Hama Y, Nakagawa H, Kurosawa M, Sumi T, Xia X, Yamaguchi K
Department of Applied Biological Sciences, Faculty of Agriculture, Saga University, Japan.
Anal Biochem. 1998 Dec 1;265(1):42-8. doi: 10.1006/abio.1998.2894.
This paper describes a new gas chromatographic method for the compositional analysis of algal galactans containing 3,6-anhydrogalactose, which is readily destroyed in usual acid hydrolysis and methanolysis. Mercaptolysis of galactans was carried out under an anhydrous condition using the newly developed solvent system, an ethanethiolic HCl solution which had been prepared by blowing dry HCl gas into ethanethiol. By heating galactans in 0.5 N HCl/ethanethiol at 60 degrees C for 12 h, component sugars including 3,6-anhydrogalactose were released quantitatively as their diethyl mercaptals. The monosaccharide diethyl mercaptals were trimethylsilylated and analyzed by gas-liquid chromatography. Each component monosaccharide was detected as a single peak since neither anomeric nor structural isomers can be produced by mercaptolysis. Furthermore, the solvent system was improved by the addition of methanol in a ratio (2/1, v/v) of ethanethiol to methanol. Heating of galactans at 60 degrees C in 0.5 N HCl/[ethanethiol:methanol (2/1, v/v)] released more rapidly and quantitatively monosaccharide diethyl mercaptals without any formation of monosaccharide methyl glycosides. The present method was applicable to not only algal galactans but also algal powders.
本文描述了一种用于分析含有3,6-脱水半乳糖的藻类半乳聚糖组成的新气相色谱方法，3,6-脱水半乳糖在常规酸水解和甲醇解中容易被破坏。半乳聚糖的巯基解反应在无水条件下使用新开发的溶剂体系进行，该溶剂体系是通过将干燥的HCl气体吹入乙硫醇中制备的乙硫醇HCl溶液。通过在60℃下将半乳聚糖在0.5N HCl/乙硫醇中加热12小时，包括3,6-脱水半乳糖在内的组成糖以其二乙硫醇缩醛的形式定量释放。单糖二乙硫醇缩醛进行三甲基硅烷化并通过气液色谱分析。由于巯基解反应不会产生端基异构体或结构异构体，因此每种单糖组分都作为一个单峰被检测到。此外，通过以乙硫醇与甲醇的比例（2/1，v/v）添加甲醇来改进溶剂体系。在0.5N HCl/[乙硫醇：甲醇（2/1，v/v）]中于60℃加热半乳聚糖，能更快且定量地释放单糖二乙硫醇缩醛，且不会形成任何单糖甲基糖苷。本方法不仅适用于藻类半乳聚糖，也适用于藻类粉末。
