Abstract: Objective: To prepare a water-soluble polysaccharide and its iron complex from Radix Glehniae and to study their physicochemical properties, structural characteristics and biological activity. Methods: The polysaccharide was obtained by water extraction and alcohol precipitation and it was reacted with ferric chloride upon heating to synthesize polysaccharide-iron complex. The physicochemical properties and structural characteristics of the polysaccharides and its iron complex were determined by UV-Vis spectroscopy, infrared spectroscopy, high performance anion-exchange chromatography, transmission electron microscopy, and differential scanning calorimetry coupled with thermogravimetric analysis. The hydroxyl radical scavenging capacity and the inhibitory activity against α-glucosidase were also investigated. Results: The polysaccharide yield was 18.4%. The polysaccharide was composed of glucose and mannose with a molar ratio of 1.00:4.25. The polysaccharide-iron complex contained 19.31% iron ions, and it was based on polymerized β-FeOOH micronucleus as the core with surface complexation of polysaccharide. Both the polysaccharide from Radix Glehniae (GLP) and its iron complex (GLP-Fe) had hydroxyl radical scavenging activity and inhibitory effect against α-glucosidase, with the latter being more effective. Conclusion: The hydroxyl radical scavenging effect and α-glucosidase inhibitory effect of the water-soluble polysaccharide from Radix Glehniae were improved after being complexed with iron ions.

Key words: Radix Glehniae, polysaccharide, iron complex, hydroxyl radicals, α-glucosidase inhibitor