Mixtures of catechins, (+)-catechin (C), (−)-epicatechin (EC), (−)-epigallocatechin (EGC) and (−)-epigallocatechin gallate (EGCG) have been analyzed by diffusion-ordered spectroscopy (DOSY) using liquid and high-resolution magic angle spinning (HR-MAS) NMR probes. Beta-cyclodextrin (β-CD) and bovin serum albumin (BSA), often used as ligands in affinity chromatography, were added to the mixture of catechins to mimic chromatographic conditions and modify the average mobility. The influence of the solvent, water, dimethyl sulfoxide, methanol, acetone and acetonitrile, was also investigated. The best separation of the components was achieved with β-CD in the liquid probe using a 15% CD3CN–85% D2O solution, and this was applied to the analysis of catechins from green tea extract. The parts of the catechin molecules having the closest contact to the BSA protein were also determined by saturation transfer difference (STD) NMR experiments.
通过使用液体和高分辨魔角旋转(HR-MAS)核磁共振探头,对
儿茶素混合物((+)-
儿茶素(C)、(−)-
表儿茶素(
EC)、(−)-表没食子
儿茶素(
EGC)和(−)-表
没食子儿茶素没食子酸酯(EGCG))进行了扩散有序谱(
DOSY)分析。为了模拟色谱条件并修改平均迁移率,向
儿茶素混合物中添加了常用于亲和色谱中的
配体β-
环糊精(β-CD)和
牛血清白蛋白(
BSA)。还研究了溶剂
水、
二甲基亚砜、
甲醇、
丙酮和
乙腈的影响。在液态探针中使用15% CD3CN–85% D2O溶液并在其中加入β-CD,获得了各组分的最佳分离效果,并将其应用于绿茶
提取物中
儿茶素的分析。通过饱和转移差异(STD)核磁共振实验还确定了与
BSA蛋白最接近接触的
儿茶素分子部分。