Characterization, optimization of preparation process of an Inonotus obliquus polysaccharide-Zinc (II) complex and its antioxidant activities

Zinc deficiency in human body has gradually become a major challenge to public health in modern society. In our previous work, a novel polysaccharide from Inonotus obliquus IP3a was successfully isolated and purified. The preparation process of IP3a-Zn was optimized by response surface methodology based on single factor experiments. Characterization and antioxidant activities of IP3a-Zn were investigated. The optimal preparation process of IP3a-Zn was obtained as follows: chelation time was 6.3 h, zinc (II) initial concentration was 4.6 mg/mL and mass ratio of IP3a to zinc sulfate heptahydrate was 4.8:1(mg/mg). The weight loss of IP3a-Zn was slightly smaller than that of IP3a within the heating temperature range. After chelation with zinc, IP3a-Zn had crystalline properties like IP3a. IP3a-Zn had stronger antioxidant activity than IP3a. The results indicated that chelation with zinc enhanced the antioxidant activity of IP3a. IP3a-Zn may serve as a good source of zinc as a supplement and could be used as an antioxidant for the food industries.