Effect of ferrous and ferric ions on copigmentation in model solutions

Sándor Kunsági-Máté, Erika Ortmann, László Kollár, Kornélia Szabó, Martin Pour Nikfardjam

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12 Citations (Scopus)


The thermodynamics of the molecular association process between malvidin-3-O-glucoside and ellagic acid (so-called "copigmentation") was studied in model wine solutions in the presence and absence, respectively, of ferrous and ferric ions. The Gibbs free energy, enthalpy, and entropy values of the complexation process were determined by means of a spectrofluorometric method. A combination of the Job's method with the van't Hoff theory was used for data evaluation. The results show the generally exothermic character of the process. The free enthalpy changes obtained during formation of malvidin-3-O-glucoside-ellagic acid complexes increase from -17.8 kJ/mol to -40.5 kJ/mol in the presence of Fe(II) ions. The increased free enthalpy is a consequence of the drastic reduction of entropy change due to the slight "swinging" movement of the interacting malvidin and ellagic acid molecules in the complexes stabilized by the ferrous ions. These results are also supported by the findings of other authors stating that iron ions play an important role in the stabilization of color in the plant kingdom and various plant products.

Original languageEnglish
Pages (from-to)471-474
Number of pages4
JournalJournal of Molecular Structure
Issue number1-3
Publication statusPublished - Nov 26 2008


  • Anthocyanin
  • Copigmentation
  • Ellagic acid
  • Fluorometry
  • Iron

ASJC Scopus subject areas

  • Analytical Chemistry
  • Spectroscopy
  • Organic Chemistry
  • Inorganic Chemistry

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