Isolation and structural characterization of a novel galactomannan from Eremurus anisopterus (Ker. et Kir) Regel roots

A novel galactomannan was obtained from the roots of Eremurus anisopterus (Ker. et Kir) Regel, an ephemeroid plant in the Gurbantunggut Desert in Xinjiang. The crude polysaccharide was extracted following the usual separation procedure, including water dissolution, centrifugation and precipitation with ethanol. The crude polysaccharide was then applied to anion-exchange chromatography and gel filtration to obtain a homogeneous polysaccharide E1. The average molecular weight of E1 was estimated to be 6 kDa according to the calibration curve. On the basis of composition analysis, methylation analysis, periodate oxidation analysis, Smith degradation, infrared spectra (IR) and nuclear magnetic resonance (NMR) experiments, E1 is a novel linear galactomannan with a main chain composed of (1 → 6)-linked α-d-Galp and (1 → 2)-α-d-Manp at a relative molar ratio of 1:3.