Determination of the activity of an antioxidant by the DPPH° assay

Analyzing the results

For each antioxidant concentration, plot the curve representing the evolution of the residual DPPH° with time and extract the plateau value.
Plot these values on a graph as a function of antioxidant concentration. This is the “dose-response curve”.
Determine the value of the “effective concentration” EC₅₀, which is the antioxidant concentration required to reduce 50% of the initial DPPH°. Depending on the type of antioxidant tested, EC₅₀ is expressed in mol/L (pure antioxidant) or in g/L (plant extracts).

Decreasing curve with the antioxidant concentration on the x-axis and the residual DDPH° on the y-axis at the plateau in %. The point at 50% residual DDPH° is at the concentration noted EC50. The lower the EC50, the more effective the antioxidant.

DDPH° kinetics of a green tea extract. 5 curves with the same origin but a more and more rapid decline represent 0.5, 1, 1.5, 2 and 3 mg/L.