Synthesis and equilibrium multistate of new pyrano-3-deoxyanthocyanin-type pigments in aqueous solutions
authors Sousa, JLC; Gomes, V; Mateus, N; Pina, F; de Freitas, V; Cruz, L
nationality International
journal TETRAHEDRON
author keywords Pyrano-3-deoxyanthocyanins; Dyes; Chemical equilibria; UV-Vis spectroscopy; pK(a)
keywords ANTHOCYANIN-DERIVED PIGMENTS; WINE PIGMENTS; COLOR; PH; PYRANOANTHOCYANINS; CHEMISTRY; SYSTEM; FORMS; PHOTOCHROMISM; METABOLITE
abstract Pyrano-flavylium compounds are flavylium derivatives with occurrence in processed foodstuffs such as wine and red fruit juices. In this work, the chemical equilibria of "bio-inspired" pyrano-3deoxyanthocyanin dyes (4-8), presenting different substituent groups in D ring (10-methyl, 10-catechol, 10-dimethylaminophenyl, 10-carboxy) as well as in B ring (3',4'-dihydroxy, 4'-carboxy), were studied for the first time in aqueous solutions by UV-Vis spectroscopy. The presence of a methyl group at C-10 (pigment 4) seems to stabilize the flavylium cation (AH(+)) shifting the deprotonation of 7-OH to a higher pK(a1) (pK(a1) = 5.0 0.1). On the other hand, the quinoidal bases (A, A(-)) were more stabilized for the pigments which undergo the first acid-base equilibrium at C-10 substituent, as could be observed by the pICa2 constants (pK(a2) = 8.4 +/- 0.1 and pK(a2) = 8.1 +/- 0.1, pigments 6 and 8, respectively). (C) 2017 Elsevier Ltd. All rights reserved.
publisher PERGAMON-ELSEVIER SCIENCE LTD
issn 0040-4020
year published 2017
volume 73
issue 41
beginning page 6021
ending page 6030
digital object identifier (doi) 10.1016/j.tet.2017.08.051
web of science category Chemistry, Organic
subject category Chemistry
unique article identifier WOS:000412957800006
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journal analysis (jcr 2017):
journal impact factor 2.377
5 year journal impact factor 2.255
category normalized journal impact factor percentile 60.526
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