Effects of different steaming times on the composition, structure and immune activity of Polygonatum Polysaccharide

As a commonly used traditional Chinese herbal medicine, Polygonati Rhizoma has high medicinal value, it can enhance the immune capacity of the body, regulate the metabolism of blood glucose and lipids, treat weakness of the stomach and intestines and physical fatigue, and so on. There are three plant varieties of Polygonati Rhizoma recorded in Chinese Pharmacopoeia, including Polygonatum sibiricum Red., Polygonatum kingianum Coll. et Hemsl. and Polygonatum cyrtonema Hua, compared with the first two, Polygonatum cyrtonema Hua is less studied. Polygonatum cyrtonema Hua is one of the basal plants of the Chinese herb Polygonati Rhizoma, that strengthens the spleen, moistens the lungs, and benefits the kidneys. Polygonatum polysaccharide is the main active substance of Polygonatum cyrtonema Hua, which has various biological effects of regulating immune system, anti-inflammatory, anti-antidepressant, antioxidant and other effects.

In order to analyze the necessity and scientificity of multiple cycles of steaming during the traditional nine-steaming and nine-drying process of the concoction of Polygonatum, we investigated the changes in the composition and structure of polysaccharides, and explored its immunomodulatory activity and molecular biological mechanism.

The structural characterization and molecular weight of polysaccharides were studied by scanning electron microscope (SEM), high-performance size exclusion chromatography-evaporative light scattering detector (HPSEC-ELSD) and Matrix.assisted laser resolutionu ionization time-of-flight mass spectrometry (MALDI-TOF-MS). The composition and proportion of monosaccharides were determined by PMP-HPLC method. A mouse immunosuppression model was established by intraperitoneal injection of cyclophosphamide to compare the immunomodulatory effects and mechanisms of different steaming times of Polygonatum, The changes of body mass and immune organ indices of mice were measured; the secretion levels of interleukin-2 (IL-2), interferon γ (IFN-γ) and the expression levels of immunoglobulin M (IgM) and immunoglobulin A (IgA) in serum were determined by enzyme-linked immunosorbent assay; and then flow cytometry was used to detect T-lymphocyte subpopulations to evaluate the differences of immunomodulatory effects of polysaccharides during the processing and preparation of Polygonatum. Finally, the Illumina MiSeq high-throughput sequencing platform was used to analyze short-chain fatty acids and to investigate the effects of different steaming times of Polygonatum polysaccharides on immune function and intestinal flora in immunosuppressed mice.

The structure of the Polygonatum polysaccharide with different steaming times changed significantly, the relative molecular weight of Polygonatum polysaccharide decreased significantly, and the monosaccharide composition of Polygonatum cyrtonema Hua with different steaming times was the same but the content was different. The immunomodulatory activity of the Polygonatum polysaccharide was enhanced after concoction, which significantly increased the spleen index and thymus index, and increased the expression of IL-2, IFN-γ, IgA and IgM. The CD4+/CD8+ ratio of Polygonatum polysaccharide also increased gradually with different steaming times, indicating enhanced immune function and significant immunomodulatory effect. The content of short-chain fatty acids in the feces of mice in both six steaming six sun-drying of Polygonatum polysaccharides (SYWPP) and nine steaming nine sun-drying of Polygonatum polysaccharides (NYWPP) groups increased significantly, including the content of propionic acid, isobutyric acid, valeric acid, and isovaleric acid, and also had a good effect on the regulation and improvement of microbial community abundance and diversity, SYWPP and NYWPP increased the relative abundance of Bacteroides and the ratio of Bacteroides and Firmicutes (B:F), while SYWPP significantly increased the abundance of Bacteroides, Alistipes and norank_f__Lachnospiraceae, but the effect of raw Polygonatum polysaccharides (RPP) and NYWPP was not significant than SYWPP.

Overall, both SYWPP and NYWPP could significantly enhance the immune activity of the organism, improve the imbalance of intestinal flora in immunosuppressed mice, and increase the content of intestinal short chain fatty acids (SCFAs), it is noteworthy that SYWPP has a better effect on the improvement of the immune activity of the organism. These findings can explore the stage of the concoction process of Polygonatum cyrtonema Hua to achieve the best effect, provide a reference basis for the development of quality standards, and at the same time promote the application of new therapeutic agents and health foods in raw and different steaming times of Polygonatum polysaccharide.