Structural studies of a heteroxylan from Plantago major L. seeds by partial hydrolysis, HPAEC-PAD, methylation and GC–MS, ESMS and ESMS/MS

The seed mucilage from Plantago major L. contains acidic heteroxylan polysaccharides. For further structural analysis, oligosaccharides were generated by partial acid hydrolysis and then isolated by high-pH anion-exchange chromatography (HPAEC). Each HPAEC fraction was shown by ESMS to contain one major oligosaccharide and several minor components. Partial structures of the oligosaccharides were determined using GC–MS, ESMS and ES tandem mass spectrometry (ESMS/MS). A (1→4)-linked xylan trisaccharide and (1→3)-linked xylan oligosaccharides with DP 6–11 suggested that the backbone of the heteroxylan polysaccharide consisted of blocks of (1→4)-linked and (1→3)-linked Xylp residues. A (1→2)-linked Xylp disaccharide and a branched tetrasaccharide were also found, revealing that single Xylp residues are linked to the O-2 of some of the (1→4)-linked Xylp residues in the backbone. In addition, our results confirm the presence of side chains consisting of the disaccharide GlcpA-(1→3)-Araf.