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Study on Dendrobium officinale O-acetyl-glucomannan (Dendronan®): Part I. Extraction, purification, and partial structural characterization

Xing, X., Cui, S.W., Nie, S., Phillips, G.O., Goff, H.D., Wang, Q. (2014). Study on Dendrobium officinale O-acetyl-glucomannan (Dendronan®): Part I. Extraction, purification, and partial structural characterization, 4(1), 74-83. http://dx.doi.org/10.1016/j.bcdf.2014.06.004

Abstract

It is believed that some polysaccharides with specific structures may play important roles in the medicinal properties of Dendrobium plants. In the current study, a crude polysaccharide preparation, containing 71.4% non-starch polysaccharide and 17.1% starch, was obtained from Dendrobium officinale herbal materials using sequential hot water extractions. A polysaccharide fraction, with a Mw of 312 kDa, was isolated by subjecting the crude polysaccharide to sequential treatments of thermo-stable α-amylase, multiple freeze-thaw processes, dialysis, ethanol precipitation (3 volumes), and freeze-drying. The purified polysaccharide was free of starch and with a purity of 90.4%. The analysis of monosaccharide compositions showed that the purified polysaccharide consisted dominantly of mannose and glucose, in a molar ratio of 6.9:1. Methylation analysis indicated that the glucomannan was a linear polymer without any branches. Both FT-IR and NMR spectroscopic analyses suggested that the glucomannan was O-acetylated and was primarily composed of β-1,4-d- mannopyranosyl and β-1,4-d-glucopyranosyl residues. Acetyl groups were found attached to the O-2 or O-3 positions on some mannosyl residues based on 1D 1H NMR, 2D 1H-1H TOCSY, and 2D 1H-1H COSY spectra. In conclusion, the major polysaccharide from Dendrobium officinale is an O-acetylated glucomannan. © 2014 Published by Elsevier Ltd.

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