Charge-Transfer Complexation as a General Phenomenon in the Copigmentation of Anthocyanins

Color intensification of anthocyanin solutions in the presence of natural polyphenols (copigmentation) is re-interpreted in terms of charge transfer from the copigment to the anthocyanin. Flavylium cations are shown to be excellent electron acceptors (E red ≈ −0.3 V vs SCE). It is also demonstrated,...

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Published in:The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2005-08, Vol.109 (32), p.7329-7338
Main Authors: Ferreira da Silva, Palmira, Lima, João C, Freitas, Adilson A, Shimizu, Karina, Maçanita, Antonio L, Quina, Frank H
Format: Article
Language:English
Subjects:
Anthocyanins - chemistry
Coumaric Acids - chemistry
Electrons
Flavonoids - chemistry
Hydrogen-Ion Concentration
Ions - chemistry
Models, Molecular
Molecular Structure
Phenols - chemistry
Polyphenols
Solutions
Spectrum Analysis
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Summary:Color intensification of anthocyanin solutions in the presence of natural polyphenols (copigmentation) is re-interpreted in terms of charge transfer from the copigment to the anthocyanin. Flavylium cations are shown to be excellent electron acceptors (E red ≈ −0.3 V vs SCE). It is also demonstrated, for a large series of anthocyanin−copigment pairs, that the standard Gibbs free energy of complex formation decreases linearly with EAAnthoc − IPCop, the difference between the electron affinity of the anthocyanin, EAAnthoc, and the ionization potential of the copigment, IPCop. Based on this correlation, copigmentation strengths of potential candidates for copigments can be predicted.
ISSN:1089-5639
1520-5215
DOI:10.1021/jp052106s