title: Structural studies of an arabinan from the stems of Ephedra sinica by methylation analysis and 1D and 2D NMR spectroscopy.
abstract: Plant arabinan has important biological activity. In this study, a water-soluble arabinan (Mw∼6.15kDa) isolated from the stems of Ephedra sinica was found to consist of (1→5)-Araƒ, (1→3,5)-Araƒ, T-Araƒ, (1→3)-Araƒ and (1→2,5)-Araƒ residues at proportions of 10:2:3:2:1. A tentative structure was proposed by methylation analysis, nuclear magnetic resonance (NMR) spectroscopy ((1)H NMR, (13)C NMR, DEPT-135, (1)H-(1)H COSY, HSQC, HMBC and ROESY) and literature. The structure proposed includes a branched (1→5)-α-Araf backbone where branching occurs at the O-2 and O-3 positions of the residues with 7.7% and 15.4% of the 1,5-linked α-Araf substituted at the O-2 and O-3 positions. The presence of a branched structure was further observed by atomic force microscopy. This polymer was characterized as having a much longer linear (1→5)-α-Araf backbone as a repeating unit. In particular, the presence of α-Araf→3)-α-Araf-(1→3)-α-Araf-(1→ attached at the O-2 is a new finding. This study may facilitate a deeper understanding of structure-activity relationships of biological polysaccharides from the stems of E. sinica.
authors: Key Laboratory of Chinese Materia Medica (Heilongjiang University of Chinese Medicine), Ministry of Education, Harbin 150040, PR China.
authors: Yong-Gang
authors: YG
authors: Xia
authors: Key Laboratory of Chinese Materia Medica (Heilongjiang University of Chinese Medicine), Ministry of Education, Harbin 150040, PR China.
authors: Jun
authors: J
authors: Liang
authors: Key Laboratory of Chinese Materia Medica (Heilongjiang University of Chinese Medicine), Ministry of Education, Harbin 150040, PR China.
authors: Bing-You
authors: BY
authors: Yang
authors: Key Laboratory of Chinese Materia Medica (Heilongjiang University of Chinese Medicine), Ministry of Education, Harbin 150040, PR China.
authors: Qiu-Hong
authors: QH
authors: Wang
authors: Key Laboratory of Chinese Materia Medica (Heilongjiang University of Chinese Medicine), Ministry of Education, Harbin 150040, PR China. Electronic address: hxkuang@hotmail.com.
authors: Hai-Xue
authors: HX
authors: Kuang
mesh_terms: D029790:Ephedra sinica / Q000737:chemistry*; D008745:Methylation; D018547:Plant Stems / Q000737:chemistry; D011134:Polysaccharides / Q000737:chemistry*
chemical_list: D011134:Polysaccharides; C030080:araban
keywords: Arabinan; Ephedra sinica; NMR; Structural elucidation