STRUCTURAL CHARACTERIZATION AND ANTI-GLYCATION ACTIVITYIN VITROOF A WATER-SOLUBLE POLYSACCHARIDE FROMDENDROBIUM HUOSHANENSE

Abstract

A water-soluble polysaccharide with anti-glycation activity, designated as DHP-W2, was isolated and purified from the fresh stems of Dendrobium huoshanense. DHP-W2 mainly consisted of glucose, xylose, galactose and trace of galacturonic acid, and its average molecular weight was approximately 73 kDa. Methylation analysis and one- and two-dimensional nuclear magnetic resonance (NMR) spectroscopy, including 1H-NMR, 13C-NMR, 1H-1H correlation spectroscopy, heteronuclear single quantum correlation spectroscopy and heteronuclear multiple-bond correlation spectroscopy, revealed that the repeating units of DHP-W2 had a backbone consisting of 1,6-linked β-D-Glcp, 1,4-linked β-D-Glcp and 1,4,6-linked β-D-Glcp with branches at O-4/6. Sugar residues of branches were 1,2,4-linked α-D-Xylp, 1,4-linked α-D-Xylp, 1-linked α-D-Xylp, 1-linked α-D-Galp and 1-linked α-D-GalpA. Preliminary experiment in vitro indicated that DHP-W2 had an anti-glycation activity with dose- and time-dependent effects. PRACTICAL APPLICATIONS Because of potential biological and pharmacological functions, polysaccharides from edible and medicinal plants have gained special attention in the food industry. Dendrobium huoshanense C. Z. Tang and S. J. Cheng, 1984, which is a well-known edible and medicinal plant belonging to Orchidaceae family, has been used as a tonic to prevent cataractogenesis, throat inflammation and chronic superficial gastritis for centuries in China. This paper reports the structure features of a homogeneous polysaccharide obtained from D. huoshanense and its anti-glycation activity by a combination of chemical, instrumental and biochemical analysis approaches, including gas chromatography–mass spectrometry (GC-MS), methylation analysis, Fourier transform infrared, one- and two-dimensional nuclear magnetic resonance spectroscopy, and fluorescence spectrophotometry. The paper's purpose was to provide structural information not only for further elucidation of the relationship between structure and function but also for better understanding of pharmacological mechanism of D. huoshanense polysaccharides. It can be expected to develop the functions of the polysaccharides from D. huoshanense in food industries.