Physicochemical studies of new anthocyano-ellagitannin hybrid pigments: About the origin of the influence of oak C-glycosidic ellagitannins on wine color

Kinetic and thermodynamic UV/Vis and structural NMR spectroscopic investigations on the anthocyano-ellagitannin hybrid 1-deoxyvescalagin- (1β→8)-oenin revealed that its enhanced color stability relative to that of the red-colored pigment oenin and resulting bathochromism can be rationalized in terms of an intramolecular π-stacking between the grapederived oenin chromophore and the oak-derived vescalagin 4,6-hexahydroxydiphenoyl moiety. The results led us to suggest that this bathochromism-inducing molecular association could be the first ellagitannin-based molecular-level explanation of the red-to-purple color change that takes place during the aging of wine in oak barrels.