Introduction Human microbiota play a tremendous role in the interaction with natural products
ingested by humans, as these influence microbiota and even more, as these highly complex
products are metabolized by microbiota. This is of special relevance in case of natural
products in therapeutic use as herbal medicines.
Method For a key group of such products, the flavonoids, a study was conducted in male C57BL/6
mice, to assess the influence of a depletion of the microbiome on the psychotropic
effect of flavonoids [1]. A soluble combination herbal medicine used in GI diseases, STW 5, was examined
in the pharmacological model of DSS induced gut inflammation in Wistar rats [2] and in human fecal suspensions [3].
Results For the flavonoids kaempferol and quercetin, it was shown that these are prodrugs,
and their anxiolytic and antidepressant action depend on their microbial metabolism.
The improvement of DSS-induced gut inflammation by STW 5 was linked to a normalization
of the composition of the gut microbiome. In the fecal suspension model, a significant
influence on microbiota was shown, with a high interindividual variability of metabolism
of key constituents, e. g. glycyrrhizic acid to liquiritigenin and davidigenin.
Conclusion The action of natural products and their phytochemical constituents may to a large
extent depend on intestinal microbiota, and may to a large extend still be unexplored,
as recent review shows [4], in spite of the large number of studies available.
