Isolation and Characterization of Alginate from Hizikia fusiformis and Preparation of its Oligosaccharides

Abstract

In this study, alginate was isolated from the residues of Hizikia fusiformis, after extraction of the fu- coidan. The yield, total carbohydrate, uronic acid, ash and moisture of alginate was 2.6% (based on wet mate- rial), 85.2, 80.5, 12.1 and 2.2%, respectively. The molecular mass of alginate was calculated to be about 7.0× 104 .The 1 H- and 13 C-NMR and IR spectra of alginate from H. fusiformis were in agreement with those of standard alginate. From the integral of the anomeric proton signals of D-mannuronic (M) and L-guluronic (G) acid residues in the 1 H-NMR spectrum, the molar ratio of both residues was calculated to be M: G＝0.53: 1. Eight alginate oligosaccharides were also isolated by gel permeation chromatography after using commercially available enzymes and were characterized by 2 D NMR techniques and ESI-MS spectrometry as ⊿(4-deoxy- L-erythro-hex-4-enopyranosyluronate) GGGG, ⊿GGG, ⊿GG, ⊿G, ⊿MMMM, ⊿MMM, ⊿MM and ⊿M. 沖縄産ヒジキのフコイダン抽出残渣からアルギン酸を分離・同定し，その化学特性を明らかにした．また，得られたアルギン酸を市販の酵素を用いて分解し，ゲルろ過クロマトグラフィーでオリゴ糖を分離してそれらの化学特性についても調べた．アルギン酸の全糖，ウロン酸，灰分および水分はそれぞれ85.2，80.5，12.1および2.2%であった．分子量は約7×10＾4と算出された．旋光およびIRスペクトルは標準アルギン酸とよく一致した．13C-および1H-NMRスペクトルの結果からL-グルロン酸とD-マンヌロン酸を同定し，アノメリックプロトンの積分結果からM/Gは0.53であった．さらに，得られたアルギン酸を市販の酵素を用いて分解し，ゲルろ過クロマトグラフィーで8種のオリゴ糖を分離した．2D-NMRおよびESI-MSスペクトルから，これらオリゴ糖はΔGGGG，ΔGGG，ΔGG，ΔG，ΔMMMM，ΔMMM，ΔMMおよびΔMと同定した．