Structural characterisation of a water-soluble polysaccharide from tissue-cultured <i>Dendrobium huoshanense</i> C.Z. Tang et S.J. Cheng

<p>A water-soluble polysaccharide TC-DHPA4 with a molecular weight of 8.0 × 10⁵ Da was isolated from tissue-cultured <i>Dendrobium huoshanense</i> by anion exchange and gel permeation chromatography. Monosaccharide analysis revealed that the homogeneous polysaccharide was made up of rhamnose, arabinose, mannose, glucose, galactose and glucuronic acid with a molar ratio of 1.28:1:1.67:4.71:10.43:1.42. The sugar residue sequence analysis based on the GC-MS files and NMR spectra indicated that the backbone of TC-DHPA4 consisted of the repeated units:→6)-<i>β</i>-Galp-(1→6)-<i>β</i>-Galp-(1→4)-<i>β</i>-GlcpA-(1→6)-<i>β</i>-Glcp-(1→6)-<i>β</i>-Glcp-(→. The sugar residue sequences <i>β</i>-Glcp-(1→)-<i>α</i>-Rhap-(1→3)-<i>β</i>-Galp-(1→, <i>β</i>-Glcp-(1→4)-<i>α</i>-Rhap-(1→3)-<i>β</i>-Galp-(1→, <i>β</i>-Galp-(1→6)-<i>β</i>-Manp-(1→3)-<i>β</i>-Galp-(1→, and <i>α</i>-l-Araf-(1→2)-<i>β</i>-Manp-(1→3)-<i>β</i>-Galp-(1→ were identified as the branches attached to the C-3 position of (1→6)-linked galactose in the backbone.</p