Structural characterization of a 2- O-acetylglucomannan from Dendrobium officinale stem

Abstract

A heteropolysaccharide obtained from an aqueous extract of dried stem of Dendrobium officinale Kimura and Migo by anion-exchange chromatography and gel-permeation chromatography, was investigated by chemical techniques and NMR spectroscopy, and is demonstrated to be a 2- O-acetylglucomannan, composed of mannose, glucose, and arabinose in 40.2:8.4:1 molar ratios. It has a backbone of (1 → 4)-linked β- d-mannopyranosyl residues and β- d-glucopyranosyl residues, with branches at O-6 consisting of terminal and (1 → 3)-linked Man p, (1 → 3)-linked Glc p, and a small proportion of arabinofuranosyl residues at the terminal position. The acetyl groups are substituted at O-2 of (1 → 4)-linked Man p and Glc p. The main repeating unit of the polysaccharides is reported.