MALDI-TOF-MS and HPAE-PAD-chromatographic analysis of xyloglucan oligosaccharides generated from <i>Brassica campestris</i> meal

Abstract

Hemicellulosic polysaccharides obtained from depectinated and delignified mus tard meal by extraction with 1<i>M</i> KOH(1OH-M) is fractionated by anion exchange chromatography yielding a neutral xylogluc an rich population (1OH-N). Thelatter fraction is further characterized by size exclusion chromatography, which resulted in one broad peak between Kav.0.3 0.7, corresponding to an apparent molecular weight of 90±30 kDa. Sugar compositional analysis and degradationstudies with spec ific enzymes were performed to obtain information about the s tructure. The results obtained show that thexyloglucan present in 1OH-N fraction contained a hepta (1)-, an octa (2)-, a nona (3)- and a deca (4)- sac charides as themajor building sub-units. The structures of these oligosaccharides were determined. Hydrolysis of 1OH-M fraction with endo-<img src='/image/spc_char/beta.gif' border=0> -(1 4)-D-xylanase and analysis of the xylan derived oligos accharides by chromatography and mass spectrometryshow that mustard meal xylan is composed of a <img src='/image/spc_char/beta.gif' border=0>-(1 4)-linked-D-xylopyranose backbone substituted with D-glucuronicacid residue and its 4- -methyl derivative.