Formation of anthocyanin-flavanol adducts in model solutions
Formation of anthocyanin-flavanol adducts in model solutions
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DOI：
10.1016/j.aca.2005.10.062
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发表时间：
2006-03-23
影响因子：
6.2
通讯作者：
Cheynier, V
中科院分区：
文献类型：
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作者：
Dueñas, M;Fulcrand, H;Cheynier, V
在pH 2.0-6.0的模拟溶液中，研究了锦葵素3-O-葡萄糖苷（Mv 3glc）与黄烷醇单体表儿茶素（-）的直接反应机理。直接反应与pH值密切相关。Mv 3glc和表儿茶素消失的速率随着pH值的增加而增加。表儿茶素对Mv 3glc的黄酸形式的亲核加成在所有pH值下都发生。在pH 2.0下，所得中间体黄烯产生具有A型键的无色Mv 3glc-表儿茶素加合物。在pH3.2 -6.0范围内，在正离子模式下，检测到两种新产物，其紫外-可见光谱特征为黄嘌呤离子，质量信号分别为m/z 633和453。假定这些产物是由中间体黄烯产生的Mv 3glc-表儿茶素的黄酸盐形式的降解产物。此外，在pH 4.0以上，表儿茶素的氧化促进了在m/z 78 - 1处检测到的新色素的形成，以正离子模式。这些离子归因于表儿茶素-Mv 3glc加合物，其通过将Mv 3glc添加到表儿茶素邻醌上形成，因为138 amu片段的损失表明黄烷醇B环和花青素苷A环之间的联苯或联苯醚键。(c)2005 Elsevier B. V.保留所有权利。
The mechanism of direct reactions between malvidin 3-O-glucoside (Mv3glc) and a flavanol monomer, (-)-epicatechin, was studied in model solutions in the pH range 2.0-6.0. The direct reactions are strongly related to pH. The rate of Mv3glc and epicatechin disappearance increased with pH. Nucleophilic addition of epicatechin onto the flavylium form of Mv3glc took place at all pH values. At pH 2.0, the resulting intermediate flavene yielded a colourless Mv3glc-epicatechin adduct with an A-type linkage. In the range pH 3.2-6.0, two new products with UV-vis spectra characteristic of those of xanthylium ions and mass signals at m/z 633 and 453, respectively, in the positive ion mode were detected. These products are postulated to be degradation products of the flavylium form of Mv3glc-epicatechin arising from the intermediate flavene. Moreover, above pH 4.0, oxidation of epicatechin promoted the formation of new pigments detected at m/z 78 1, in the positive ion mode. These ions were attributed to epicatechin-Mv3glc adducts formed by addition of Mv3glc onto the epicatechin o-quinone as the loss of a 138 amu fragment indicated a biphenyl or biphenyl-ether linkage between the flavanol B-ring and the anthocyanin A-ring. (c) 2005 Elsevier B.V. All rights reserved.