Structural characterization of iridoid glucosides by ultra‐performance liquid chromatography/electrospray ionization quadrupole time‐of‐flight tandem mass spectrometry

Abstract

The mass spectral fragmentation behavior of ten iridoid glucosides (IGs) has been studied using electrospray ionization (ESI), collision-induced dissociation (CID), and quadrupole time-of-flight tandem mass spectrometry (Q-TOF MS/MS). In the negative ESI mass spectra, the deprotonated [M-H](-) ion was observed for all of the ten IGs except gardoside methyl ester, while the formate adduct [M+HCOO](-) ion appeared to be favored by the presence of a methyl ester or a lactone group in the C-4 position when formic acid was added to the mobile phase. The CID MS/MS spectra of the [M-H](-) ions have been used for structural elucidation. Ring cleavages of the aglycone moiety have been observed in the MS/MS spectra, corresponding to (1,4)F(-), (2,6)F(-), (2,7)F(-), and (2,7)F(0) (-) ions, based on accurate mass measurements and the elemental compositions of the product ions. These characteristic ions gave valuable information on the basic structural skeletons. Furthermore, on the basis of the relative abundances of the fragment ions (1,4)F(-) and (2,7)F(-), different sub-classes, such as cyclopentane-type and 7,8-cyclopentene-type IGs, can be differentiated. Ring cleavage of the sugar moieties was also observed, yielding useful information for their characterization. In addition, the neutral losses, such as H(2)O, CO(2), CH(3)OH, CH(3)COOH, and glucosidic units, have proved useful for confirming the presence of functional substituents in the structures of the IGs. Based on the fragmentation patterns of these standard IGs, twelve IGs have been characterized in an extract of Hedyotis diffusa Willd. by means of ultra-performance liquid chromatography/Q-TOF MS/MS, of which six have been unambiguously identified and the other six have been tentatively identified.

Analysis of iridoid glucosides from Paederia scandens using HPLC–ESI-MS/MS

“…The product ion at m/z 121 was produced by the retro Diels-Alder (RDA) reaction from m/z 191. For 2, a high abundance [M+CH 3 COO]− ion was detected in negative ion mode, as reported previously [18]. It seemed that the [M+CH 3 COO]− ion was negligible when carboxyl was present.…”

“…1), and was the main compound in the extract of P. scandens. Compound 2 may The molecular formula of compounds 3 was confirmed as C 18 H 24 O 12 , and the MS/MS spectrum of this compound was very similar to that of 1. This indicates that the skeleton structure of 3 is the same as that of 1, and the data suggested that the former may be asperulosidic acid (3) ( Fig.…”

Fragmentation study of iridoid glycosides and phenylpropanoid glycosides in Radix Scrophulariae by rapid resolution liquid chromatography with diode‐array detection and electrospray ionization time‐of‐flight mass spectrometry

“…Therefore, the development of simple and rapid methods for the analysis of complex compositions is of great signifi cance in the quality control of herbal medicine. Nowadays, high-performance liquid chromatography (HPLC) coupled with mass spectrometry (MS) has been proved to be a very useful tool applied to the characterization of constituents in medicinal herbs (Qi et al, 2008;Li et al, 2008;Es-Safi et al, 2007). The systematic structural characterization of the compounds in Radix Scrophulariae with mass spectrometric method has, to our knowledge, not been examined, and is thus interesting from a phytochemical and analytical point of view.…”

Genome sequence and genetic diversity of European ash trees

“…7). The MS/MS fragmentation network was generated after extracting the m/z values of the MS/MS product ions from the discriminatory features using MassHunter Qualitative Analysis Version 4 and visualized using Cytoscape, indicating product ion masses that had been previously reported from fragmentation of iridoid glycosides 110 .…”