Polyphenolic compounds are common constituents of human and animal diets and undergo extensive metabolism
by the gut microbiota before entering circulation. In order to compare the transformations of polyphenols
from yerba mate, rosemary, and green tea extracts in the gastrointestinal tract, simulated gastrointestinal
digestion coupled with colonic fermentation were used. For enhancing the comparative character of the investigation,
colonic fermentation was performed with human, pig and rat intestinal microbiota. Chemical analysis
was performed using a HPLC system coupled to a diode-array detector and mass spectrometer. Gastrointestinal
digestion diminished the total amount of phenolics in the rosemary and green tea extracts by 27.5 and 59.2 %,
respectively. These reductions occurred mainly at the expense of the major constituents of these extracts, namely
rosmarinic acid (-45.7 %) and epigalocatechin gallate (-60.6 %). The yerba mate extract was practically not
affected in terms of total phenolics, but several conversions and isomerizations occurred (e.g., 30 % of trans-3-Ocaffeoylquinic
acid was converted into the cis form). The polyphenolics of the yerba mate extract were also the
least decomposed by the microbiota of all three species, especially in the case of the human one (-10.8 %). In
contrast, the human microbiota transformed the polyphenolics of the rosemary and green extracts by 95.9 and
88.2 %, respectively. The yerba mate-extract had its contents in cis 3-O-caffeoylquinic acid diminished by 78 %
by the human microbiota relative to the gastrointestinal digestion, but the content of 5-O-caffeoylquinic acid
(also a chlorogenic acid), was increased by 22.2 %. The latter phenomenon did not occur with the rat and pig
microbiota. The pronounced interspecies differences indicate the need for considerable caution when translating
the results of experiments on the effects of polyphenolics performed in rats, or even pigs, to humans.
