Evtuguin Dmitry V, Tomás Jorge L, Silva Artur M S, Neto Carlos Pascoal
CICECO and Department of Chemistry, University of Aveiro, P 3810-193, Aveiro, Portugal.
Carbohydr Res. 2003 Mar 28;338(7):597-604. doi: 10.1016/s0008-6215(02)00529-3.
A heteroxylan was isolated from Eucalyptus globulus wood by extraction of peracetic acid delignified holocellulose with dimethyl sulfoxide. Besides (1-->4)-linked beta-D-xylopyranosyl units of the backbone and short side chains of terminal (1-->2)-linked 4-O-methyl-alpha-D-glucuronosyl residues (MeGlcA) in a 1:10 molar ratio, this hemicellulose contained galactosyl and glucosyl units attached at O-2 of MeGlcA originating from rhamnoarabinogalactan and glucan backbones, respectively. About 30% of MeGlcA units were branched at O-2. The O-acetyl-(4-O-methylglucurono)xylan showed an acetylation degree of 0.61, as determined by 1H NMR spectroscopy, and a weight-average molecular weight (M(w)) of about 36 kDa (P=1.05) as revealed from size-exclusion chromatography (SEC) analysis. About half of the beta-D-xylopyranosyl units of the backbone were found as acetylated moieties at O-3 (34 mol%), O-2 (15 mol%) or O-2,3 (6 mol%). Practically, all beta-D-xylopyranosyl units linked at O-2 with MeGlcA residues were 3-O-acetylated (10 mol%).
通过用二甲基亚砜萃取过氧乙酸脱木质素全纤维素，从蓝桉木材中分离出一种杂木聚糖。除了主链中（1→4）连接的β-D-吡喃木糖基单元和末端（1→2）连接的4-O-甲基-α-D-葡糖醛酸残基（MeGlcA）以1:10摩尔比存在的短侧链外，这种半纤维素还含有分别连接在源自鼠李阿拉伯半乳聚糖和葡聚糖主链的MeGlcA的O-2位上的半乳糖基和葡萄糖基单元。约30%的MeGlcA单元在O-2位有分支。通过1H NMR光谱测定，O-乙酰基-（4-O-甲基葡糖醛酸）木聚糖的乙酰化度为0.61，尺寸排阻色谱（SEC）分析显示其重均分子量（M(w)）约为36 kDa（P = 1.05）。主链中约一半的β-D-吡喃木糖基单元在O-3（34 mol%）、O-2（15 mol%）或O-2,3（6 mol%）位被乙酰化。实际上，所有在O-2位与MeGlcA残基相连的β-D-吡喃木糖基单元都在3-O位被乙酰化（10 mol%）。
