725223-63-2Relevant academic research and scientific papers
Establishment of the chemical equilibria of different types of pyranoanthocyanins in aqueous solutions: Evidence for the formation of aggregation in pyranomalvidin-3- O -coumaroylglucoside-(+)-catechin
Cruz, Luís,Petrov, Vesselin,Teixeira, Natércia,Mateus, Nuno,Pina, Fernando,Freitas, Victor De
body text, p. 13232 - 13240 (2011/02/27)
The chemical equilibria of the pyranomalvidin-3-glucosides linked to (+)-catechin, (-)-epicatechin, and catechol moieties (and the respective coumaroylglucoside compounds) were established by means of UV-vis spectroscopy. The conjugated double bonds among pyranic rings C and D provide a higher electronic delocalization that prevents the nucleophilic attack of water at position 2. Consequently, besides flavylium cation (AH+), the bases A, A-, and A2- have been identified by increasing pH, and the respective acidity constants were determined by spectrophotometry. The formation of dimers at higher concentration was observed for pyranomalvidin-3-O-coumaroylglucoside-(+)-catechin, and the respective data treated by the exciton model suggests the formation of a dimer where the monomers form J-type aggregates with the dipolar moments in opposite directions and rotated by 174° at a distance of 5.2 A? (from the center).
