Isolation, purification, and structural characterization of polysaccharides from Atractylodis Macrocephalae Rhizoma and their immunostimulatory activity in RAW264.7 cells.

Three water-soluble polysaccharides (AMAP-1, AMAP-2 and AMAP-3) were isolated and purified from Atractylodis Macrocephalae Rhizoma by using the combination of ion-exchange chromatography and gel permeation chromatography. The structures of the polysaccharides were characterized by chemical derivatization, HPGC, GC-MS, FT-IR, and NMR techniques. Structural analyses show that the three polysaccharides are pectin-type macromolecules consisting of homogalacturonan (HG) and rhamnogalacturonan type I (RG-I) regions in different ratios. Immunostimulatory assay highlighted that the RG-I-rich AMAP-1 and AMAP-2 with high molecular weights can stimulate RAW264.7 macrophages to release nitric oxide, but HG-rich AMAP-3 with a low molecular weight cannot. This finding suggests that the immune activity may be related to the side chains of the RG-I region, which provides a certain theoretical guidance for further exploring the structure-activity relationship. Meanwhile, AMAP-1 and AMAP-2, especially AMAP-2, from Atractylodis Macrocephalae Rhizoma show potential as immune adjuvants.