Interaction between cyanidin 3-glucoside and Cu(II) ions

The interaction between cyanidin 3-glucoside (Cy 3-glc) and Cu(II) in a binary solvent (methanol water, 1: 1, (v/v)) and in a phosphate buffer was studied. It is demonstrated that Cy 3-glc and Cu(II) ions form a complex that is manifested by appearance of a new absorption band. In the complex, the reduction of Cu(II)-Cu(I) and oxidation of Cy 3-glc takes place. The association constant of the complex formation was calculated using the Rose-Drago method. The complex stoichiometry in the binary solvent was 1: 1, and the association constant was K = (28,600 +/- 2600) M-1. Interaction of Cy 3-glc and Cu(II) ions has two stages fast and slow. The kinetics of these processes has been investigated. Thermodynamic data for the fast process: enthalpy (Delta H*) and entropy (Delta E*) of activation, were calculated. (C) 2007 Elsevier Ltd. All rights reserved.