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

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• 作者：Andr茅 Sousa ; Vesselin Petrov ; Paula Ara煤jo ; Nuno Mateus ; Fernando Pina ; Victor de Freitas
• 刊名：The Journal of Physical Chemistry B
• 出版年：2013
• 出版时间：February 14, 2013
• 年：2013
• 卷：117
• 期：6
• 页码：1901-1910
• 全文大小：621K
• 年卷期：v.117,no.6(February 14, 2013)
• ISSN：1520-5207

文摘

Two oaklins guaiacylcatechinpyrylium (GCP) and syringylcatechinpyrylium (SCP) and a model compound deoxypeonidin (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鈥搕rans 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鈥搗is 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. Oaklin 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.