Evidence for linkage position determination in known feruloylated mono- and disaccharides using electrospray ion trap mass spectrometry

Various feruloylated arabinose‐ and galactose‐containing mono‐ and disaccharides with known linkage configurations (2‐O‐(trans‐feruloyl)‐L‐arabinopyranose, 5‐O‐(trans‐feruloyl)‐L‐arabinofuranose, O‐[2‐O‐(trans‐feruloyl)‐α‐L‐arabinofuranosyl]‐(1→5)‐L‐arabinofuranose, and O‐[6‐O‐(trans‐feruloyl)‐β‐D‐galactopyranosyl]‐(1→4)‐D‐galactopyranose) were analyzed by electrospray ionization mass spectrometry using an ion trap or a quadrupole time‐of‐flight (Q‐TOF) mass analyzer. Collision‐induced dissociation (CID) experiments using the two mass analyzers generated similar tandem mass spectrometric (MS/MS) fragmentation patterns. However, the ester‐bond cleavage ions were more abundant using the Q‐TOF mass analyzer. Compared with the positive ion mode, the negative ion mode produces simpler and more useful CID product‐ion patterns. For arabinose‐containing feruloylated compounds, results obtained with both analyzers show that it is possible to assign the location of the feruloyl group to the O‐2 or O‐5 of arabinosyl residues. In the characterization of the 2‐O‐feruloyl and 5‐O‐feruloyl linkages, the relative abundance of the cross‐ring fragment ions at m/z 265 (−60 u or −62 u after 18O‐labelling) and at m/z 217 (−108 u or −110 u after 18O‐labelling) play a relevant role. For galactose‐containing feruloylated compounds, losses of 60, 90 and 120 Da observed in MS3 experiment correspond to the production of 0, 2A1, 0, 3A1 and (0, 2A1 − 60 Da) cross‐ring cleavage ions, respectively, fixing the location of feruloyl group at the O‐6 of the galactose residue. Copyright © 2004 John Wiley & Sons, Ltd.