Figure 2.

Negative-ion ESI-mass and tandem mass spectra of 3-O-[β-D-glucuronopyranosyl]-28-O-[β-xylopyranosyl(1 → 4)-α-L-rhamnopyranosyl (1 → 2) - α-L-arabinopyranoside medicagenate (3-GlcA-28-AraRhaxyl-medicagenate).(A) the ESI-mass spectrum of the isotope distribution of the (M-H)- ion at m/z 1087.33, of 3-GlcA-28-AraRhaxyl-medicagenate, (B) MS/MS of 3-GlcA-28-AraRhaxyl-medicagenate, precursor ion is m/z 1087.3, fragment ion at m/z 911.3 correlates to the loss of glucuronic acid (GlcA), (C) MS3 of 3-GlcA-28-AraRhaxyl-medicagenate, precursor ion is m/z 911.3, fragment ion at m/z 501.4 correlates to the sequential loss of sugar substituents arabinose, rhamnose and xylose (Ara-Rha-xyl) and thus the fragment ion at m/z 501.4 corresponds to M-H mass of medicagenic acid.

Da Silva et al. BMC Chemical Biology 2012 12:3   doi:10.1186/1472-6769-12-3
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