Dervilly G, Saulnier L, Roger P, Thibault J
Unité de Recherche sur les Polysaccharides, leurs Organisations et Interactions, INRA, B.P. 71627, 44316 Nantes Cedex 03, France.
J Agric Food Chem. 2000 Feb;48(2):270-8. doi: 10.1021/jf990222k.
Water-soluble arabinoxylans from wheat flour were purified and fractionated by graded ethanol precipitation. Six fractions were obtained at 20% (F20), 30% (F30), 40% (F40), 50% (F50), 60% (F60), and 70% (F70) saturation with ethanol. Neutral sugars and (1)H NMR analyses revealed differences in structural characteristics. The Ara/Xyl ratio and the amount of Xylp residues disubstituted increased with ethanol concentration. Ferulic acid content was higher in fractions precipitated at low ethanol percentage. Fractions were refractionated by SEC, leading to 46 subfractions with low polydispersity index. Substitution degree was apparently linearly related to the amount of disubstituted Xylp. Macromolecular characteristics (M(w), [eta], R(G), q, nu) determined by multiangle laser light scattering and viscosimetry were similar among all fractions. A rather flexible conformation was determined for the arabinoxylans, in conflict with the admitted rodlike conformation. The substitution degree had no influence on the conformation or on the rigidity of the polymers. Evidence for the presence of ferulic acid dimers in the water-soluble arabinoxylans is provided, which probably explains the unexpected conformation and macromolecular characteristics.
从小麦粉中提取的水溶性阿拉伯木聚糖通过梯度乙醇沉淀法进行纯化和分级分离。在乙醇饱和度为20%（F20）、30%（F30）、40%（F40）、50%（F50）、60%（F60）和70%（F70）时获得了六个级分。中性糖和¹H NMR分析揭示了结构特征上的差异。随着乙醇浓度的增加，阿拉伯糖/木糖比例以及二取代木糖残基的数量增加。在低乙醇百分比下沉淀的级分中阿魏酸含量较高。通过尺寸排阻色谱法对级分进行再分级，得到了46个多分散指数较低的亚级分。取代度显然与二取代木糖的数量呈线性相关。通过多角度激光光散射和粘度测定法测定的所有级分的大分子特性（Mw、[η]、RG、q、ν）相似。确定阿拉伯木聚糖具有相当灵活的构象，这与公认的棒状构象相矛盾。取代度对聚合物的构象或刚性没有影响。提供了水溶性阿拉伯木聚糖中存在阿魏酸二聚体的证据，这可能解释了意外的构象和大分子特性。
