Sijunzi Decoction (SJZD) is a conventional prescription for curing spleen deficiency in Traditional Chinese Medicine and polysaccharide is its main ingredient. In order to explore the effective ingredients contributing to the immunological activity of SJZD, we isolated and purified seven homogeneous polysaccharides from Radix Ginseng (RS-3-1 and RS-3-2), Rhizoma Atractylodis Macrocephalae (BZ-3-1, BZ-3-2, and BZ-3-3), Poria (FL-3-1), and Radix Glycyrrhizae (GC-3-1) decoctions, respectively. The molecular weight of seven homogeneous polysaccharides ranged from 5.42 × 104 to 5.65 × 104 Da. Monosaccharide composition determined by GC-MS analysis showed that these polysaccharides were primarily composed of Rha, Ara, Xyl, Man, Glc, and Gal with various ratios. Immunological activity assay revealed that polysaccharides from four crude drug components of SJZD displayed inhibitory effects on the complement system. RS-3-1, BZ-3-1, FL-3-1, and GC-3-1 could significantly enhance the phagocytosis and increase the NO production and tumor necrosis factor (TNF-α) level in RAW 264.7 cells (p < 0.05). These results demonstrated the immunological activities of these polysaccharides from the four crude drugs. This study supports the therapeutic effect of SJZD in clinical use and is essential for further identification the immunopolysaccharide from SJZD decoction.

Sijunzi decoction (SJZD) is a classical herbal prescription in traditional Chinese medicine (TCM) used for enhancing the function of immune system. In previous studies, a polysaccharide fraction S-3 was screened from SJZD by assessment of immune system regulation, intestinal microbiota, and SCFA in order to explore the immune active ingredients in SJZD. In the present study, S-3 was further purified, and a homogeneous polysaccharide S-3-1 with a molecular mass of 13.5 × 10 4 Da was obtained after further fractionation by Sephadex G-150 size-exclusion chromatography. The immunological activities of S-3-1 were assayed in vitro for the first time. The determination of the anticomplement activity showed that S-3-1 displayed inhibitory effects on classical pathway of the complement system, with CH 50 values of 530 g/mL. The FT-IR analysis showed that S-3-1 had absorptive peaks characteristic of polysaccharides. The methylation and GC-MS analysis showed that it is comprised of Rha, Ara, Xyl, Man, Gal, and Glc in a relative molar ratio of 0.35 : 0.37 : 1.4 : 0.31 : 3 : 0.8 and that it mainly contained 1,4-linked-Glc and 1,6-linked-Gal glycosidic bonds. The morphology of S-3-1 was observed by atomic force microscope (AFM). These results provided evidences for tracking the material basis of SJZD immune activity.