Structural characterization and conformational properties of a polysaccharide isolated from Dendrobium nobile Lindl.

A water-soluble polysaccharide (JCP-40) from Dendrobium nobile Lindl. was extracted and purified. It was demonstrated as a single symmetrical peak based on HPSEC analysis and had an average molecular weight of 67.5 kDa. Combined with monosaccharide composition analysis, methylation analysis, 1D/2D NMR spectroscopy, the structural features of JCP-40 was proposed as follows: the major sugar residues of JCP-40 consisted of →4)-β-ᴅ-Manp-(1→ and →4)-β-ᴅ-Glcp-(1 → . Acetyl groups were found attached to the O-2 or O-3 positions on mannosyl residues based on NMR spectrum results. Rotational isomeric state (RIS)-Metropolis Monte Carlo method indicated that repeating unit increased from 30 to 120, the influence of Mw in this range affected chain flexibility. The conformational parameters (derived from Rg vs Mw and [η] vs Mw) from HPSEC suggested a random coil conformation for JCP-40.