电喷雾离子源正离子模式下环烯醚萜苷的质谱裂解行为

利用高分辨率四极杆-飞行时间串联质谱(Q-TOF MS/MS)对环烯醚萜苷同系组分7,8-环戊烯型和环戊烷型环烯醚萜苷在电喷雾正离子(ESI⁺)模式下的质谱裂解行为进行了研究. 在ESI⁺模式下, 环烯醚萜苷主要的质谱裂解途径是脱去母环上的功能基团, 如丢失H₂O, CO₂, CH₃OH, CH₃COOH和糖单元部分等, 由于它们均为葡萄糖苷, 所以共有碎片离子Glc+Na]⁺(m/z 185.0). 环烯醚萜苷母核环上半缩醛结构的异构化造成二氢吡喃环的断裂, 但未发现与苷元部分在负离子(ESI^-)模式下相同的其它断裂. 环烯醚萜苷在ESI⁺模式下的断裂途径特征性不如其在ESI^-模式下的明显, 且灵敏度比后者低.

Electrospray Ionization Quadrupole Time-of-flight Tandem Mass Spectrometry of Iridoid Glucosides in Positive Ion Mode

The mass spectral fragmentation behaviors of iridoid glucosides(IGs) was studied via electrospray ionization(ESI) quadrupole time-of-flight tandem mass spectrometry(Q-TOF MS/MS) in the positive ion mode. The homogeneous IGs, such as 7,8-cyclopentene-type and cyclopentane-type IGs, the main and typical losses of these classes of compounds are the H2O, CO2, CH3OH, CH3COOH and a glucosidic unit, which indicate the presence of OH, COOH, COOCH3, CH3COO and glucosidic groups on the aglycone moiety. The common fragment ion Glc+Na]+(m/z 185.0) was detected, due to the existence of glucosidic unit. In addition, the cleavages of the dihydro-pyranoid ring were observed in the different sub-classes, but no cleavages were observed in other parts of the aglycone moieties and glucosidic units. The mass spectral fragmentation patterns of IGs in positive ion mode were less characteristic than those in negative ion mode, and the ion intensities were also weaker than those in negative ion mode.