黑小麦麦麸戊聚糖的部分酸水解特征与甲基化分析

研究了黑小麦麦麸戊聚糖(AEPH)的部分酸水解特征及其糖链的取代度和取代方式等结构信息. 分别采用0.02, 0.1和0.2 mol/L的三氟乙酸(Trifluoroacetic acid, TFA)对AEPH进行部分酸水解, 结合甲基化分析、 GC-MS和HPLC等方法对AEPH的糖链结构和相对分子质量分布进行了分析. 结果表明, 戊聚糖AEPH的糖残基主要由阿拉伯糖(Araf)和木糖(Xylp)组成. 其取代度(A/X), 即Araf与Xylp的比值为0.60, 并具有较高的相对分子质量(M_w=3.81×10⁵). AEPH的主链由Xylp残基通过1→4连接形成木聚糖. 主链Xylp在O2, O3或O2/O3位被Araf单取代或双取代. 非取代(u)、 单取代(m)和双取代(d)Xylp残基的组成比例为57.7∶22.0∶6.2. 非取代与取代Xylp的比值为2.1, 双取代与单取代Xylp比值(d/m)为0.3. Araf主要以非还原性末端T-Araf以及通过1→2和1→5连接形成低聚阿拉伯糖的形式与主链Xylp相连, 或与T-Xylp相连形成戊聚糖分子的支链.

Partial Acid Hydrolytic Characteristics and Methylation Analysis of Pentosans from Black-grained Wheat Bran

The hydrolytic characteristics and the structural features of substitute degree as well as substitute patterns of pentosans(AEPH) from black-grained wheat bran were analyzed.AEPH was hydrolyzed with 0.02,0.1,and 0.2 mol/L trifluoroacetic acid(TFA),respectively.The structural features and M w of AEPH were studied with methylation methods,combined with GC-MS and HPLC instruments.The results indicated that the residues of sugar constituents were mainly Araf and Xylp,with an Ara/Xyl(A/X) ratio of 0.60 and a high average molecular weight(M w) of 3.81×105.AEPH contained a xylan backbone of 1→4 linked Xylp residues which was mono- or disubstituted with Araf groups at position O3,O2 or at both O2 and O3 positions.The relative composition ratio of un-,mono-,and di-substituted Xylp in the arabinoxylan fraction was 57.7∶22.0∶6.2,with a high proportion of unsubstituted to substituted Xylp(2.1),and a very low proportion of di- to monosubstituted Xylp residues(d/m,0.3).Araf side groups were linked to Xylp residues of the backbone as terminal Araf single units.Moreover,small quantities of 1→2,and 1→5 linked Araf indicated the presence of short arabinan side chains terminated with T-Xylp residues.