Centro de Investigação em Química, Departamento de Química, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre, Portugal.
J Phys Chem B. 2012 Dec 6;116(48):14089-99. doi: 10.1021/jp307782y. Epub 2012 Nov 27.
The aim of this study is to investigate interactions possibly taking place in red wine between three flavanols (copigments, CP), i.e., two epimeric vinylcatechin dimers (CP1 and CP2) and catechin dimer B3 (CP3), and a specific pigment resulting from the condensation between the main grape anthocyanin malvidin 3-O-glucoside (oenin) and catechin, catechin-(4→8)-oenin. By comparison with our previous work on oenin itself, the influence of the catechin moiety of the anthocyanin in the binding is established. The thermodynamic parameters show that both vinylcatechin dimers exhibit a higher affinity for catechin-(4→8)-oenin, in comparison with proanthocyanidin B3, as previously observed with oenin. However, the corresponding binding constants are weaker, probably due to steric hindrance in the anthocyanin brought by the flavanol nucleus. Consequently, catechin-(4→8)-oenin should be much less stabilized by copigmentation in hydroalcoholic solution than oenin. Quantum mechanics and molecular dynamics simulations are also performed to interpret the binding data, to specify the relative arrangement of the pigment and copigment molecules within the complexes, and to interpret their absorption properties in the visible range.
本研究旨在探讨红葡萄酒中单宁（共色素）之间可能发生的相互作用，即两种差向 vinylcatechin 二聚体（CP1 和 CP2）和儿茶素二聚体 B3（CP3），以及由主要葡萄花色苷矢车菊素 3-O-葡萄糖苷（oenin）和儿茶素缩合而成的特定色素。与我们之前对 oenin 本身的研究相比，建立了花色苷儿茶素部分在结合中的影响。热力学参数表明，与原花青素 B3 相比，两种 vinylcatechin 二聚体对儿茶素-(4→8)-oenin 的亲和力更高，如之前观察到的 oenin 一样。然而，相应的结合常数较弱，可能是由于花色苷中 flavanol 核带来的空间位阻。因此，在水醇溶液中，儿茶素-(4→8)-oenin 与共色素的结合应远不如 oenin 稳定。量子力学和分子动力学模拟也用于解释结合数据，指定复合物中色素和共色素分子的相对排列，并解释它们在可见光范围内的吸收特性。
