Enhanced metabolite identification with MS^E and a semi-automated software for structural elucidation

Abstract

The identification of metabolites is almost exclusively done with liquid chromatography/tandem mass spectrometry (LC/MSMS) and despite the enormous progress in the development of these techniques and software for handling of data this is a time-consuming task. In this study the use of quadrupole time-of-flight (QTOF)-generated MS(E) and MS/MS data were compared with respect to rationalization of metabolites. In addition Mass-MetaSite, a semi-automated software for metabolite identification, was evaluated. The program combines the information from MS raw data, in the form of collision-induced dissociation spectra, with a prediction of the site of metabolism in order to assign the structure of a metabolite. The aim of the software is to mimic the rationalization of fragment ions performed by a biotransformation scientist in the process of structural elucidation. For this evaluation, metabolite identification in human liver microsomes was accomplished for 19 commercially available compounds and 15 in-house compounds. The results were very encouraging and for 96% of the metabolites the same structures were assigned using MS(E) compared with MSMS acquired data. The possibility of using MS(E) could considerably reduce the analysis time. Moreover, Mass-MetaSite performed well and the correct assigned structure, compared to manual inspection of the data, was picked in the first rank in ∼80% of the cases. In conclusion MS(E) could be successfully used for metabolite identification in order to reduce time of analysis and Mass-MetaSite could alleviate the work of a biotransformation scientist and decrease the workload by assigning the structure for a majority of the metabolites.

Utilizing Microchip Capillary Electrophoresis Electrospray Ionization for Hydrogen Exchange Mass Spectrometry

“…To the best of our knowledge, this work represents the fastest ever utilization of MS E . In 2010, Bonn et al reported LC-MS E of metabolites with a summed scan time of 100 ms. 29 In this manuscript, the summed scan speed was 50 ms, sampling twice as fast. Figure S2 in Supporting Information shows representative peaks from both the microchip CE-ESI electropherogram and the LC-MS chromatogram, illustrating the number of MS data points across each peak.…”

Automated Annotation of Microbial and Human Flavonoid-Derived Metabolites

“…A number of methods have been developed that annotate m/z values in a fragmentation spectrum with in silico generated substructures of possible candidate molecules. Methods based on the concept include EPIC [ 22 ] (available as MassFragment software from Waters), Mass-Frontier [ 23 ], FiD [ 24 ], MetFrag [ 25 ] and MassMetaSite [ 26 ]. We recently described an extended algorithm that can handle multistage spectral trees, obtained from LC-MSn experiments, where n > 2 [ 27 ].…”

A critical review on the use of modern sophisticated hyphenated tools in the characterization of impurities and degradation products

“…Subsequently, the energy is increased till reasonable comprehensive fragmentation profile is obtained. A few modern mass spectrometers have the facility of collision energy ramping, along with auto polarity switching, which can be exploited to gain maximum information in a single LC-MS run [143,144]. An important aspect that may need attention at this stage is that during MS runs using atmospheric pressure ionization sources, one usually encounters peaks for adducts of molecular ions with sodium (+22 Da), potassium (+38 Da) and/or ammonium (+17 Da) ions in positive ionization mode, and those due to chloride (+36 Da), acetate (+60 Da) and formate (+46 Da) in the negative mode.…”