Inhibition of ascorbate oxidation by urate

Cupric sulfate is reduced by ascorbate to the cuprous ion. The cuprous ion is then oxidized back to the cupric form by oxygen. A steady state concentration of the cupric ion is thus established to maintain a continuous oxidation of ascorbate in the presence of a trace amount of copper. In the presence of urate there is an instantaneous oxidation of ascorbate by the cupric ion. However, urate complexes with the cuprous ion and thus reduces the steady state concentration of the cupric ion. This decrease in cupric ion concentration interrupts ascorbate oxidation. The interaction of urate and cuprous ion was documented by analysis of uv absorption spectrum and the isolation of urate-Cu⁺ by high-pressure liquid chromatography.