女贞子中裂环环烯醚萜苷在UPLC-Q TOF MS/MS负离子模式下的结构表征

Identification of secoiridoid glycosides in Ligustri Lucidi Fructus extract by UPLC-Q TOF MS/MS in negtive ion mode

目的:探究裂环环烯醚萜苷(secoiridiod glycosides,SIGs)同系组分的质谱裂解规律,并将其应用于中药材复杂体系该类化合物的结构表征。方法:利用超高效液相色谱-四极杆飞行时间串联质谱(UPLC-Q TOF MS/MS)在大气压化学电离源负离子模式下(APCI^(-))对4个SIGs同系组分(龙胆苦苷、獐芽菜苦苷、女贞苷、特女贞苷)的质谱裂解行为进行探究。色谱柱为InfinityLab Poroshall120 EC-C_(18)(150 mm×2.1 mm,2.7μm),流动相为乙腈-0.1%(v/v)甲酸水溶液,梯度洗脱;质谱雾化气和辅助气压力均为345 kPa,气帘气压力为241 kPa,离子源温度为550.0℃,喷雾电压为5.5 kV,碰撞诱导电压为30 V,离子质量扫描范围为m/z 50~1000。在此条件下,归纳总结该同系组分的质谱裂解规律,并应用于女贞子中SIGs的结构表征。结果:在APCI^(-)模式下,依据碎片离子的精确质量数和元素组成,SIGs同系组分除了常见的中性丢失,如丢失一分子葡萄糖基(-162)及一分子H_(2)O外,SIGs特征的断裂途径是苷元部分发生的retro-Diels-Alder(RDA)断裂。另外,在APCI^(-)下,SIGs葡萄糖基的断裂,不仅生成^(0,4)A_(1)^(-)(m/z 119.0)、^(1,4)A_(1)^(-)(m/z 89.0)及^(2,4)A_(1)(m/z 59.0)碎片离子,还生成[glucose-H_(2)O]^(-)(m/z 161.0),[glucose-CH_(2)O]^(-)(m/z 149.1)以及[glucose-CH_(2)O-H_(2)O]^(-)(m/z 131.1)碎片离子。对上述SIGs同系组分的质谱裂解行为进行归纳总结,依据其裂解规律利用UPLC-Q TOF MS/MS对女贞子提取物中的SIGs进行了表征,共初步鉴定出16个SIGs,其中包括5组13个同分异构体。结论:依据SIGs同系组分的质谱裂解规律,更有利于复杂体系中该类化合物的物质基础研究。

Objective:To explore the mass spectral fragmentation patterns of the homologous secoiridiod glycosides(SIGs),and apply it to the chemical identification of the complex system.Methods:The mass spectral fragmentation behaviors of 4 standard SIGs,including gentiopicroside,swertiamarin,nuezhenoside and specnuezhenide,werestudied in negative atmospheric pressure chemical ionization(APCI^(-))by UPLC-Q TOF MS/MS.An infinitylab poroshall 120 EC-C_(18) column(150 mm×2.1 mm,2.7μm)was used for separation of SIGs.The elution system consisted of acetonitrile and 0.1%(v/v)formic acid aqueous solution with gradient elution.The nebulizer and auxiliary gas pressure were both set at 345 kPa,and the curtain gas pressure was set at 241 kPa.The desolvation temperature was set at 550.0℃.The spray voltage was set at 5.5 kV,and the collision energy was set at 30 V.The spectra scan range was from m/z 50 to 1000.Under those conditions,the fragmentation patterns of SIGs were summarized and applied to the structural characterization of the SIGs from Ligustri Lucidi Fructus.Results:In APCI-mass spectra,not only the frequently occurring neutral losses,such as glucosidic unit and H_(2)O were detected,but also the characteristic retro Diels Alder(RDA)cleavage of the aglycon moiety were observed,based on accurate mass measurements and the elemental compositions of the product ions.Besides,^(0,4)A_(1)^(-)(m/z 119.0)、^(1,4)A_(1)^(-)(m/z 89.0)and^(2,4)A_(1)^(-)(m/z 59.0)ions,and fragment ion of[glucose-H_(2)O]^(-)(m/z 161.0),[glucose-CH_(2)O]-(m/z 149.1),[glucose-CH_(2)O-H_(2)O]^(-)(m/z 131.1)were observed due to the ring cleavages of the sugar moieties.Based on the fragmentation patterns of these 4 reference substance SIGs,16 SIGs,which contains 13 isomers in 5 groups,have been characterized in the extract of Ligustri Lucidi Fructus by UPLC-Q TOF MS/MS in negative ion mode.Conclusion:According to the mass spectral fragmentation patterns of the SIGs,it is more conducive to the material component study of such compounds in complex system.