Ren Lingling, Xue Xingya, Zhang Feifang, Wang Yongcan, Liu Yanfang, Li Cunman, Liang Xinmiao
Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China.
Rapid Commun Mass Spectrom. 2007;21(18):3039-50. doi: 10.1002/rcm.3189.
Fragmentation pathways of five iridoid glycosides have been studied by using electrospray ionization multi-stage tandem mass spectrometry (ESI-MS(n)). The first-stage MS data of the five iridoid glycosides were compared. The MS spectra showed that the adduct ions of iridoid glycosides and the formate anion were diagnostic ions to distinguish iridoid glycosides with a carboxyl group at the C-4 position or an ester group at the C-4 position. The MS fragmentation pathways of the five iridoid glycosides were also studied. Analyzing the product ion spectra of iridoid glycosides, some neutral losses were observed, such as H(2)O, CO(2) and glucose residues, which were very useful for the identification of the functional groups in the structures of iridoid glycosides. Furthermore, specific loss of one molecule of methyl 3-oxopropanoate or 3-oxopropanic acid was firstly discussed, which corresponded to the isomerization of the hemiacetal group in the structure of iridoid aglycone. According to the fragmentation mechanisms and HPLC/MS(n) data, the structures of five iridoid glycosides in a crude extract of Gardenia jasminoisdes fruit have been identified. Three compounds were compared with standards and the other two were identified as shanzhiside and genipin gentibioside by their MS(n) data without standard compounds. In order to further validate the veracity of the deduction, genipin gentiobioside was isolated from the extract of Gardenia jasminoisdes fruit using Purification Factory and was further identified by C- and H-NMR.
采用电喷雾电离多级串联质谱（ESI-MS(n)）研究了5种环烯醚萜苷的裂解途径。比较了这5种环烯醚萜苷的一级质谱数据。质谱图显示，环烯醚萜苷与甲酸根阴离子的加合离子是区分在C-4位带有羧基或在C-4位带有酯基的环烯醚萜苷的诊断离子。还研究了这5种环烯醚萜苷的质谱裂解途径。通过分析环烯醚萜苷的产物离子谱，观察到一些中性丢失，如水、二氧化碳和葡萄糖残基，这对鉴定环烯醚萜苷结构中的官能团非常有用。此外，首次讨论了一分子3-氧代丙酸甲酯或3-氧代丙酸的特定丢失，这与环烯醚萜苷元结构中半缩醛基团的异构化相对应。根据裂解机理和HPLC/MS(n)数据，鉴定了栀子果实粗提物中5种环烯醚萜苷的结构。将其中3种化合物与标准品进行了比较，另外2种化合物在没有标准品的情况下通过它们的MS(n)数据鉴定为山栀苷和京尼平龙胆二糖苷。为了进一步验证推导的准确性，使用Purification Factory从栀子果实提取物中分离出京尼平龙胆二糖苷，并通过碳谱和氢谱进一步鉴定。
