Abstract

It was shown that the differential spectrophotometric method for the determination of monomeric anthocyanins (in a mixture with polymeric ones) is unsuitable for measurements of anthocyanins acylated by substituted cinnamic acids. This is explained by a competition between the reaction of the nucleophilic addition of a water molecule (with the release of H⁺) to flavylium ions with the formation of a noncolored pseudo-base (A) and the reaction of the deprotonation of flavylium ions with the formation of quinonoid structures (B), which are also colored with a certain bathochromic shift of the absorption maximum. It was proposed to estimate the applicability of the differential spectrophotometric method by comparing differences between the spectra recorded at different pH (1, 2, 3, 4, and 4.5). The method is applicable at the prevalence of route A, when the specified differences between the spectra are undistinguishable taking into account scaling. The method is inapplicable for the main route B, when spectral differences can be distinguished. In the second case, a simplified method for the determination of anthocyanins without the account of polymeric anthocyanins is justified.

中文翻译：

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分光光度法测定单体花色苷的特征

摘要

结果表明，差示分光光度法测定单体花色苷（与聚合花色苷的混合物）不适用于测定被肉桂酸酰化的花色苷。这可以通过水分子的亲核加成反应（与H ⁺的释放）之间的竞争来解释。）到黄酮离子，形成无色假碱（A），以及黄酮离子去质子化与形成醌型结构（B）的反应，后者也被着色，并具有最大吸收的一定的红移。建议通过比较在不同pH（1、2、3、4和4.5）下记录的光谱之间的差异来估计差示分光光度法的适用性。该方法适用于路线A的普遍性，考虑到缩放比例后光谱之间的指定差异无法区分。当可以区分光谱差异时，该方法不适用于主要路线B。在第二种情况下，无需考虑聚合物花色苷的测定，就可以简化测定花色苷的方法。