Copigmentation

The anthocyanins are pH sensitive. Their color, in part, is deterrnined by the pH of the sap. Cyanin, for example, is red at pH 3, violet at 8, and blue at 11. However, there are other factors that affect the colors of the anthocyanins metallic salts, notably iron and aluminum, react with those anthocyanins containing vicinal hydroxy groups and produce highly colored complex compounds. Other factors are the colloidal condition of the cell sap and copigmentation (91). 

Eiro, M.J. and Heinonen, M., Anthocyanin color behavior and stability during storage effect of intermolecular copigmentation, J. Agric. Food Chem., 50, 7461, 2002. 

Attempts to stabilize anthocyanins by complex inclusion with a- and P-cyclo-dextrins failed on the contrary, a discoloration of anthocyanin solutions was observed.Thermodynamic and kinetic investigations demonstrated that inclusion and copigmentation had opposite effects. In the anthocyanins, the cw-chalcone colorless structure is the best species adapted to inclusion into the P-dextrin cavity, shifting the equilibrium toward colorless forms. "... 

Research into the copigmentation of anthocyanins started as early as 1913 when Willstatter and Everest determined the chemical structure of cyanidin 3-glucoside isolated from blue cornflowers and red roses, and attributed the color changes to different pH levels in cell saps. This theory, however, was questioned and in 1916, Willstatter and Zollinger,revising the previous work, proposed a new theory according to which the colors of the anthocyanins varied significantly by the effects... 

The color of malvidin 3-glucoside in aqueous solution can be stabilized by selfassociation or copigmentation with the di-chalcone form, according to the pH of the solution. ... 

The poor stability of anthocyanins with simple stractures can be overcome by intermolecular copigmentation reaction, that is, an association with different compounds, especially polyphenolic ones, stabilized by n-n intermolecular and hydrogen bonds. However, this complex dissociates at high temperatures. ... 

The magnitude of the copigmentation is influenced by pH value, pigment and copigment concentrations, chemical structure of anthocyanin, temperature, and ionic strength of the medium. As to the effect of the solvent, the important issue is the hydrogen-bonded molecular structure of the liquid water, not the polarity of the medium. ... 

The colors of muscadine grape juice and wine were enhanced by copigmentation with formonetin, biochanin A, and prunetin, the major isoflavonoids extracted from red clove leaves, at ratios of 1 2, 1 4, and 1 8. The 1 8 ratio representing the maximum amount of isoflavonoids used due to its limiting solubility yielded the maximum color enhancement when compared to standard solutions of anthocyanins, at 23 and 60°C. ... 

In 1967, Timberlake and Bridle proposed that copigmentation complex formation reactions between cyanidin and quercetin in aqueous buffered solutions took place between the colored forms of the flavylium cation (AH+) cyanidin at pH 3.0 and the quinoidal base (A) at pH 5.0. 

Studies of the stability and stabilization of anthocyanins are still required, based on the extreme importance of those pigments for food colors. Modem HPLC-MS equipment also allows us to easily follow the copigmentation reactions in detail, calculate their kinetic and thermodynamic parameters, identify the products formed during the reactions, and thus shed new light on the stability and stabilization of these pigments. Since anthocyanins play important roles as natural colorants for... 

Houbiers, C. et al.. Color stabilization of malvidin 3-glucoside self-aggregation on the of flavylium cation and copigmentation with the Z-chalcone form, J. Phys. Chem. B, 102, 3578, 1998. 

Dangles, O. et al.. Two very distinct types of anthocyanins complexation — copigmentation and inclusion. Tetrahedron Lett., 33, 5227, 1992. 

Bailoni, M.A., Bobbio, P.A., and Bobbio, P.O., Stability of the anthocyanins from Acalipha hispida and copigmentation effect, Acta AUmentaria, 28, 161, 1999. 

Dangles, O and Brouillard, R., Polyphenol interactions. The copigmentation case — thermodynamic data from temperature-variation and relaxation kinetics. Medium effect. Can. J. Chem.-Rev. Can. Chim., 70, 2174, 1992. 

Keepers, J.W. and James, T.L., A theoretical smdy of distance determinations from NMR two-dimensional nuclear Overhauser effect spectra, J. Mag. Resort, 57, 404, 1984. Kemp, W., Organic Spectroscopy, 3rd ed., W.H. Ereeman, New York, 1991. Figueiredo, P. et al., New aspects of anthocyanin complexation intramolecular copigmentation as a means for colour loss Phytochemistry, 41, 301, 1996. 

Oszmianski, J., Bakowska, A., and Piacente, S., Thermodynamic characteristics of copigmentation reaction of acylated anthocyanin isolated from blue flowers of Scutellaria baicalensis Georgi with copigments, J. Sci. Food Agric., 84, 1500, 2004. 

Figueiredo, P. et al., New aspects of anthocyanin complexation. Intramolecular copigmentation as a means for colour loss Phytochemistry, 41, 301, 1996. 

Nielsen, K.M. et al.. Antisense flavonol synthase alters copigmentation and flower color in lisianthus. Mol Breed., 9, 217, 2002. 

Aida, R. et al.. Copigmentation gives bluer flowers on transgenic torenia plants with the antisense dihydroflavonol-4-reductase gene. Plant Set, 160, 49, 2000. 

Mirabel, M. et al., Copigmentation in model wine solutions occurrence and relation to wine aging. 

Sarma, A.D. and Sharma, R., Anthocyanin-DNA copigmentation complex mutual protection against oxidative damage. Phytochemistry, 52, 1313, 1999. 

One of the best-established functions of anthocyanins is in the production of flower color and the provision of colors attractive to plant pollinators. Considerable effort has been made to give explanations for the color variations expressed by anthocyanins in plants. Various factors including concentration and nature of the anthocyanidin, anthocyanidin equilibrium forms, the extent of anthocyanin glycosidation and acylation, the nature and concentration of copigmentation, metal complexes, intra- and intermolecular association mechanisms, and influence of external factors like pH, salts, etc. have been found to have impact on anthocyanin colors. ... 

It is known that polyacylated anthocyanins are very stable in neutral or weakly acidic aqueous solutions, whereas simple anthocyanins are quickly decolorized by hydration at the 2-position of the anthocyanidin nucleus. The shift to blue colors and increased anthocyanin stability are in many cases simply achieved by intramolecular copigmentation involving... 

---