海带和马尾藻中褐藻胶的糖醛酸组成与序列结构的研究

STUDIES ON THE COMPOSITIONS AND SEQUENTIAL STRU-CTURES OF URONATE RESIDUES IN ALGINATES FROM CHINESE BROWN ALGAE LAMINARIA AND SARGASSUM

从中国产海带和3种马尾藻中提取褐藻胶,用IR谱分析其褐藻酸的结构特征,用高分辨~1H-NMR(400MHz)测定无损褐藻酸钠的单体组成和序列结构。IR谱表明了这4种褐藻酸单体组成的差异性。NMR谱的结果表明:海带、海蒿子、海黍子和鼠尾藻中褐藻胶的G组分摩尔分数F_G依次为0.35,0.40,0.45和0.44,而相应的GG二聚重复单元摩尔分数F_(GG)分别为0.21,0.37,0.36和0.34,即海带的F_(GG)明显小于三种马尾藻。文中引入一嵌段分布参数η=F_(MG)/(F_M·F_G),相应的η值依次为0.62,0.13,0.36和0.41,这表明了序列分布的差异性。

Sodium alginates and alginic acids were extracted from four Chinese brown algae. The alg-inic acids were characterized by infrared spectra. The compositions and sequential structures of uronate residues in the intact sodium alginates were determined by high-resolution 1H-NMR spectra (400 MHz). Results obtained may be summarized as follows:The infrared spectra of alginic acids at 808cm-1 and 787cm-1 show the difference in mono-meric compositions of alginates.The order of the Fe values (the molar fraction of guluronic acid) is: L. japonica (0.35) < S. pallidum (0.40)<S. thunbergii (0.44)<S. kjellmanianum (0.45), and the order of the FGG values (the diad frequencies of GC) is: L. japonica (0.21) <S. thunbergii (0.34)<S. kjellmanianum (0.36)<S. pallidum (0.37). This may indicate that one of the three species of Sargassum has a higher G content and more GG-sequences in alginates than Laminaria. Consequently Sargassum mentioned above would be good raw materials for the preparation of high gel strength alginates.The sequence distributions of uronate residues in alginates may be illustrative to use a parameter defined by η= FMG/(FM·FG). The order of η values is: L. japonica (0.62) > S. thunbergii (0.41) >S. kjellmanianum (0.36)>S. pallidum (0.13). This probably means that there is a marked difference in compositions and sequences of uronate residues in the alginates between Laminaria and Sargassum.