In vitro antioxidant activity of Kyoho grape extracts in DPPH• and ABTS• assays: Estimation methods for EC50 using advanced statistical programs

The antioxidant capacities of Kyoho skin, seed, and flesh extracts were determined using DPPH center dot and ABTS(center dot) assays and a suitable statistical program was tested for the prediction of EC50 values of Kyoho skin, seed, and flesh extracts obtained by DPPH center dot and ABTS(center dot) assays. Statistical programs: OriginPro (R) version 8, GraphPad Prism (R) version 7, GraphPad Prism (R) version 7 five-parameter (5P) logistic model, SigmaPlot (R) version 14.0, Microsoft Excel (R) version 2016, interpolation log, and direct interpolation methods were employed to estimate the EC50 values. Linear regression and direct interpolation results showed deviations for non-linear models in the prediction of EC50 values of grape extracts. The correlation results of grape flesh extracts demonstrated a positive correlation (r = >= 0.95) between EC50 values of antioxidant assays. Therefore, non-linear methods were appropriate for EC50 calculations. These findings have significant implications for selecting an efficient statistical tool to calculate EC50 values for DPPH center dot and ABTS(center dot) assays.