Assessing the role of the gut microbiome for the mode of action of the fixed herbal combination STW-5

STW-5 is a fixed combination of nine medicinal plants, that is used for the treatment of functional gastrointestinal disorders.

An in-vitro platform was used to simulate the digestion of STW-5 in the upper intestinal tract, followed by microbial fermentation with human faecal samples to assess its possible impact on human gut microbiome. STW-5 was predigested by means of the static in-vitro digestion model InfoGest [1] to mimic the conditions in the upper gastrointestinal tract. Thereafter, the predigested STW-5 was incubated with 10% stool suspension obtained from 10 healthy donors under anoxic conditions at 37°C (physiological conditions). Samples were drawn after 30min, 4h and 24h of incubation, in order to investigate the changes of the metabolic profiles caused by gut microbial metabolization of STW-5 by UHPLC-HRMS metabolomics, and to detect shifts in the microbial community composition occurring upon incubation with STW-5 by Illumina 16S-rDNA Next Generation Sequencing [2].

In-vitro predigestion did not significantly alter the composition of STW-5. While phenolic constituents like liquiritin were completely degraded after 30min by the human stool slurries, residual amounts of the triterpene glycoside glycyrrhizic acid (2-13% of initial levels) were still detectable in 4 of 10 samples after 24h. Metabolites like davidigenin became detectable after 30min or 4h and decreased again in 7 samples after 24h, indicating their further metabolization. The microbiome composition of the 10 samples was very heterogenous, indicating that microbiome shifts caused by STW-5 depend on the individual donor’s gut microbiome.

• References

• 1 Minekus M, Alminger M, Alvito P, Ballance S, Bohn T, Bourlieu C. et al. A standardised static in vitro digestion method suitable for food - an international consensus. Food Funct 2014; 5: 1113-1124.
• 2 Pferschy-Wenzig EM, Koskinen K, Moissl-Eichinger C, Bauer R. A Combined LC-MS Metabolomics- and 16S rRNA Sequencing Platform to Assess Interactions between Herbal Medicinal Products and Human Gut Bacteriain Vitro: A Pilot Study on Willow Bark Extract. Front Pharmacol 2017; 8: 893.