[Synthesis, characterization, and immunological activity of Rehmannia glutinosa seleno-polysaccharides]

The present study explored the optimum synthesis process of Rehmannia glutinosa seleno-polysaccharides with acetic acid as a catalyst, characterized the structure of R. glutinosa seleno-polysaccharides by Fourier transform infrared spectroscopy(FT-IR), scanning electron microscopy(SEM), thermogravimetry(TG), and atomic force microscopy(AFM), and preliminarily investigated the immunological activity of R. glutinosa seleno-polysaccharides. The results showed that the optimal conditions for the synthesis of R. glutinosa seleno-polysaccharides included m(acetic acid)∶m(R. glutinosa polysaccharides)=0.80, m(Na_2SeO_3)∶m(R. glutinosa polysaccharides)=1.25, reaction temperature of 80.0 ℃, and reaction time of 7.0 h. Under these conditions, the selenium content of R. glutinosa seleno-polysaccharides was 2.239 mg·g~(-1). The acetic acid catalysis method was milder than the nitric acid method, without affecting the structure of polysaccharides. The results of IR, SEM, TG, and AFM showed that R. glutinosa seleno-polysaccharides were properly prepared. The results of immunological activity showed that compared with the control group, R. glutinosa seleno-polysaccharides could significantly promote the phagocytic capacity of mouse monocyte macrophages and improve the spleen index and thymus index of mice. In the concentration range of 15-240 μg·mL~(-1), the proliferation of spleen lymphocytes of mice was strengthened, and the IL-2 and IFN-γ secretion by Th1 cytokines was promoted. This study can provide references for the further development and application of R. glutinosa polysaccharides.