Isolation, Purification, Structural Characterization, and the Antioxidant Activities of Polysaccharides Extracted from Isatidis Radix

Graphical In this study, three water-soluble polysaccharides were isolated from Isatidis Radix , which had never been reported before. IRPS-1 and IRPS-2 possess starch branch chains, while IRPS-3 has a stable triple helix structure. Compared to IRPS-1 and IRPS-2, the structure of IRPS-3 has two additional branches, namely →4)Arap(1→ and Ribf(1→. All three polysaccharides exhibited significant antioxidant activities in vitro, with IRPS-3 demonstrating the best activity among them. This study was focused on the objective of investigating the composition, structure, and physicochemical attributes of Isatidis Radix polysaccharides (IRP). Three distinct polysaccharide fractions, IRPS-1, IRPS-2, and IRPS-3, were separated and purified from the crude polysaccharides of Isatidis Radix utilizing DEAE-52 cellulose and Sephadex G-100 columns. A series of technical methods were used to analyze the structure of the three polysaccharides. The analysis indicated that these compounds were heteropolysaccharides, with average molecular weights of 1.17 × 10 5 Da, 1.21 × 10 5 Da, and 1.06 × 10 5 Da. The primary compositional of IRPS-1 and IRPS-2 were glucose and galactose, while IRPS-3 consisted primarily of galactose, glucose, and arabinose. The methylation analysis elucidated that IRPS-1, IRPS-2, and IRPS-3 possessed similar linear backbones but differed in their branches. Distinguished from the other two polysaccharides, IRPS-3 has two additional branches, namely →4)Arap(1→ and Ribf(1→. I 2 -KI experiment showed that IRPS-1 and IRPS-2 had starch branch chains. In addition, IRPS-3 exhibited a stable triple-helix configuration in aqueous milieu and possessed longer side chains and more branches. In vitro antioxidant experiments demonstrated that IRP exhibited good concentration-dependent antioxidant activity. Based on these findings, IRP can be regarded as a potential natural antioxidant.