Synthesis and equilibrium multistate of new pyrano-3-deoxyanthocyanin-type pigments in aqueous solutions

• Type: Article in International Scientific Journal
• Date: 2017

Authors

Sousa, JLC (Author) Other; Gomes, V (Author) Other; Nuno Mateus (Author) FCUP; Pina, F (Author) Other; Victor de Freitas (Author) FCUP; Luis Cruz (Author) FCUP

Journal

Title: Tetrahedron

Vol. 73

Pages: 6021-6030

ISSN: 0040-4020

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 25 Citations

Scopus - 25 Citations

Other information

Authenticus ID: P-00N-4K8

DOI: 10.1016/j.tet.2017.08.051

Abstract (EN): 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).

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 10