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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Establishment of the Chemical Equilibria of Different Types of Pyranoanthocyanins in Aqueous Solutions: Evidence for the Formation of Aggregation in Pyranomalvidin-3-O-coumaroylglucoside-(+)-catechin
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Establishment of the Chemical Equilibria of Different Types of Pyranoanthocyanins in Aqueous Solutions: Evidence for the Formation of Aggregation in Pyranomalvidin-3-O-coumaroylglucoside-(+)-catechin

机译：在水溶液中建立不同类型的吡喃花色素的化学平衡的建立：吡喃马维丁-3-O-香豆酰葡萄糖苷-（+）-儿茶素中形成聚集的证据

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The chemical equilibria of the pyranomalvidin-3-glucosides linked to (+)-catechin, (-)-epicatechin. and catechol moieties (and the respective coumaroylglucoside compounds) were established by means of UV-vis spectroscopy. The conjugated double bonds among pyranic rings C and D provide a higher electronic delocalization that prevents the nucleophilic attack of water at position 2. Consequently, besides flavylium cation (AH~+). the bases A, A~-, and A~(2-) have been identified by increasing pH. and the respective acidity constants were determined by spectrophotometry. The formation of dimers at higher concentration was observed for pyranomalvidin-3-O-coumaroylglucoside-(+)-catechin, and the respective data treated by the exciton model suggests the formation of a dimer where the monomers form J-type aggregates with the dipolar moments in opposite directions and rotated by 174° at a distance of 5.2 A (from the center).
机译：与（+）-儿茶素，（-）-表儿茶素相连的吡喃马维丁-3-葡萄糖苷的化学平衡。通过紫外-可见光谱法确定了邻苯二酚和邻苯二酚部分（以及各自的香豆酰基葡糖苷化合物）。吡喃环C和D之间的共轭双键提供了更高的电子离域作用，可防止水在位置2发生亲核攻击。因此，除黄酮阳离子（AH〜+）外。通过增加pH值可以确定碱基A，A〜-和A〜（2-）。用分光光度法测定各自的酸度常数。对于吡喃马维菌素-3-O-香豆酰葡糖苷-（+）-儿茶素，观察到较高浓度的二聚体形成，并且通过激子模型处理的各个数据表明形成了二聚体，其中单体与偶极形成J型聚集体沿相反方向转动力矩，并以5.2 A（距中心）的距离旋转174°。

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