实时直接分析质谱法分析中药有效成分的特征气相离子反应机理

Analysis of Characteristic Ion Reactions and Mechanism Exploration of Active Ingredients in Traditional Chinese Medicine by Direct Analysis in Real-Time Mass Spectrometry

本研究采用实时直接分析离子源耦合线性离子阱质谱(DART-LTQ MS)法分析中药有效成分,并优化DART-LTQ MS的质谱参数、离子化温度和工作气体种类等条件。在最优条件下,以N_(2)和He作为DART离子源工作气体,发现不同结构的中药有效成分在N_(2)/He-DART MS中产生了一系列有规律的特征离子,并总结其气相离子特征反应规律。如,采用N_(2)-DART MS分析中等极性的低沸点化合物时,原位发生了有规律的特征离子反应,主要包括氧化反应([M+nO+H]^(+)或[M+nO-H]^(-)(n=1,2,3,4,5))和脱氢反应(损失了2个H,[M-2H±H]^(±));采用He-DART MS分析具有强极性、高沸点的苷类化合物时,在四甲基氢氧化铵(TMAH)辅助下,迅速发生了甲基化反应([M+nCH_(2)+H]^(+)、[M+nCH_(2)+(CH_(3))_(3)NH]^(+)或[M+nCH_(2)-H]^(-)(n=1,2,3,4,5))。另外,根据特征离子推断可能的反应机理,并对相关反应产生的特征母离子进行串联质谱实验,验证所推测机理的准确性。该方法可为中药有效成分的快速分析提供技术支持。

Direct analysis in real-time(DART)ionization source coupled with mass spectrometer can directly and rapidly analyze raw samples in their native environment with high specificity and minimal or no sample preparation.In this study,DART combined with linear ion trap mass spectrometry(DART-LTQ MS)was used to analyze the active components of 33 traditional Chinese medicines and explore the generated gas-phase ion reaction mechanism.The parameters of MS and ion source were optimized,such as ionization gas and temperature.Under the optimized conditions,a series of regular characteristic ions were generated in DART-MS when using N_(2) and He as the ion source working gas.It was found that when N_(2)-DART MS was used to analyze active compounds of low boiling points,regular characteristic ion reactions occurred in situ,mainly including oxidation reaction([M+nO+H]^(+)or[M+n O-H]]^(-)(n=1,2,3,4,5))and dehydrogenation reaction(two hydrogens lost,[M-2H±H]^(±)).The methylation reaction([M+nCH_(2)+H]^(+),[M+nCH_(2)+(CH_(3))_(3)NH]^(+)or[M+nCH_(2)-H]^(-)(n=1,2,3,4,5))occurred when detection of glycosides compound with highly polar and high-boiling by He-DART MS.Furthermore,the characteristic gas ion reaction mechanism of the active components in traditional Chinese medicine was intensively studied,and the exactly related reactions were discussed.The oxidation mechanisms of furanocoumarins and the dehydrogenation mechanisms of dihydroflavonoids were deduced according to the tandem mass spectrometry of the characteristic ion products and the proposed fragmentation pathways.The methylation reaction of glycosides and the action site were verified.And the reaction mechanisms were proposed and further confirmed by tandem mass spectrometry.The rapid analysis of the active ingredients in traditional Chinese medicine by N 2-DART under high temperature and high pressure provides unique and primary characteristics that is difficult to be formed by other methods,which also provides a theoretical reference for future research on the mechanism of DART-MS.This method is rapid,effective,which is suitable for qualitative determination of the active ingredients in traditional Chinese medicine.