Preparation, structural analysis and physicochemical properties of the Cordyceps cicadae exopolysaccharide iron complex

Abstract

In this study, EPS-Fe(III) complexes were synthesized, and their structural characteristics, thermal stability, antioxidant activity and digestive properties were evaluated. The content of iron in the EPS-Fe(III) complex was 6.34 ± 1.43 %. The absorbance bands of EPS and EPS-Fe(III) complexes were easily changed, indicating that iron ions can interact with the hydroxyl or carboxyl groups of EPS. Energy spectrometric analysis showed that a strong iron signal was observed in the EPS-Fe(III) complex. The IC₅₀ values of the EPS-Fe(III) complex for DPPH, hydroxyl radical and ABTS were 1.52 mg/mL, 2.63 mg/mL and 1.20 mg/mL, respectively. Under oxidative stress, EPS-Fe(III) can prolong the lifespan of nematodes through the DAF-16 and SKN-1 pathways. Under the condition of gastric juice and intestinal juice, the iron content released from artificial intestinal juice reached 66 %. In addition, the negative effect of trypsin or polyphenols on the solubility of iron in EPS-Fe(III) digestive solution was lower than that in ferric chloride digestive solution. In conclusion, the EPS-Fe(III) complex can be used as a new type of iron supplement, which has good antioxidant activity, high stability and good water solubility.

Keywords: Antioxidant activities; Cordyceps cicadae; Digestion properties; Exopolysaccharides; Iron.