Hu Dan, Cai Tian, Wang Wei-Ying, Ye Li-Ming, Wu Zhi-Jun
1 West China School of Pharmacy, Sichuan University, Chengdu, China.
2 Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, China.
Eur J Mass Spectrom (Chichester). 2017 Jun;23(3):122-126. doi: 10.1177/1469066717699217. Epub 2017 Mar 27.
A series of coumarins were analyzed using electrospray ionization quadrupole time-of-flight tandem mass spectrometry in the positive-ion mode. Unexpected hydrated ions ([M + HO + Na]) was observed upon collision-induced dissociation of the sodiated ions ([M + Na]) of eight coumarins. Several factors which affected relative abundance of [M + HO + Na] ions such as collision energy, concentration and solvent were investigated. None of them have effect on the relative abundance of [M + HO + Na]. However, the peak of hydrated ions was not detected in the further collision-induced dissociation of protonated ions of coumarins. Apigenin and Quercetin sharing similar benzopyrone structural unit with coumarins are selected for tandem mass spectrometry analysis. There were no hydrated ions in their tandem mass spectrometry spectra of the precursor [M + Na] ions. Thus, both coumarins and sodium were necessary for the formation of [M + HO + Na]. Together with the result that hydrated ions are not formed by hydrolysis reactions, a six-membered ring structure which involves with the formation of [M + HO + Na] was presented. And D-labeling experiment indicates that the HO molecule did not come from solvent.
采用电喷雾电离四极杆飞行时间串联质谱在正离子模式下对一系列香豆素进行了分析。在对8种香豆素的钠化离子（[M + Na]）进行碰撞诱导解离时，观察到了意外的水合离子（[M + HO + Na]）。研究了碰撞能量、浓度和溶剂等影响[M + HO + Na]离子相对丰度的几个因素。它们均对[M + HO + Na]的相对丰度没有影响。然而，在香豆素质子化离子的进一步碰撞诱导解离中未检测到水合离子峰。选择与香豆素具有相似苯并吡喃结构单元的芹菜素和槲皮素进行串联质谱分析。在它们前体[M + Na]离子的串联质谱图中没有水合离子。因此，香豆素和钠对于[M + HO + Na]的形成都是必需的。结合水合离子不是由水解反应形成的结果，提出了一种涉及[M + HO + Na]形成的六元环结构。氘标记实验表明HO分子并非来自溶剂。
