摘要
同分异构体在中药中广泛存在,而能量分辨质谱技术已被用于同分异构体的区分。然而,传统的能量分辨质谱主要通过针泵注射对照品来进行,难以实现高通量、自动化分析。该文利用LC-MS实现能量分辨质谱的在线化,并以中药中广泛分布的山柰酚和木犀草素这一对同分异构体为例,阐述在线能量分辨质谱在同分异构体区分中的应用。通过LC-QE-OrbitrapMS获得山柰酚和木犀草素的高分辨质谱数据,并对裂解途径进行了推导,发现两者的准分子离子峰均为m/z 285[M-H]-,通过RDA裂解产生相同的碎片离子m/z 151和133。进一步利用LC-Qtrap-MS平台,构建特征离子对m/z 285>151和285>133,两者均衍生出1组拟离子对(PITs),赋予每1组拟离子对系列递进式的碰撞能(如-5、-8、-11 eV等),利用多反应监测模式采集各拟离子对的峰面积。每组拟离子对的响应值均采用高斯曲线拟合得到裂解曲线,定义裂解曲线顶点为最佳碰撞能(OCE),分别计算山柰酚和木犀草素不同离子对的OCE。对于离子对m/z 285>151,山柰酚和木犀草素的OCE分别为-29.06 eV和-35.71 eV,山柰酚和木犀草素m/z 285>133的OCE分别为-44.15 eV和-49.01 eV。由于羟基取代位置的不同,化学键断裂所需的能量也不尽相同,使得山柰酚和木犀草素不同离子对的OCE均存在显著差异。因此,在线能量分辨质谱能够实现同分异构体的高效区分,为基于LC-MS的复杂体系中化学成分的准确鉴定提供了参考。
Isomers are widely distributed in Chinese herbal medicines,and can be discriminated by energy-resolved mass spectrometry(ER-MS).However,ER-MS was performed through direct injection of reference compounds with syringe pump,which encountered a significant technical barrier for high-throughput and automated measurements.Herein,online ER-MS was conducted using LC-MS platform,and a pair of isomers,kaempferol vs luteolin,were employed as a case study to illustrate and assess the utility of online ER-MS for isomeric discrimination.High-resolution tandem mass spectrometry data of both flavonoids were acquired on LC-QE-Orbitrap-MS,and the fragmentation pathways responsible for the primary fragment ions were proposed.The primary signal in MS1 occurred at m/z 285([M-H]-),and the primary signals of either compound generated by retro-Diels-Alder fragmentation were observed at m/z 151 and 133.The spectral information was subsequently transferred onto LC-Qtrap-MS platform to carry out online ER-MS.Two precursor-to-product ion transition candidates were constructed as m/z 285>151 and 285>133,and either afterward derived a set of pseudo-ion transitions(PITs)and so forth,exactly corresponding to a series of progressive collision energies(eg-5,-8,-11 eV,and so on).All PITs were typed into the monitoring list of multiple reaction monitoring program to generate the peak area datasets.Either dataset was normalized using the highest values in the set and imported into GraphPad Prism software to plot the Gaus-sian-shaped curve that was termed as the break-down graph.The apex of the regressive curve was termed as optimal collision energy(OCE).The OCE values corresponding to m/z 285>151 were calculated as-29.06 eV and-35.71 eV for kaempferol and luteolin,respectively.In the case of m/z 285>133,the OCEs were yielded as-44.15 eV for kaempferol and-49.01 eV for luteolin.With re-ference to their chemical structures,the location of hydroxyl group was regarded to be responsible for the differences of either m/z 285>151 or 285>133 between the isomers,attributing to their different bond properties.Above all,online ER-MS offers an eligible tool for isomeric discrimination,and provides meaningful information for the accurate chemical composition characterization based on LC-MS,which is not limited to Chinese herbal medicines.
作者
汤慧婷
姜俊
曹妍
管朋维
李菡
赵依佳
于娟
屠鹏飞
李军
宋月林
TANG Hui-ting;JIANG Jun;CAO Yan;GUAN Peng-wei;LI Han;ZHAO Yi-jia;YU Juan;TU Peng-fei;LI Jun;SONG Yue-lin(Modern Research Center for Traditional Chinese Medicine,School of Chinese Materia Medica,Beijing University of Chinese Medicine,Beijing 100029,China;Shandong Institute for Food and Drug Control,Ji'nan 250100,China;Zhangzhou Pien Tze Huang Pharmaceutical Co.,Ltd.,Zhangzhou 363000,China)
出处
《中国中药杂志》
CAS
CSCD
北大核心
2021年第14期3599-3604,共6页
China Journal of Chinese Materia Medica
基金
国家重点研发计划项目(2018YFC1707300)
国家自然科学基金项目(81773875,81530097)
中国科协青年人才托举工程项目(2017QNRC001)
北京中医药大学青年科学家培育计划项目(BUCM-2019-QNKXJB006)。
关键词
在线能量分辨质谱
山柰酚
木犀草素
裂解曲线
online energy-resolved mass spectrometry
kaempferol
luteolin
breakdown graph
作者简介
汤慧婷,硕士研究生,E-mail:A20160222015@163.com;通信作者:宋月林,研究员,博士生导师,研究方向为中药质量评价和药效物质基础,E-mail:syltwc2005@163.com;通信作者:李军,研究员,博士生导师,研究方向为中药及其复方化学和生物活性,E-mail:drlj666@163.com。
