Thude Sebastian, Classen Birgit
Institute of Pharmacy, Department of Pharmaceutical Biology, University of Kiel, Gutenbergstr. 76, D-24118 Kiel, Germany.
Phytochemistry. 2005 May;66(9):1026-32. doi: 10.1016/j.phytochem.2005.02.028.
This investigation shows structural features of two macromolecules from roots of Echinacea pallida (Nutt.) Nutt: an arabinogalactan-protein (AGP) and an arabinan. The arabinogalactan-protein was precipitated with beta-glucosyl Yariv reagent from a high molecular weight fraction. Investigations of the neutral sugar composition revealed Gal (52.1% w/w) and Ara (38.2% w/w) in a ratio of 1.4:1, accompanied by Glc (6.9% w/w) and Rha (2.8% w/w). The content of uronic acids was 6.2%. Mild acid hydrolysis detects Ara and Glc being located at the periphery of the molecule. Linkage analyses and NMR spectroscopy revealed a backbone of the polysaccharide mainly consisting of 3-linked and 3,6-linked Galp-residues. Side chains are composed of 3,6-linked or 6-linked Galp terminating in 5-linked Araf, terminal Araf, Glcp and GlcAp. The protein part (3.9% w/w) of the AGP is rich in Hyp, Ser, Ala, Thr, Glu, Asp and Gly. The amount of Hyp was determined by a colorimetric method and found to be (0.65% (w/w) of the AGP, which is in good agreement with the result obtained by amino acid hydrolysis (0.67% w/w). The arabinan was isolated from the supernatant of the Yariv precipitation on the basis of solubility in EtOH (80%). It mainly consists of Ara (85.8%). Linkage analyses and NMR spectroscopy indicate a highly branched molecule, consisting of 3,5-linked, 5-linked and terminal Araf-residues in equal amounts.
本研究揭示了淡紫松果菊（Echinacea pallida (Nutt.) Nutt）根中两种大分子的结构特征：一种阿拉伯半乳聚糖蛋白（AGP）和一种阿拉伯聚糖。阿拉伯半乳聚糖蛋白是从高分子量级分中用β-葡萄糖基Yariv试剂沉淀出来的。对中性糖组成的研究表明，半乳糖（Gal，52.1% w/w）和阿拉伯糖（Ara，38.2% w/w）的比例为1.4:1，同时还有葡萄糖（Glc，6.9% w/w）和鼠李糖（Rha，2.8% w/w）。糖醛酸含量为6.2%。温和酸水解检测到阿拉伯糖和葡萄糖位于分子外围。键合分析和核磁共振光谱显示，多糖的主链主要由3-连接和3,6-连接的半乳糖残基组成。侧链由以5-连接的阿拉伯糖、末端阿拉伯糖、葡萄糖和葡萄糖醛酸结尾的3,6-连接或6-连接的半乳糖组成。AGP的蛋白质部分（3.9% w/w）富含羟脯氨酸（Hyp）、丝氨酸（Ser）、丙氨酸（Ala）、苏氨酸（Thr）、谷氨酸（Glu）、天冬氨酸（Asp）和甘氨酸（Gly）。羟脯氨酸的含量通过比色法测定，发现占AGP的0.65%（w/w），这与氨基酸水解得到的结果（0.67% w/w）非常一致。阿拉伯聚糖是根据其在80%乙醇中的溶解度从Yariv沉淀的上清液中分离出来的。它主要由阿拉伯糖（85.8%）组成。键合分析和核磁共振光谱表明这是一个高度分支的分子，由等量的3,5-连接、5-连接和末端阿拉伯糖残基组成。
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