A study of the antioxidant properties of Keggin-type polyoxometalates

In this paper, we used extracellular reactive oxygen radical scavenging assay and cellular antioxidant assay to investigate the antioxidant ability of Keggin-type polyoxometalates on the inside and outside of cells influenced by three different factors: heteroatom substitution, transition metal substitution and the number of vanadium substitutions. The results showed that the IC₅₀ values of heteroatomic (P, Si, Ga) polyoxometalates on superoxide anion radical scavenging were 1.32 ± 0.00047 mg mL^-1, 17.49 ± 2.47500 mg mL^-1, and 66.99 ± 20.0227 mg mL^-1, respectively. In comparison, PMo₁₂ had the best ability to scavenge free radicals, and the SOD activity of PMo₁₂ at 12.5 μmol L^-1 increased by 50% compared with that of the unspiked drug, which played an antioxidant role; the scavenging effect of superoxide anion radicals of PMo₁₁Mn in transition metals (Fe, Mn, Cu) instead of polyoxometalate (IC₅₀ value 1.18 ± 0.0008 mg mL^-1) was lower than that of unsubstituted PMo₁₂ (IC₅₀ value 1.32 ± 0.00047 mg mL^-1), where PMo₁₁Mn was nearly 1.5 times higher than PMo₁₁Cu administration to reduce the number of cells by half; the PMo₁₁V, PMo₁₀V₂, PMo₉V₃, PMo₈V₄, PMo₇V₅ hydroxyl radical scavenging rates (IC₅₀ values) were 0.19 ± 0.0011 mg mL^-1, 0.22 ± 0.0027 mg mL^-1, 0.03 ± 0.0014 mg mL^-1, 0.04 ± 0.0008 mg mL^-1, and 0.11 ± 0.0005 mg mL^-1, respectively, and in comparison, scavenging of PMo₉V₃ radicals was more effective and they acted as an antioxidant. Therefore, they can be used as good antioxidants in biological and pharmaceutical applications and play an important role in the treatment of tumours, cancer, Alzheimer's disease and other diseases.