Methods and Application of Food Composition Laboratory, U.S. Department of Agriculture, Agricultural Research Service, Beltsville Human Nutrition Research Center, Beltsville, MD, 20705, USA.
Department of Chemistry & Biochemistry, College of Arts and Sciences, Ohio University, Athens, OH, 45701, USA.
Anal Bioanal Chem. 2020 Jul;412(18):4343-4352. doi: 10.1007/s00216-020-02669-7. Epub 2020 May 5.
The thiolysis of B-type proanthocyanidins in cocoa by cysteamine was evaluated and optimized for its application in cocoa proanthocyanidin quantification. Four thiolysis products consisting of epicatechin, catechin, and their thioethers formed with cysteamine were separated and characterized by reversed-phase UPLC with photo diode array (PDA) detection and high-resolution mass spectrometry (HRMS). A thiolysis time of 20 min under 60 °C temperature was determined as the optimal condition for cocoa proanthocyanidin depolymerization. The optimized thiolysis condition was applied to four cocoa bean samples for proanthocyanidin quantification, using commercially available procyanidin B2 dimer as a reference standard. Satisfactory linearity and quantification and detection limits were achieved for the calibration curves, and proanthocyanidin contents determined by thiolysis were found to be higher than those determined by a published method based on normal-phase HPLC with fluorescence detection. Results in this study suggest promising application potential of cysteamine as an odorless thiolysis agent in routine quantitative analysis of B-type proanthocyanidins. Graphical abstract.
半胱胺对可可中 B 型原花青素的巯基裂解作用进行了评估和优化，以应用于可可原花青素的定量分析。通过反相高效液相色谱-光电二极管阵列（PDA）检测和高分辨质谱（HRMS），分离并鉴定了由半胱胺与表儿茶素、儿茶素及其硫醚形成的 4 种巯基裂解产物。确定在 60°C 温度下 20 分钟的巯基裂解时间为可可原花青素解聚的最佳条件。将优化的巯基裂解条件应用于 4 种可可豆样品中原花青素的定量分析，以市售的原花青素 B2 二聚体为参考标准。校准曲线的线性、定量和检测限均令人满意，通过巯基裂解法测定的原花青素含量高于基于荧光检测的正相高效液相色谱法的测定值。本研究结果表明，半胱胺作为一种无味的巯基裂解试剂，在 B 型原花青素的常规定量分析中具有潜在的应用前景。
