Polyphenolic compounds can form insoluble complexes with macromolecules like proteins, reducing protein availability.

“this paper is talking about the inhibition of digestive enzymes by polyethylene compounds they say the ability of polyphenol compounds to form insoluble complexes with other macromolecules such as proteins has long been associated with The observed reduction in nutritive value resulting from their inclusion in animal diets okay it is concluded that the observed reduction in protein availability found in Vivo on consuming High tannin diets plant tannins plant defense chemicals cannot simply be explained by the formation of dietary protein tendon complexes and that the ability of polyphenolic compounds to inhibit digestive enzymes may be of Greater significance than realized previously”