Núcleo de Pesquisas em Ciências Exatas e Tecnológicas, Universidade de Franca, 14404-600 Franca-SP, Brazil.
Rapid Commun Mass Spectrom. 2010 Feb;24(3):295-308. doi: 10.1002/rcm.4389.
The fragmentation of six plumeran indole alkaloids (PIAs) previously isolated from Aspidosperma spruceanum has been investigated by electrospray ionization tandem mass spectrometry (ESI-MS/MS) in the positive ion mode. The fragmentation pathways have been established on the basis of MS/MS experiments using fragment ions generated in-source and deuterium-labeled alkaloids as precursor ions and on the basis of accurate mass measurements. Our results demonstrated that the fragmentation routes observed for the protonated PIAs are essentially derived from a pericyclic reaction and from the opening of rings D and E, followed by 1,4-hydrogen rearrangements. Product ions resulting from radical eliminations were also observed, contrary to the 'even-electron rule'. Our data reveals that some product ions from protonated PIAs provide crucial information for the characterization of the acyl substituent at N-1, the methoxyl and hydroxyl groups at the aromatic moiety, and give evidence of an ether bridge between C-18 and C-21. The data reported here were used for the dereplication of these compounds in a stem bark methanolic extract of Aspidosperma spruceanum.
已通过电喷雾串联质谱（ESI-MS/MS）在正离子模式下对先前从 Spruceanum 中分离出的六种 Plumeran 吲哚生物碱（PIA）进行了片段化研究。基于源内产生的碎片离子和氘标记生物碱作为前体离子进行的 MS/MS 实验以及精确质量测量，建立了碎裂途径。我们的结果表明，观察到的质子化 PIA 的碎裂途径主要源自周环反应和环 D 和 E 的打开，随后发生 1,4-氢重排。还观察到自由基消除产生的产物离子，这与“偶数电子规则”相反。我们的数据表明，一些质子化 PIA 的产物离子为 N-1 上的酰基取代基、芳基部分的甲氧基和羟基以及 C-18 和 C-21 之间的醚桥的表征提供了关键信息。这里报道的数据用于对 Spruceanum 的茎皮甲醇提取物中这些化合物的去重复鉴定。
