Studies of iridoid glycosides using liquid chromatography/electrospray ionization tandem mass spectrometry

Abstract

Fragmentation pathways of five iridoid glycosides have been studied by using electrospray ionization multi-stage tandem mass spectrometry (ESI-MS(n)). The first-stage MS data of the five iridoid glycosides were compared. The MS spectra showed that the adduct ions of iridoid glycosides and the formate anion were diagnostic ions to distinguish iridoid glycosides with a carboxyl group at the C-4 position or an ester group at the C-4 position. The MS fragmentation pathways of the five iridoid glycosides were also studied. Analyzing the product ion spectra of iridoid glycosides, some neutral losses were observed, such as H(2)O, CO(2) and glucose residues, which were very useful for the identification of the functional groups in the structures of iridoid glycosides. Furthermore, specific loss of one molecule of methyl 3-oxopropanoate or 3-oxopropanic acid was firstly discussed, which corresponded to the isomerization of the hemiacetal group in the structure of iridoid aglycone. According to the fragmentation mechanisms and HPLC/MS(n) data, the structures of five iridoid glycosides in a crude extract of Gardenia jasminoisdes fruit have been identified. Three compounds were compared with standards and the other two were identified as shanzhiside and genipin gentibioside by their MS(n) data without standard compounds. In order to further validate the veracity of the deduction, genipin gentiobioside was isolated from the extract of Gardenia jasminoisdes fruit using Purification Factory and was further identified by C- and H-NMR.

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

“…The fragmentation was followed by successive losses of H 2 O, which produced another two major peaks with m/z at 183.0664 and 165.0555. On the other hand, ring cleavages of the aglycone moieties (Ren et al, 2007) were also observed in the spectra. The product ions, such as those at m/z 157.0506 and 139.0399, were characteristic fragments produced by ring cleavage of the basic skeletons, which provided valuable information characterizing the basic structural skeleton.…”

Gas‐phase dissociation of 1,4‐naphthoquinone derivative anions by electrospray ionization tandem mass spectrometry

“…The fragmentation pathways of [M − H] − are usually applied to molecules with acid groups, such as carboxylic acids and phenols. [16,17] Recently, Levsen and coworkers [18] have applied CID to protonated and deprotonated molecules generated by ESI or atmospheric pressure chemical ionization (APCI [18] which has furnished important data for MS/MS users.…”

Identification and Structure Elucidation of Compounds from Herbal Medicines

“…More detailed elucidation for fragmentation of iridoids in negative ion mode can be found in reference literature. 26,65 …”