title: Thermodynamic and kinetic properties of a new myrtillin-vescalagin hybrid pigment.
abstract: During red wine maturation in contact with oak wood, C-glucosidic ellagitannins can react with anthocyanins, leading to new pigments. In this work the thermodynamic and kinetic constants of the network pH-dependent equilibrium of a new myrtillin (delphinidin 3-O-glucoside)-vescalagin hybrid pigment (1-deoxyvescalagin-(1β→8)-myrtillin) have been determined by UV-visible absorption and stopped-flow experiments and compared to those determined for myrtillin. The vescalagin substitution at the C-8' center of myrtillin entails important variations in the pigment behavior upon pH changes. The hybrid pigment showed lower pK'a and pKa values and a much higher value of Kt. As a consequence, at moderately acidic pH values (4 < pH < 6), the percentage of the hemiketal is much lower and the quinoidal base and the (E)-chalcone represent higher percentages relative to those for myrtillin. Therefore, the hybrid pigment can provide in slightly acidic or neutral solutions an exceptionally different color compared to that of myrtillin.
authors.affiliation: Grupo de Investigación en Polifenoles (GIP), Facultad de Farmacia, Universidad de Salamanca , E37007 Salamanca, Spain.
authors.forename: Ignacio
authors.initials: I
authors.lastname: García-Estévez
authors.forename: Raquel
authors.initials: R
authors.lastname: Gavara
authors.forename: Cristina
authors.initials: C
authors.lastname: Alcalde-Eon
authors.forename: Julián C
authors.initials: JC
authors.lastname: Rivas-Gonzalo
authors.forename: Stéphane
authors.initials: S
authors.lastname: Quideau
authors.forename: M Teresa
authors.initials: MT
authors.lastname: Escribano-Bailón
authors.forename: Fernando
authors.initials: F
authors.lastname: Pina
mesh_terms: D000872:Anthocyanins / Q000737:chemistry*; D003116:Color; D005960:Glucosides / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D047348:Hydrolyzable Tannins / Q000737:chemistry*; D007700:Kinetics; D010860:Pigments, Biological / Q000737:chemistry; D029963:Quercus; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics; D014920:Wine
chemical_list: D000872:Anthocyanins; D005960:Glucosides; D047348:Hydrolyzable Tannins; D010860:Pigments, Biological; C084709:vescalagin; C494120:delphinidin 3-O-glucopyranoside