Interaction of flavanoids with peptides and proteins and conformations of dimeric flavanoids in solution.

Although the physiological roles of tannins and related polyphenols in plants have not yet been clarified, their ability to form complexes with proteins or related biopolymers has been correlated with some protection of the plants from predators such as animals, insects, and microbes.’ Similarly, commercial uses of tannins, especially in the leather and brewing industries, are also based on their binding with proteins.2 Pharmacological properties of tannins have been investigated based on recent advances in the structural study of tannins in medicinal plants, and various actions of tannins including antitumor and antiviral effects have been revealed.3 These effects are attributed to interactions with certain biomolecules in organisms, too. Most of these effects are dependent on the chemical structures or molecular shapes of tannins.3 Therefore, clarification of the molecular conformations of tannins and related polyphenols is requisite to understanding the process of molecular interaction of tannins with the biomolecules. Here we summarize our reports on the conformational analyses of dimeric flavanoids related to condensed tannins and interaction of these flavanoids with peptides. Because molecular