Structure identification of a new immunostimulating polysaccharide from the stems of Dendrobium huoshanense

The water-soluble polysaccharide HPS, obtained from the stems of Dendrobium huoshanense by hot-water (50–60 °C) extraction and ethanol precipitation, was fractionated by DEAE–Cellulose anion-exchange and gel filtration chromatography including Sephacryl S-200 and Sephadex G-75/G-100, giving one polysaccharide fraction of HPS-1B23 which was investigated by chemical techniques and NMR spectroscopy. This polysaccharide fraction consists of glucose, mannose and galactose in the ratio of 31:10:8. On the basis of periodate oxidation–smith degradation, methylation analysis and partial acid hydrolysis, the repeating unit of HPS-1B23 was established: Pharmaceutical experiments showed that the polysaccharide of HPS-1B23 possessed potent stimulating functions on IFN-γ and TNF-α production in the culture medium of splenocytes and macrophages, respectively.