Characterization of acetylated 4-O-methylglucuronoxylan isolated from aspen employing 1H and 13C NMR spectroscopy

被引:295
作者
Teleman, A
Lundqvist, J
Tjerneld, F
Stålbrand, H
Dahlman, O
机构
[1] STFI, Swedish Pulp & Paper Res Inst, SE-11486 Stockholm, Sweden
[2] Univ Lund, Dept Biochem, SE-22100 Lund, Sweden
关键词
aspen wood (Populus tremula); hemicellulose; extraction; xylan; structure; O-acetylation; microwave oven; fractionation;
D O I
10.1016/S0008-6215(00)00249-4
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Water-soluble hemicelluloses were extracted from milled aspen wood (Populus tremula) employing microwave oven treatment at 180 degreesC 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 H-1 and C-13 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-xyIopyranosyl structural elements: unsubstituted (50 mol%), 2-O-acetylated (13 mol%), 3-O-acetylated (21 mol%), 2,3-di-O-acetylated (6 mol%) and [MeGIcA 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. (C) 2000 Elsevier Science Ltd. All rights reserved.
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页码:807 / 815
页数:9
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