A novel acidic polysaccharide from Isatidis Radix: Structural characterization and immunoregulatory effect in...

The immune system is the ultimate defense against diseases and its dysregulated homeostasis greatly threatens human health. Natural polysaccharides have a variety of biological activities and show promising applications in immunomodulation. In this study, we characterized the structure of the polysaccharide IRPS-TE-3 from Isatidis Radix using morphological analysis, molecular weight analysis, monosaccharide composition analysis, methylation analysis and nuclear magnetic resonance spectroscopy. The results showed that the main chain of the polysaccharide was composed of →4)-α-D-GalpA-(1→,→5)-α-L-Araf-(1 → and a small amount of →2,4)-α-D-GalpA-(1 → and so on interconnected, and the branched chain was mainly composed of α-L-Araf-(1→, α-L-Araf-(1 → and →4)-β-D-Galp-(1 → interconnected and then connected at the O-2 position of the sugar residue →2,4)-α-D-GalpA-(1 → constitutes. After feeding the polysaccharide to zebrafish, IRPS-TE-3 had no toxic effects on zebrafish embryos. Based on the chloramphenicol (CAP)-induced immune injury model of zebrafish, it was found that IRPS-TE-3 could increase the number of immune cells, reduce the content of inflammatory factors, lower the level of ROS, reduce apoptosis, and attenuate intestinal barrier damage. These results indicate that IRPS-TE-3 has good immunomodulatory activity, which provides a basis for its in-depth study in immunomodulation and the development of functional products.