Dehydrodimerization of pterostilbene during electrospray ionization mass spectrometry
Type
ArticleKAUST Department
Advanced Nanofabrication, Imaging and Characterization Core LabAnalytical Chemistry Core Lab
Analytical Core Lab
Core Labs
Imaging and Characterization Core Lab
Date
2013-04-30Online Publication Date
2013-04-30Print Publication Date
2013-06-15Permanent link to this record
http://hdl.handle.net/10754/562732
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RATIONALE Pterostilbene is a member of the hydroxystilbene family of compounds commonly found in plants such as blueberry and grapes. During the analysis of this compound by electrospray ionization mass spectrometry (ESI-MS), an ion was observed that corresponds to the dehydrodimer of pterostilbene in mass-to-charge ratio. Since such unexpected dimerization may lead to decreased monomer signal during quantitative analysis, it was of interest to identify the origin and structure of the observed pterostilbene dimer and examine the experimental conditions that influence its formation. METHODS Liquid Chromatography/Mass Spectrometry (LC/MS), Nuclear Magnetic Resonance (NMR), and High-Field Asymmetric Waveform Ion Mobility Spectrometry (FAIMS) were used to examine the origin of the dimerization products. The structure of the formed pterostilbene dimer was examined by performing MSn analysis on the dimer ion. Effects of solvent composition, analyte concentration, radical scavenger, and other experimental conditions on the dimerization were also studied. RESULTS LC/MS and NMR analyses clearly showed that the starting solution did not contain the pterostilbene dimer. Solvent type and radical scavenger concentration were found to have pronounced effects on the dimer formation. Particularly, presence of acetonitrile or ammonium acetate had favorable effects on the extent of dimerization during ESI-MS analysis whereas hydroquinone and butylated hydroquinone had negative effects. Dimer formation decreased at high flow rates and when fused-silica capillary was used as the spray needle. CONCLUSIONS The data indicate that this dimerization occurs as a result of solution-phase electrochemical reactions taking place during the electrospray process. A possible structure for this dimer was proposed based on the MSn analysis and was similar to that of the enzymatically derived pterostilbene dehydrodimer already reported in the literature. Copyright © 2013 John Wiley & Sons, Ltd. Copyright © 2013 John Wiley & Sons, Ltd.Sponsors
The authors gratefully acknowledge research support from the Analytical Core Lab and the NMR Core Lab at the King Abdullah University of Science and Technology, Saudi Arabia. The authors also thank Mr. Salim Sioud, Dr. Zeyad Al-Talla, and Dr. Alain Lesimple for assistance and helpful discussions during the experiments.Publisher
WileyDOI
10.1002/rcm.6571PubMed ID
23650039ae974a485f413a2113503eed53cd6c53
10.1002/rcm.6571