Thermodynamics, Kinetics, and Photochromism of Oaklins: A Recent Family of Deoxyanthocyanidins

• Type: Article in International Scientific Journal
• Date: 2013

Authors

Andre Sousa (Author) Other; Vesselin Petrov (Author) Other; Paula Araujo (Author) Other; Nuno Mateus (Author) FCUP; Fernando Pina (Author) Other; Victor de Freitas (Author) FCUP

Journal

Title: Journal of Physical Chemistry B

Vol. 117

Pages: 1901-1910

ISSN: 1520-6106

Publisher: American Chemical Society

Indexing

ISI Web of Knowledge - 11 Citations

Scopus - 11 Citations

Scientific classification

FOS: Natural sciences > Chemical sciences

Other information

Authenticus ID: P-002-0GS

DOI: 10.1021/jp3110216

Abstract (EN): Two oaldins guaiacylcatechinpyrylium (GCP) and syringylcatechinpyrylium (SCP) and a model compound deoxy-peonidin (DOP) were synthesized, and the rate and equilibrium constants of the respective pH dependent network of chemical reactions were calculated. In contrast to anthocyanins, the three compounds possess a small cis-trans isomerization barrier and hence the rate of the trans-chalcone formation follows a bell-shaped curve as a function of pH. The three compounds exhibit photochromism obtained by irradiation of the trans-chalcone, which, depending on pH, leads to the colored species flavylium cation and quinoidal base. The flash photolysis together with pH jumps followed by UV-vis absorption and stopped flow is a very useful tool to achieve the rate and equilibrium constants of the network of chemical reactions followed by these molecules. Oak lin compounds which are formed in wine aged in oak barrels present physical-chemical properties more similar to simpler deoxyanthocyanidins rather than anthocyanins and may play a significant role in color changes observed in wine aging. Given their higher stability, they may be regarded as potential food colorants.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 10