Introduction
Metabolization of medicinal plant extracts in the gastrointestinal tract may lead to the formation of new active compounds and could therefore be highly relevant for the explanation of the mode of action. STW-5 is a well-known liquid fixed 9-herb combination, which is effective in treating functional dyspepsia and irritable bowel syndrome (IBS) [1] . It was pre-digested by a static in-vitro digestion method and thereafter incubated with human gut bacteria to mimic human digestion and microbial fermentation in the gastrointestinal tract.
Method
Two concentrations of STW-5 were predigested in-vitro according to the InfoGest consensus method [2] . After protein precipitation, all samples were analyzed by UHPLC-HRMS and data were processed with Compound Discoverer 2.1 (Thermo Fisher Scientific). In order to assess metabolization during in-vitro digestion, UHPLC chromatograms of samples taken after simulated digestion were compared to respective STW-5 dilutions.
For bacterial fermentation, fecal samples of one donor were anaerobically incubated with InfoGest predigested STW-5 as well as with non-predigested STW-5 (two concentrations). Samples were taken after 30min, 4h and 24h of incubation, and analyzed by UHPLC-HRMS. After data processing, peak areas were compared to respective STW-5 dilutions incubated with PBS-buffer only.
Results
The majority of STW-5 main constituents were not significantly changed by in-vitro digestion. Microbial fermentation, however, led to fast metabolization of the major compounds detected in STW-5, such as flavonoids, caffeic acid derivatives, and triterpene glycosides.
References
[1] Kelber O, Bauer R, Kubelka W. Phytotherapy in Functional Gastrointestinal Disorders. Dig Dis 2017; 35 Suppl 1: 36–42
[2] Verhoeckx K, Cotter P, López-Expósito I, Kleiveland C, Lea T, Mackie A, Requena T, Swiatecka D, Wichers H. The Impact of Food Bioactives on Health. Cham: Springer International Publishing; 2015