Department of Food Chemistry and Phytochemistry, Institute of Applied Biosciences, Karlsruhe Institute of Technology (KIT) , Adenauerring 20a, 76131 Karlsruhe, Germany.
J Agric Food Chem. 2015 Jan 21;63(2):707-15. doi: 10.1021/jf505283x. Epub 2015 Jan 12.
Amaranth is a pseudocereal of high nutritional value, including a high dietary fiber content. Amaranth dietary fiber was suggested to contain large amounts of neutral rhamnogalacturonan I side chains. In this study, endo-arabinanase and endo-galactanase were used to liberate arabinan and galactan oligosaccharides from amaranth fiber. The liberated oligosaccharides were identified by high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) and HPLC-MS(n) using standard compounds, which were isolated from amaranth, sugar beet, potato, and red clover sprouts and characterized by one- and two-dimensional NMR spectroscopy. It was demonstrated that insoluble amaranth arabinans have linear and branched areas, with the O-3 position being the dominant branching point. Minor amounts of branches at position O-2 and double substitution were also found. Amaranth arabinans were also demonstrated to contain terminal α-(1→5)-linked l-arabinopyranose units. In addition, it was evidenced that galactans from amaranth seeds are composed of β-(1→4)-linked d-galactopyranose units, which can also be terminated with l-arabinopyranose units. In direct comparison to structural elucidation of amaranth fiber by using methylation analysis, the advantage of the enzymatic approach over methylation analysis was demonstrated.
苋菜籽是一种具有高营养价值的假谷物，含有丰富的膳食纤维。有研究表明，苋菜籽膳食纤维含有大量中性鼠李半乳糖醛酸 I 侧链。本研究采用内切阿拉伯聚糖酶和内切半乳聚糖酶从苋菜籽纤维中释放阿拉伯聚糖和半乳聚糖低聚糖。采用高效阴离子交换色谱-脉冲安培检测（HPAEC-PAD）和 HPLC-MS(n) 结合标准化合物对释放的低聚糖进行鉴定，这些标准化合物是从苋菜籽、糖甜菜、土豆和红三叶草芽中分离出来的，并通过一维和二维 NMR 光谱进行了表征。结果表明，不溶性苋菜籽阿拉伯聚糖具有线性和支化区域，O-3 位是主要的支化点。在 O-2 位和双取代位置也发现了少量的支链。还证明了苋菜籽阿拉伯聚糖含有末端α-(1→5)-连接的 l-阿拉伯吡喃糖单元。此外，证据表明，苋菜籽种子中的半乳糖主要由β-(1→4)-连接的 d-半乳糖吡喃糖单元组成，也可以被 l-阿拉伯吡喃糖单元终止。与使用甲基化分析对苋菜籽纤维的结构进行直接比较，证明了酶法优于甲基化分析。
