Sunflower extraction meal, a co-product from sunflower oil production, is an economically interesting source of protein. During alkaline extraction of proteins, the presence of chlorogenic acid in the meal gives rise to the formation of o-quinones. Reactions with nucleophiles present in proteins can lead to green discoloration. Although such reactions have been known for a long time, there is a lack of information on the chemical nature of the reaction products. The work described in this thesis sought to understand the underlying interaction mechanism. The resulting green interaction products were tentatively identified as trihydroxy benzacridine derivatives. Special attention was given to the potential use of polyphenol-protein complexes in animal nutrition. It was shown that a targeted alkaline treatment of naturally occurring compounds in feedstuffs might be a promising approach to provide ruminant feed with improved intestinal digestibility values.