改良ジエチルジチオアセタール化法による増粘多糖類構成糖の分析

摘要

The identification test for thickening polysaccharides containing neutral saccharides and uronic acids was investigated by GC analysis of constituent monosaccharides. The reported method, in which monosaccharides were converted to diethyldithioacetal derivatives with ethanethiol followed by trimethylsilylation, was improved in terms of operability and reproduci-bility of GC/MS analysis. The suitability of the improved diethyldithioacetal derivatization method was determined for seven thickening polysaccharides, I.e., carob bean gum, guar gum, karaya gum, gum arabic, gum ghatti, tragacanth gum and peach gum. The samples were acid-hydrolyzed to form monosaccharides. The hydrolysates were derivatized and analyzed with GC/FID. Each sugar derivative was detected as a single peak and was well separated from others on the chromatograms. The amounts of constituent monosaccharides in thickening polysaccharides were successfully estimated. Seven polysaccharides were distinguished from each other on the basis of constituent monosaccharides. Further examination of the time period of hydrolysis of polysaccharides using peach gum showed that the optimal times were not the same for all monosaccharides. A longer time was needed to hydrolyze glucuronic acid than neutral saccharides. The findings suggest that hydrolysis time may sometimes affect the analytical results on composition of constituent monosaccharides in polysaccharides.%ウロン酸含有増粘多糖類の構成糖組成比をGC分析する 方法を検討した．単糖にジエチルジチオアセタール化と TMS化を施してGC／MSで分析する既報の方法の反応ス ケールを5倍にし，さらに溶媒抽出を用いた調製法に変更 し，操作性と再現性を向上させた．多糖類7品目を加水分 解し，改良操作法により誘導体化してGC／FIDで分析し た・構成糖の誘導体をクロマトグラム上でいずれも単一の ピークとして検出し，互いに分離することができ，同定と 定量が可能であった．構成楯の種類と含量比から7品目を 区別することができた．さらに加水分解反応の最適化を試 みたところ，グルクロン酸は中性糖よりも加水分解に時間 がかかることが示された．品目間の識別は6時間の加水分 解で十分であるが，構成糖組成比の精密な比較を行う場合 には，構成糖ごとに加水分解時間の最適化を行う必要があ ると考えられた．