水杉木材半乳糖基-葡萄甘露聚糖的结构研究

<正>水杉木材约含40％纤维素、31％木质素和25％半纤素。从水杉木材制备的综纤维素中可分出两种不同的高聚糖:一种为水溶性半乳糖基-葡萄甘露聚糖;另一种为碱溶性半乳糖基-葡萄甘露聚糖。前一种比旋光度为-9.1°,DP_n为86,糖基比为0.48:1:2;后种比旋光度为-23.4°,DP_n为112,糖基比为0.1:1:2.4。这两种高聚糖都是线型分子,主链都是由β-D-吡喃型葡萄糖基和β-D-吡喃型甘露糖基通过1→4苷键连接而成的,α-D-吡喃型半乳糖基则以侧链形式通过1→6苷链连接主链甘露糖基的C-6上。 与一般针叶材相比,水杉木材中水溶性半乳糖基-葡萄甘露聚糖的半乳糖基和甘露糖基都偏低,而在碱溶性的半乳糖基-葡萄甘露聚糖中,则甘露糖基偏低。

STUDIES ON STRUCTURES OF THE GALACTOGLUCOMANNANS FROM METASEQUOIA GLYPTOSTROBOIDES

A galactoglucomannan (alkline soluble) and a galactoglucomannan (water soluble) were isolated from the holocellulose of the wood (metasequoia glyptostroboidcs) which contains 40% cellulose, 31% lignin, 25% hemicellulose. The former has Dpn 112, a]D-23.4?and, on hydrolysis, yields galactoss, glucose, mannose in themolar ratio of 0.1:1.0:2.4. The latter has DPn 86, a]D-9.1?and sugar ratio of 0.48:1.0:2.0. Each has a main chain of 1? linked D-mannopyranosyl and D-glucopyranosyl residues, but the latter has more D-galactopyranosyl residues attached to C-6 of D-mannopyranosyl.The structures of the mannans from Metasequoia glyptostroboidcs are similar to mannans found in other softwood, but there are differences in their sugar ratios.