Structure and bioactivity of a polysaccharide extracted from protocorm-like bodies of Dendrobium huoshanense

The crude polysaccharides of Dendrobium huoshanertse were fractionated by anion-exchange chromatography and gel permeation chromatography, giving one homogeneous fraction DHP-4A with molecular weight of 2.32 x 10(5) Da. UV spectrum indicated that there was no existence of proteins and nucleic acids in DHP-4A. Monosaccharide analysis revealed that DHP-4A was made up of glucose, arabinose, mannose and rhamnose with a molar ratio of 13.8:3.0:6.1:2.1. The backbone of DHP-4A consisted of (1 -> 6)-linked glucose, (1 -> 6)-linked mannose and (1 -> 3,6)-linked mannose. The beta-L-Rhap-(1 -> 2)-beta -L-Rhap-(1 -> 4)-beta-D-Manp-(1 -> and alpha-L-Araf-(1 -> 3)- alpha-L-Araf -(1 -> 3)- alpha-L-Araf-(1 -> were regarded as the branches attached to the C-3 position of (1 -> 6)-linked mannose in the backbone. The sugar residue sequence was further determined by NMR spectra including H-1 NMR,C-13 NMR, HSQC and HMBC. Pharmacological tests showed that DHP-4A can significantly stimulate RAW 264.7 macrophage cells to secrete NO, TNF-alpha, IL-6 and IL-10 via activation of p38, ERK, JNK and translocation of nuclear NF-kappa B, indicating this polysaccharide possesses good immunoregulatory activity. (C) 2014 Elsevier B.V. All rights reserved.