Characterization of acetylated 4-O-methylglucuronoxylan isolated from aspen employing 1H and 13C NMR spectroscopy.
Water-soluble hemicelluloses were extracted from milled aspen wood (Populus tremula) employing microwave oven treatment at 180 degrees C 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-alpha-D-GlcpA-(1-->2)][3-O-Ac]-beta-D-Xylp-(1 --> could also be identified. On the average, these two xylans were composed of the following (1-->4)-linked beta-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 alpha-(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.
Teleman
A
A
Swedish Pulp and Paper Research Institute, STFI, Stockholm, Sweden. anita.teleman@stfi.se
Lundqvist
J
J
Tjerneld
F
F
Stålbrand
H
H
Dahlman
O
O
D000107:Acetylation; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002473:Cell Wall / Q000737:chemistry; D002845:Chromatography; D009682:Magnetic Resonance Spectroscopy; D008872:Microwaves; D008969:Molecular Sequence Data; D011134:Polysaccharides / Q000737:chemistry* / Q000302:isolation & purification*; D019685:Rosales / Q000737:chemistry; D014934:Wood; D014990:Xylans / Q000737:chemistry* / Q000302:isolation & purification*
D011134:Polysaccharides; D014990:Xylans; C007916:hemicellulose