Mass spectrometric stereoisomeric differentiation between α- and β-ascorbic acid 2-O-glucosides. Experimental and density functional theory study

Authors

  • Basem Kanawati,

    Corresponding author
    1. Institute of Ecological Chemistry, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstr. 1, 85758 Neuherberg, Germany
    • Institute of Ecological Chemistry, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstr. 1, 85758 Neuherberg, Germany.
    Search for more papers by this author
  • Veronica von Saint Paul,

    1. Institute of Biological Plant Pathology, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstr. 1, 85758 Neuherberg, Germany
    Search for more papers by this author
  • Constanze Herrmann,

    1. Institute of Ecological Chemistry, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstr. 1, 85758 Neuherberg, Germany
    Search for more papers by this author
  • Anton R. Schäffner,

    1. Institute of Biological Plant Pathology, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstr. 1, 85758 Neuherberg, Germany
    Search for more papers by this author
  • Philippe Schmitt-Kopplin

    1. Institute of Ecological Chemistry, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstr. 1, 85758 Neuherberg, Germany
    2. Technical University Munich, Department for Chemical-Technical Analysis Research, Center Weihenstephan for Brewing and Food Quality, Weihenstephaner Steig 23, 85354 Freising-Weihenstephan, Germany
    Search for more papers by this author

Abstract

L-Ascorbic acid and two distinct anomers, namely the α-D-glucopyranosyl and β-D-glucopyranosyl-(1→2)-L-ascorbic acid (stereoisomers), were studied within the scope of collision-induced dissociation (CID) experiments, performed by linear ion acceleration and collision with argon atoms inside a hexapole quadrupole hexapole ion beam guide, which is coupled to an ion cyclotron resonance (ICR) cell with a 12 Tesla magnet for high-resolution measurements. Loss of C2H4O2 neutral from the [M–H] anion of L-ascorbic acid was observed. Density functional theory (DFT) calculations on the 6-311+G(2d,p)//6-31+G(d) level of theory reveal a new concerted mechanism for an intramolecular gas-phase rearrangement, through which the observed ejected neutral C2H4O2 can take place. A similar rearrangement also occurs in the case of α- and β-D-glucopyranosyl-(1→2)-L-ascorbic acid. For the α isomer, only homolytic glycoside fragmentation was observed. For the β isomer, both homolytic and heterolytic glycoside cleavages were possible. The mechanisms behind all observed fragmentation pathways were fully understood by the implementation of accurate DFT calculations. Stereoisomeric differentiation between α and β isomers of the L-ascorbic acid-2-O-glucoside could be revealed by tandem mass spectrometry (MS/MS) experiments and were explained theoretically. Copyright © 2011 John Wiley & Sons, Ltd.

Ancillary