalysed chlorinations. As shown by the addition of catalase, the pro-oxidative effects of caraway, peppermint and celandine are due to their content of hydrogen peroxide. The latter is probably an autoxidation product of certain monoterpenes in the essential oil part of these extracts. If one of the component extracts of IG is omitted, the antioxidant acitivity is reduced. Thus we conclude that all the single extracts combined in IG are of importance for the therapeutical effect, working in concert.