Glycoside linkage analyses of medicine and food homologous plant polysaccharides have always been a key point and a difficulty of structural characterization. The gas chromatography–mass spectrometry (GC-MS) method is one of the commonly used traditional techniques to determine glycoside linkages via partially methylated alditol acetates and aldononitrile acetates (PMAAs and PMANs). Due to the simplicity of derivatization and the highly structural asymmetry of PMANs, reverse thinking is proposed using liquid chromatography–electrospray ionization–multiple reaction monitoring mass spectrometry (LC-ESI-MRM-MS) for the first time to directly determine the neutral and acidic glycosyl linkages of polysaccharides. The complete characterization of glycoside linkages deduced from PMANs was achieved using a combination of t_R values, characteristic MRM ion pairs, diagnostic ESI⁺–MS/MS fragmentation ions (DFIs), and optimal collision energy (OCE). The DFI and OCE parameters were confirmed to be effective for the auxiliary discrimination of some isomers of the PMANs. The practicality of LC-ESI⁺-MRM-MS was further verified by analyzing the glycoside linkages of polysaccharides in five medicine and food homologous plants. This method can serve as an alternative to GC-MS for the simultaneous determination of neutral and acidic glycosyl linkages in polysaccharides.

中文翻译：

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基于部分甲基化醛糖腈乙酸酯的逆向思维利用液相色谱-多重反应监测质谱分析多糖的糖苷键


药食同源植物多糖的糖苷键分析一直是结构表征的重点和难点。气相色谱-质谱 (GC-MS) 方法是通过部分甲基化的糖醇乙酸酯和醛糖腈乙酸酯（PMAA 和 PMAN）测定糖苷键的常用传统技术之一。由于衍生化的简单性和PMANs的高度结构不对称性，首次提出利用液相色谱-电喷雾电离-多反应监测质谱（LC-ESI-MRM-MS）直接测定中性和酸性的逆向思路多糖的糖基键。使用 t _R 值、特征 MRM 离子对、诊断 ESI ⁺ –MS/MS 碎片离子 (DFI) 和最佳碰撞能量（OCE）。 DFI和OCE参数被证实对于辅助区分PMAN的某些异构体是有效的。通过对5种药食同源植物多糖苷键的分析，进一步验证了LC-ESI ⁺ -MRM-MS的实用性。该方法可以作为 GC-MS 的替代方法，用于同时测定多糖中的中性和酸性糖基键。