Tandem mass spectrometry of fucoidan-derived fragments, labeled with heavy-oxygen

A procedure for the partial depolymerization of sulfated fucans and selective labeling with O-18 was developed. A tandem electrospray ionization mass spectrometry (ESI MS/MS) was applied for the direct analysis of mixtures of structurally-different oligosaccharides, derived from the fucoidans of known structure. The presence of label allowed unambiguous distinguishing between the fragment ions of X-0,2(0)-type at m/z 287 and (2,4)A-type at m/z 285, since O-18 at the reducing end gave thor +2 mass shifting. Thus, ESI MS/MS was able to detect (1,2)-type of linkage in disaccharides from the fucoidan of brown alga S. cichorioides for the first time. It was also discovered that (2,4)A-type fragments in 4-linked disaccharides that were incorrectly assigned to X-0,X-2-type previously, suggested, probably, substitution at C-4 in mono- and disaccharide fragments, derived from the fucoidan of the brown alga F. evanescens. (C) 2017 Elsevier Ltd. All rights reserved.