Fragmentation pattern of underivatised xylo-oligosaccharides and their alditol derivatives by electrospray tandem mass spectrometry

Maltopentaose and olive pulp xylo-oligosaccharides and the correspondent alditol derivatives were analysed by ESI-MS and ESI-MS/MS. The ESI-MS spectrum of maltopentaose and maltopentaose alditols showed M+Na]⁺and M+H]⁺ ions. ESI-MS spectrum of xylo-oligosaccharides and their alditols showed M+Na]⁺of neutral (Xyl_3–6) and acidic (Xyl_2–3MeGlcA and Xyl_2–3GlcA) xylo-oligosaccharides. The ESI-MS/MS spectra of maltopentaose and underivatised xylo-oligosaccharides presented fragments of glycosidic cleavages attributed to B/Z and C/Y ions. On the other hand, MS/MS spectra of the correspondent alditols showed glycosidic cleavages unambiguously identified as B-type and Y-type ions. Y-type fragment ions showed higher abundance in the MS/MS spectra of the alditol derivatives when compared to the non-reduced samples. The study of the oligoxylosyl alditols fragmentation permits to distinguish fragmentation pathways that occur both from the reducing end and from the non-reducing end of the xylan chain, allowing to obtain more information about the localization of the acidic substituent along the glucuronoxylan backbone.