A feasible strategy based on isotopic fine structures to enhance the reliability of metabolite identification by Fourier transform ion cyclotron resonance mass spectrometry

Abstract

RationaleIn the process of the identification of unknown metabolites, the most important thing is to determine their real chemical formulae according to the accurate masses which are determined by high‐resolution mass spectrometry. However, high mass accuracy alone is not enough to exclude false candidates. Use of isotopic fine structures (IFSs) derived from Fourier transform ion cyclotron resonance mass spectrometry (FT‐ICR MS) as a single further constraint could decisively determine the molecular formulae for unknown metabolites.MethodsGastrodin, an active constituent from Gastrodia elata Bl., which can penetrate through the blood–brain barrier and rapidly decompose to p‐hydroxybenzyl alcohol in the brain, was selected as a model drug. The accurate masses, possible chemical formulae and IFSs of its metabolites in rat plasma were acquired using FT‐ICR MS.ResultsBesides gastrodin, a total of eight metabolites including two phase I and six phase II metabolites were detected. Their chemical formulae were decisively determined by IFSs. Furthermore, their chemical structures were identified by comparing their fragment ions with those of gastrodin. Results indicated the metabolic pathways of gastrodin in rats including deglycosylation, oxidation, glucuronidation, sulfate conjugation and glycine conjugation.ConclusionsIt is demonstrated that IFSs are effective in unambiguous determination of chemical formulae of metabolites. It could be used as a feasible strategy to enhance the reliability of metabolite identification in drug metabolism studies.

Quality evaluation of natural monomer flavors for Chinese tobacco industry based on dual mode combined Fourier transform ion cyclotron resonance mass spectrometry and isotopic fine structures

“…[15][16][17][18][19] In particular, because of its ultrahigh resolution, the isotopic fine structures (IFSs) of any single molecular ion can be identified and, therefore, its elemental composition can be determined. In other words, FT-ICR-MS can produce unique IFSs of mass peaks to differentiate the tiny mass defects of isotopic contributions such as 2 H, 15 N, 17 O, 18 O, 33 S, and 34 S, as well as 13 C. [18][19][20][21] There is no doubt that, based on this HR-MS technique and the IFSs it provides, FT-ICR-MS has become a powerful tool for identifying the molecular formulas of unknown chemical components in complex systems. 22 Till now, it has been used to identify unknown related substances of cephalosporins, to identify unknown chemical components contained in Chinese herbal medicines, and to identify endogenous unknown metabolites in metabolomics studies.…”

Imaging Matrix-Assisted Laser Desorption/Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry of oxaliplatin derivatives in human tissue sections

“…Thus, the FTICR MSI at high magnetic field provides high mass accuracy (< 1 ppm) and ultra-high resolving power (> 200,000) enabling the separation of most isobaric species. In addition, the resolution obtained during FTICR MS tissue imaging is very suitable for unambiguous molecular formula attribution taking advantage of the Isotopic Fine Structure (IFS) [17][18][19][23][24][25][26]. Therefore, this technique is of great interest for exhaustive analysis, rapid and precise annotation of compounds in biological samples [27] and already have proved its merit for MALDI imaging analysis of biological tissues in terms of resolving power, mass accuracy and dynamic range [27].…”