Structural characteristics and antioxidant activity of polysaccharide-iron complex from Glehniae Radix

The preparation conditions of Glehniae Radix polysaccharide-iron complex (GLP80-Fe) were optimized and the physicochemical properties were characterized by Ultraviolet-visible spectroscopy (UV-Vis), Fourier Transform Infrared Spectroscopy (FT-IR), X-ray diffraction (XRD), Transmission electron microscope (TEM), Thermogravimetric analyzer, and Differential scanning calorimetry (TGA-DSC), respectively. The stability and reducibility of GLP80 and GLP80-Fe were analyzed, and the monosaccharide composition was determined by gas chromatograph (GC). In vitro antioxidant activity of GLP80 and GLP80-Fe were evaluated by determining the radical (DPPH and hydroxyl radical) scavenging abilities. The results showed that the highest iron content of GLP80-Fe (15.61%±0.04) was obtained at the optimum conditions: reaction temperature was 38.0°C, reaction time was 3.0 h, FeCl3 addition was 2.9 mL and pH was 9. GLP80-Fe was a complex with β-FeOOH as the core and polysaccharides on its surface, and it was stable at pH 3 ~ 14. GC showed that the major monosaccharides were mannose (Man) and galactose (Gal) with a ratio of 1:5.15. In vitro free-radical scavenging activity of GLP80-Fe was significantly better than GLP80. The IC50 of GLP80-Fe against DPPH and hydroxyl radical were 3.785 mg/mL and 1.460 mg/mL, respectively.