Intermolecular copigmentation

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

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. ... 

It involves, on one hand an anthocyanin under its flavylium or quinonoidal base form, and on the other hand another planar hydrophobic structure that can be another anthocyanin unit (self-association), or another colorless species (copigment), covalently bound (intramolecular copigmentation) or not (intermolecular copigmentation) to the anthocyanin pigment. 

MALIEN-AUBERT c, DANGLES o and AMIOT M J (2001), Color Stability of commercial anthocyanin-based extracts in relation to the phenolic composition. Protective effects by into and intermolecular copigmentation , J Agric Food Chem, 49, 170-176. 

Malien-Aubert, C., Dangles, O., Amiot, M. J. Color Stability of Commercial Anthocyanin-Based Extracts in Relation to the Phenolic Composition. Protective Effects by Intra- and Intermolecular Copigmentation. J. Agric. Food Chem. 49, 170-176, 2001. 

Fig. 57.12 Schematic representation of the intermolecular copigmentation between anthocyanins and flavonoids. (—), anthocyanin (—), flavonoids [170]...

At the plants pH values (3-7), anthocyanins are mostly present as colorless structures. But a stabilizing mechanism takes place. Such effects are provided by complexation of the color form with other species present in the solution, which can be either an identical anthocyanin molecule (self-association), one of its aromatic acyl groups substituents (intramolecular copigmentation) or another molecule (intermolecular copigmentation). 

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