The optimal conditions for preparing Zn-Flammulina velutipes polysaccharide (Zn-FVP) chelate were studied by using L 9 (3 4) orthogonal test. The results showed that the optimized conditions for the chelating reaction were as follows: initial concentration of Zn (II), 6 mg/mL; ratio of purified polysaccharide (FVPp) to Zn (II), 1:2; chelating time, 8 h; and pH, 5. Chelating rate achieved 98.11% under the optimal conditions. Characteristic bands for OH stretching at 3000-3500 cm −1 and bands corresponding to C-H variable angle vibration between 1000-1100 cm −1 showed some obvious differences for chelation of polysaccharides and zinc. The qualitative spectrum of Zn-FVP indicated the presence of ZnSO 4 and the abundant Zn (II) groups were widely present in the chelated samples. The anti-inflammatory effect of FVPp and Zn-FVP on Lipopolysaccharide-stimulated RAW 264.7 cells was evaluated. In the range of 5-50 μg/mL, Zn-FVP did not exhibit obvious inhibition of the survival rate of cells. Zn-FVP in noncytotoxic levels showed strong suppressive effect on the inflammatory cytokines (IL-6, TNF-α, INF-γ and NO) and these provided a theoretical base for the anti-inflammatory mechanism of Zn-FVP.

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