Effect of Reaction Time on DPPH and ABTS+ Radical Scavenging Assays for Antioxidant Capacity Evaluation

Due to the operation simplicity of DPPH and ABTS+ radical scavenging arrays for evaluating antioxidant capacity and without a need for specific equipments, both assays have been widely chosen to evaluate antioxidant capacity. EC50 is generally used as a representative parameter for antioxidant capacity of antioxidants determined using DPPH· assay at 30 min of fixed reaction time or using ABTS+· assay at 6 min of fixed reaction time. The results of this investigation indicated that a big difference was made by the compositions and structures of antioxidants to reaction rates with DPPH·and ABTS+·free radicals. The reaction equilibrium time was also different so that wrong estimations might be achieved at the condition of fixed reaction time.