Self-association copigmentation

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. 

Miniati, E., Damiani, P, Mazza, G. (1992). Copigmentation and self-association of anthocyanins in food model systems. It. J. Food Sci., 4, 109-116. 

Copigmentation is usually classified in (a) intermolecular anthocyanin-anthocyanin self-association, (b) intermolecular anthocyanin-copigment (i.e., flavonoids, phenolic acids) association, (c) intermolecular anthocyanin-copigment-metal ion association or (d) intramolecular self-association of acylated anthocyanins. 

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). 

The color of anthocyanins is influenced not only by structural features (hydroxylation, methoxylation, glyco-sylation, acylation), but also by the pH of the solution in which they are present, copigmentation, metal complexa-tion and self-association. 

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