The six most common 3-glucoside anthocyanins, pelargonidin-3-glucoside, peonidin-3-glucoside, delphinidin-3-glucoside, malvidin-3-glucoside, cyanidin-3-glucoside and petunidin-3-glucoside were studied in great detail by NMR, UV-vis absorption and stopped flow. For each anthocyanin, the thermodynamic and kinetic constants of the network of chemical reactions were calculated at different anthocyanin concentration, from 6 x 10(-6) M up to 8 x 10(-4) M; an increasing of the flavylium cation acidity constant to give quinoidal base and a decreasing of the flavylium cation hydration constant to give hemiketal were observed by increasing the anthocyanin concentration. These effects are attributed to the self-aggregation of the flavylium cation and quinoidal base, which is stronger in the last case. The UV-vis and H-1 NMR spectral variations resulting from the increasing of the anthocyanin concentration were discussed in terms of two aggregation models; monomer-dimer and isodesmic, the last one considering the formation of higher order aggregates possessing the same aggregation constant of the dimer. The self-aggregation constant of flavylium cation at pH = 1.0, calculated by both models increases by increasing the number of methoxy (-OCH3) or hydroxy (-OH) substituents following the order: myrtillin (2 -OH), oenin (2 -OCH3), 3-OGI-petunidin (1 -OH, 1 -OCH3), kuromanin (1 -OH), 3-OGI-peonidin (1 -OCH3) and callistephin (none). Evidence for flavylium aggregates possessing a shape between J and H was achieved, as well as for the formation of higher order aggregates. (C) 2012 Elsevier Ltd. All rights reserved.
ISI Document Delivery No.: 028KLTimes Cited: 3
Cited Reference Count: 36
Leydet, Yoann Gavara, Raquel Petrov, Vesselin Diniz, Ana M. Jorge Parola, A. Lima, Joao C. Pina, Fernando
Parola, A. Jorge/F-4048-2010; Gavara, Raquel/C-6669-2013; Diniz, Ana /C-6705-2013; Pina, Fernando/C-8161-2011; Caparica, cqfb_staff/H-2611-2013; REQUIMTE, AL/H-9106-2013; Chaves, Pedro/K-1288-2013; Lima, Joao/F-3658-2010
Parola, A. Jorge/0000-0002-1333-9076; Lima, Joao/0000-0003-0528-1967
Fundacao para a Ciencia e Tecnologia, through National NMR Network [PTDC/QUI-QUI/117996/2010, SFRH/BPD/44230/2008, SFRH/BPD/44639/2008, SFRH/BPD/18214/2004, SFRH/BD/48226/2008]
This work was supported by Fundacao para a Ciencia e Tecnologia, through National NMR Network, projects PTDC/QUI-QUI/117996/2010, SFRH/BPD/44230/2008 (YL), SFRH/BPD/44639/2008 (RG), SFRH/BPD/18214/2004 (VP), SFRH/BD/48226/2008 (AD).
Pergamon-elsevier science ltd
Oxford