Characterization of acetylated 4-O-methylglucuronoxylan isolated from aspen employing 1H and 13C NMR spectroscopy
Publikation/Tidskrift/Serie: Carbohydrate Research
Water-soluble hemicelluloses were extracted from milled aspen wood (Populus tremula) employing microwave oven treatment at 180oC for 10 min. The final pH of this extract was 3.5. From this extract oligo- and polysaccharides were isolated and subsequently fractionated by size-exclusion chromatography. The structures of the saccharides in three of the fractions obtained were determined by 1H and 13C NMR spectroscopy, using homonuclear and heteronuclear two-dimensional techniques. The polysaccharides present in the two fractions eluted first were O-acetyl-(4-O-methylglucurono)xylans. The average degree of acetylation of the xylose residues in these compounds was 0.6. The structural element ->4)[4-O-Me-α-d-GlcpA-(1->2)][3-O-Ac]-β-d-Xylp-(1-> could also be identified. On the average, these two xylans were composed of the following (1->4)-linked β-d-xylopyranosyl structural elements: unsubstituted (50 mol%), 2-O-acetylated (13 mol%), 3-O-acetylated (21 mol%), 2,3-di-O-acetylated (6 mol%) and [MeGlcA α-(1->2)][3-O-acetylated] (10 mol%). Most of the 4-O-methylglucuronyl and acetyl substituents in the isolated polysaccharides survived the microwave oven treatment. The third fraction, eluted last, contained acetylated xylo-oligosaccharides, with minor contamination by an acetylated mannan. In the case of these xylo-oligosaccharides, the average degree of acetylation was 0.3.
- Aspen wood (Populus tremula)
- Microwave oven
- ISSN: 0008-6215