Abstract: Objective: To prepare polysaccharide-iron complex from the bulbs of Fritillaria ussuriensis, and to evaluate its physicochemical properties, structural characteristics and antioxidant activity. Methods: The structure of the polysaccharide extracted by water extraction and then alcohol precipitation was chemically modified to obtain its iron complex. Ultraviolet-visible spectroscopy, infrared spectroscopy, X-ray powder diffraction, scanning electron microscopy (SEM), and thermogravimetric-differential thermal analysis were used to determine the physicochemical properties, and structural characteristics of the polysaccharide and its iron complex. Moreover, their antioxidant activities were evaluated by 1,1-dipheny1-2-picryl-hydrazyl (DPPH), superoxide anion and hydroxyl radical scavenging assays. Results: The extraction yield of F. ussuriensis polysaccharide was 4.66%. The characterization confirmed the successful synthesis of polysaccharide-iron complex. The basic structure framework of the polysaccharide was not changed after complexation with Fe3+. In addition, the structural stability of polysaccharide-iron complex was stronger. The complex had stronger radical scavenging effects than the polysaccharide and the maximum scavenging rates were 68.96%, 57.28% and 46.88% for DPPH, superoxide anion and hydroxyl radicals, respectively. Conclusion: The structural stability of F. ussuriensis polysaccharide increased after being modified with Fe3+, leading to a significant increase in the antioxidant activity in vitro.

Key words: Fritillaria ussuriensis, polysaccharide, iron complex, antioxidant activity, chemical structure