Grupo de Investigación en Sustancias Bioactivas, Sede de Investigación Universitaria, Universidad de Antioquia, AA 1226 Medellín, Colombia.
Rapid Commun Mass Spectrom. 2009 Nov;23(21):3361-71. doi: 10.1002/rcm.4253.
Through the action of glycosyltransferases, a plant can biosynthetically assemble small different aglycons or 'templates' to various polysaccharides to produce numerous glycoconjugates differing in the type of the attached aglycon, the anomeric configuration of C-1 of the glycosylating sugar, the type of sugar and the different position of attachments of the sugar unit present in the polysaccharide chain. The position of attachments and the anomeric configuration of the different sugar present in the polysaccharide create the opportunity to generate molecules with either the same or very close molecular weights, which have relative structural similarity--forming isobaric and positional isomers. Although isomeric differentiation was once considered outside of the domain of mass spectrometry, this task can now be resolved using tandem mass spectrometry. In a standardized purified glycoconjugate fraction (SPT01) from Phytolacca bogotensis, we report conventional electrospray ionization mass spectrometry and collision-induced dissociation (CID) MS/MS parameters which favored the formation of characteristic product ions. This allowed us to suggest the type of sugar linkages present in a specific glycoconjugate. Ten new glycoconjugate are described from this plant and another twelve known saponins were structurally characterized using the automatic MSn acquisition mode. The differentiation of two pairs of positional isomers and four isobaric glycosides and the production of a library of 30 glycosides present in P. bogotensis were accomplished.
通过糖基转移酶的作用，植物可以生物合成地将不同的小非糖部分或“模板”组装到各种多糖上，从而产生在连接的非糖部分、糖基化糖的 C-1 的端基构型、糖的类型以及多糖链上存在的糖单元的不同连接位置方面存在差异的众多糖缀合物。多糖中存在的不同糖的连接位置和端基构型为生成分子量相同或非常接近、相对结构相似的分子提供了机会——形成等质量和位置异构体。尽管异构体的区分曾经被认为超出了质谱的范围，但现在可以使用串联质谱来解决这个问题。在 Phytolacca bogotensis 的标准化纯化糖缀合物级分 (SPT01) 中，我们报告了有利于形成特征性产物离子的常规电喷雾电离质谱和碰撞诱导解离 (CID) MS/MS 参数。这使我们能够确定特定糖缀合物中存在的糖键类型。从这种植物中描述了十个新的糖缀合物，并用自动 MSn 采集模式对另外十二个已知皂苷进行了结构表征。实现了对两对位置异构体和四个等质量糖苷的区分，以及构建了存在于 P. bogotensis 中的 30 个糖苷的文库。
