儿茶素与咖啡碱络合物的晶体学研究  

Crystallographic Study on the Complex of Catechins and Caffeine

作　　者：董燕茹 曹妍彦 卢佳纯 梅思凡 河润 陈萍[1] DONG Yanru;CAO Yanyan;LU Jiachun;MEI Sifan;HE Run;CHEN Ping(Tea Research Institute,Zhejiang University,Hangzhou 310058,China)

机构地区：[1]浙江大学茶叶研究所,浙江杭州310058

出　　处：《茶叶科学》2021年第1期80-89,共10页Journal of Tea Science

摘　　要：通过高效液相色谱分析发现儿茶素和咖啡碱占绿茶乳酪总质量的88%以上。以乳酪中含量最高的两种酯型儿茶素和对应的非酯型儿茶素与咖啡碱络合建立绿茶乳酪简化体系CATs-CAF,发现4种儿茶素在沉淀中的分布比例为EC∶ECG∶EGC∶EGCG≈1∶2∶1∶2。选用ECG和EC分别与咖啡碱络合制备单晶,扫描电镜观察络合前后晶体的显微形貌,X-射线单晶衍射分析立体化学结构。结果表明,两种络合物晶体均为针状,通过分子间氢键和面对面π-π堆积作用形成。其中,EC可与相邻EC、CAF分子形成O-H...O型氢键,通过A环和CAF的六元环发生π-π堆积,形成1∶1络合物;而ECG可与相邻ECG、CAF分子形成O-H...O型氢键以及O-H...N型氢键,并且所有芳香环均能与CAF发生π-π堆积,形成2∶4络合物,每个ECG的A环、B环可分别与相邻两个ECG的B环、A环共用CAF的六元环,而ECG的D环和CAF的六元环则通过两种排列方式在a轴上延伸。Through HPLC analysis,it was found that catechins and caffeine accounted for more than 88%of the total mass of green tea cream.The CATs-CAF,a simplified green tea cream system,was established by two ester catechins that with the highest content in green tea cream,and their corresponding non-ester catechins complexed with caffeine.The distribution ratio of 4 catechins in precipitate was that EC∶ECG∶EGC∶EGCG≈1∶2∶1∶2.Single crystals were prepared by complexing ECG and EC respectively with caffeine and observed under scanning electron microscopy to record their micro-morphology before and after complexation.Using X-ray single-crystal diffraction to analyze the stereochemical structure,the results show that two needle crystals were formed by intermolecular hydrogen bonding and face-to-faceπ-πstacking.EC formed O-H...O type hydrogen bonds with adjacent EC and CAF molecules,andπ-πstacking occurred between the A ring of EC and the six-membered ring of CAF to form a 1∶1 complex of EC-CAF.While the ECG could form O-H...O and O-H...N type hydrogen bonds with adjacent ECG and CAF molecules,and theπ-πstacking of ECG-CAF occurred among all aromatic rings to form a 2∶4 complex,in which the ring A and B of each ECG shared the six-membered ring of CAF separately with the ring B and A of the adjacent ECGs,while the D ring of ECG and the six-membered ring of CAF extended on the a axis in two arrangements.

关 键 词：茶乳酪 络合机理 扫描电镜 X-射线单晶衍射 

分 类 号：S571.1[农业科学—茶叶生产加工] O723.6[农业科学—作物学]