24 Condensed tannins: structure, activity and characterization

Abstract

Abstract As a class of plant polyphenolic compounds contained in some forages [i.e., sainfoin (Onobrychis viciifolia Scop.), big trefoil (Lotus pedunculatus Cav.), birdsfoot trefoil (Lotus corniculatus L.)], condensed tannins (CTs) exhibit a variety of biological effects on ruminants. The potential positive impact of CTs on the agricultural industry stems from their ability to modulate proteolysis during forage conservation and ruminal digestion, to prevent bloat, to reduce intestinal parasite burdens, and to abate methane and ammonia emissions from ruminants. How CTs exert these effects on ruminants focuses on the interaction of CTs with proteins. The structure-activity relationship in CT–protein interaction is not well understood but is known to be dependent on the structure and properties of both the CT and the protein. The objectives of this presentation are fivefold. First, examples of the structural diversity of CTs will be provided to enable the audience members to appreciate that not all CTs are the same. Second, examples of how CTs structural diversity affects their interaction with the protein, which in turn, dictates the biological response from the animal will be discussed. Third, the presentation will outline hurdles in obtaining highly pure and well-characterized CTs from natural sources for use in CT structural analysis and in vitro experiments. This will be followed by brief descriptions of improved and emerging techniques for CT analysis and, finally, the presentation concludes with questions to address in future investigations and a list of recommendations for CT researchers to follow.