积雪草苷和羟基积雪草苷的电喷雾质谱裂解机制研究

以积雪草苷和羟基积雪草苷为研究对象,在正负离子模式下,获得其电喷雾离子阱三级质谱图,结合分子模拟方法,解析了其正负离子模式下二级质谱中基峰子离子的三级质谱裂解途径,并寻找其裂解规律。结果表明,以上两种皂苷化合物在正负离子模式下,分子离子均发生苷键的断裂,主要生成苷糖基的碎片离子;苷糖基在三级质谱裂解中主要发生脱水和交叉环切除的裂解反应,其质谱裂解途径应遵循苷糖基的脱水和缩环时不破坏分子内氢键的裂解规律。应用密度泛函(DFT)方法优化得到苷糖基能量最低的稳定构型,利用氢键识别模块对苷糖基可能形成的分子内氢键及其位置进行了预测。实验结果表明,推测的正负碎片离子与质谱裂解结果相符,从而验证了以上苷糖基的脱水和缩环规律的合理性。本实验结果丰富了乌苏烷型皂苷的电喷雾质谱裂解规律,可为乌苏烷型皂苷的结构鉴定提供更多支持。

Fragmentation Pathways and Patterns of Asiaticoside and Madecassoside in ESI-MSn

To study the fragmentation pathways and patterns of asiaticoside and madecassoside by electrospray ionization mass spectrometry (ESI-MSⁿ), the two compounds were analyzed by HPLC-ESI-MSⁿ in positive ion mode and negative ion mode respectively, and multi-stage mass spectrum diagrams of the above two compounds were obtained. Mass spectrometry fragments of asiaticoside and madecassoside were analyzed under positive ion mode and negative ion mode, the stable configuration of sugar ions having the lowest energy was determined by calculation with density functional theory (DFT), and the fragments from the above two compounds mainly were the fragments of the anthocyanin glycosylation after the Glycoside bond of the molecular breaked, and dehydration and cracking rings occured in the fragments of the anthocyanin glycosylation in which the intramolecular hydrogen bonds were not destroyed. The intramolecular hydrogen bonding and dehydrogenation position in the anthocyanin glycosylation were predicted by calculating the molecular space bond length by Monitor Hbonds in the soft Discovery Studio 4.0, from which the positive and negative ions inferred are accord with the anthocyanin glycosylation fragments in the experiment, which confirms the rationality of the law of dehydration and cracking rings in the anthocyanin glycosylation fragments were guided by the law of dehydration and cracking rings of the anthocyanin glycosylation. The fragmentation pathways of the anthocyanin glycosylation fragments are explained by the calculation of the quantum chemistry at a molecular level, and can provide the basis for the chemical structure identification of ursane saponins.