Stability of polyphenolics in a model digestive system

Understanding the chemical stability of tannins (polyphenolics) in the gastrointestinal tract is critical to understanding their biological activities and fate. We examined the stability of pentagalloyl glucose (PGG) and epigallocatechin gallate, (EGCG) in aqueous solutions under conditions simulating the mammalian GI tract. We evaluated tannin stability by HPLC, looking for both losses and conversion to other simpler phenolics. Both compounds were stable for over 80 hours at room temperature with ambient atmosphere. In the simulated gastric system (pH 2, pepsin, with or without added foods) both compounds were stable. At intestinal pH (7.4) the tannins decomposed leaving only 10% of the starting material. Addition of digestive components (pancreatin, lipase, bile) and/or food (homogenized infant food or dry breakfast cereal) stabilized EGCG slightly, increasing recovery to about 20% of the starting material. Addition of food provided the same slight stabilization of PGG, but addition of the digestive components with or without the food significantly stabilize the PGG, so that up to 60% of the starting material was recovered intact. The data suggest that different polyphenolics will have very different GI fates, and that interactions between the polyphenolic and the components of the gastrointestinal milieu may be important determinants of fate and bioavailability.

Acknowledgements: Financial support was provided by Agricultural Research Services Specific Cooperative Agreement Number 58–1932–6-634 with Miami University.