Application of nano-probe NMR for structure determination of low nanomole amounts of arabinoxylan oligosaccharides fractionated by analytical HPAEC-PAD Original Research Article

A methodology for NMR analysis of low nanomole amounts of oligosaccharides fractionated by analytical HPAEC is presented. Arabinoxylan derived oligosaccharides purified by HPAEC-PAD on an analytical column, by single injections, were analyzed with nano-probe NMR and MALDI-TOF MS to provide full structural assignment. The NMR data were obtained with a 500 MHz NMR spectrometer equipped with a 1H-observe nano-probe. Both one- and two-dimensional experiments on arabinoxylan samples in the low nanomole range were performed, including 1H–1H DQF-COSY, 1H–1H TOCSY and 1H–1H ROESY. These experiments allowed, in combination with MALDI-TOF MS and literature NMR data, a complete structural determination of several tetra-, penta-, hexa- and heptasaccharides. Two new structures: α-l-Araf-(1→2)-β-d-Xylp-(1→4)-β-d-Xylp-(1→4)-β-d-Xylp-(1→4)-d-Xylp and α-l-Araf-(1→2)[α-l-Araf-(1→3)]-β-d-Xylp-(1→4)-β-d-Xylp-(1→4)-β-d-Xylp-(1→4)-d-Xylp) were characterized, as well as some previously published structures.