Oliveira Joana, Azevedo Joana, Teixeira Natércia, Araújo Paula, de Freitas Victor, Basílio Nuno, Pina Fernando
LAQV-REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre, 687, 4169-007 Porto, Portugal.
LAQV-REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal.
J Agric Food Chem. 2021 Feb 3;69(4):1359-1367. doi: 10.1021/acs.jafc.0c05954. Epub 2021 Jan 20.
Anthocyanins co-pigmentation models with application on 1:1 complexes were revisited, and their limitations were critically commented. The flavylium multistate of species is dramatically simplified to a single acid-base equilibrium between flavylium cation and its conjugated base CB, equal to the sum of quinoidal base, hemiketal, and and -chalcones. Bearing this, a new equation that simultaneously allows calculation of the co-pigmentation constant with flavylium cation (+) and with its conjugated base CB () was deduced. This equation can be used at a fixed co-pigment concentration with pH as a variable or at fixed pH and co-pigment concentration variable. A global fitting of all data allows us to calculate both association constants with good accuracy. The model was applied to the co-pigmentation of malvidin-3-glucoside with caffeine and pentagalloyl glucose (PGG). Caffeine gives rise to complexes not only with flavylium cation + = 125 ± 7 M but also with CB with = 23 ± 3 M. PGG complexes exclusively with flavylium cation, + = 914 ± 10 M, and the possible interaction with quinoidal base is lower than the detection limits that the inherent experimental error permits.
重新审视了用于 1:1 配合物的花青素共色素模型，并对其局限性进行了批判性评论。物种的黄酮类多态性被极大地简化为黄酮阳离子与其共轭碱 CB 之间的单一酸碱平衡，CB 等于醌式碱、半缩酮以及和查耳酮的总和。基于此，推导了一个新的方程，该方程同时允许计算与黄酮阳离子（+）及其共轭碱 CB（）的共色素常数。此方程可在固定共色素浓度且以 pH 为变量的情况下使用，或以固定 pH 和共色素浓度为变量的情况下使用。对所有数据进行全局拟合使我们能够高精度地计算两个缔合常数。该模型应用于矢车菊素 -3- 葡萄糖苷与咖啡因和五倍子酰葡萄糖（PGG）的共色素作用。咖啡因不仅与黄酮阳离子形成配合物，其缔合常数 + = 125 ± 7 M，还与 CB 形成配合物，缔合常数 = 23 ± 3 M。PGG 仅与黄酮阳离子形成配合物，+ = 914 ± 10 M，并且与醌式碱的可能相互作用低于固有实验误差允许的检测限。
