4种儿茶素类化合物电喷雾质谱裂解规律的研究

利用离子阱飞行时间质谱仪的高质量精度、高分辨率及多级测定性能, 对儿茶素类化合物(二组对映异构体)质谱裂解进行研究, 并利用氢/氘交换法对裂解方式进行确证. 发现儿茶素对映异构体间具有相同的质谱裂解途径, 多级质谱无明显区别. 在二级质谱中, 表儿茶素/儿茶素(EC/C)丢失的CO₂发生在A环, 丢失的C₂H₂O发生在B环. ^1,4A^-, ^1,3A^-, ^1,2A^-和M-H-B环]^-4个碎片离子为EC/C特征离子, 通过这4个离子质量数变化, 推测A环上的取代情况. 因表儿茶素没食子酸酯/儿茶素没食子酸酯(ECG/CG)结构上都含有没食子酸取代基, 在二级质谱中均可见m/z169特征峰, 此离子可用于ECG/CG和EC/C区分.

ESI Fragmentation Studies of Four Tea Catechins

The fragmentation pathways of tea catechins(two group stereoisomers ) were studied via the ion-trap time-of-flight(IT-TOF) mass spectrometer with the advantages of high mass accuracy, high resolution, multistage analysis. Hydrogen/deuterium exchange method was used to elucidate the fragmentation processes. The results show that catechin stereoisomers possess the same fragmentation pathways and cannot be differen-tiated even in MSn spectra. We can locate the loss of CO2 and C2H2O in MS2 spectra from EC/C to A ring and B ring, respectively. The ions of 1,4A-, 1,3A-, 1,2A- and M-H-B ring]- were characteristic product ions for EC/C, and it could be used to propose the substituent group of A ring through the m/z shift of these ions. The ion at m/z 169 corresponding to the gallic acid anion was characteristic fragmentation of ECG/CG, which was great helpful for differentiating ECG/CG and EC/C.