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

• Type: Article in International Scientific Journal
• Date: 2010

Authors

Luis Cruz (Author) Other; Petrov, V (Author) Other; Teixeira, N (Author) Other; Nuno Mateus (Author) FCUP; Pina, F (Author) Other; Victor de Freitas (Author) FCUP

Journal

Title: Journal of Physical Chemistry B

Vol. 114 No. 1

Pages: 13232-13240

ISSN: 1520-6106

Publisher: American Chemical Society

Indexing

ISI Web of Knowledge - 45 Citations

Scopus - 46 Citations

Scientific classification

FOS: Engineering and technology > Chemical engineering

CORDIS: Physical sciences > Chemistry > Analytical chemistry > Spectrochemistry ; Physical sciences > Chemistry > Organic chemistry

Other information

Authenticus ID: P-003-1TX

DOI: 10.1021/jp1045673

Abstract (EN): 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 A(2-) 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 for-nation of a chiller where the monomers form J-type aggregates with the dipolar moments in opposite directions and rotated by 174 degrees at a distance of 5.2 angstrom (from the center).

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 9