Structural characterization and immunostimulatory activity of a novel linear α-(1 → 6)-D-glucan isolated from Panax ginseng C. A. Meyer

Panax ginseng C. A. Meyer is a well-known plant medicine in the world. Ginseng polysaccharides mainly contain starch-like glucan and pectin. In this paper, a novel glucan WGPA-UH-N1 was purified from ginseng pectin by the treatment of de-esterification and endo-polygalacturonase, followed by the chromatographies on DEAE-Sepharose Fast Flow and Sephadex G-50 column. WGPA-UH-N1 has molecular weight about 17 kDa. WGPA-UH-N1 was determined to be a linear α-(1 → 6)-D-glucan without side chains by FT-IR, 13 C-NMR, 1 H-NMR, HMQC and HMBC spectra. It is the first time to isolate a linear α-(1 → 6)-D-glucan from Panax ginseng C. A. Meyer. Immunological activity assays showed that WGPA-UH-N1, although not effective on the phagocytosis of macrophage, could significantly induce lymphocyte proliferation without mitogenic stimuli at 1.0 mg/mL or with LPS at 0.5 mg/mL, also significantly increase NO production at the range of 0.1–1.0 mg/mL in a dose-dependent manner. The immunological activities of WGPA-UH-N1 are different from those of the β-(1 → 6)-D-glucan (BIWP2) isolated from the fruit bodies of Bulgaria Inquinans (Fries).