Optimization of the Effect of Temperature, Concentration and pH on Antioxidant Capacity by Gallic Acid by Response Surface Methodology (RSM)

The antioxidant capacity of gallic acid (GA) is affected by temperature and pH. Aim: To understand this phenomenon, we evaluated the optimization of conditions between temperature (2°C, -20 °C, 40 °C), pH (3,7,10) and concentrations (1 mM, 4 mM and 7 mM) to have a better antioxidant capacity by response surface methodology (RSM). Methods: The DPPH method was used to measure the percentage inhibition (%Inh). Concentrations, 23 °C and pH 7 were evaluated, respectively. Three temperatures (2°C, -20 °C, 40 °C) were combined with the same concentrations and pH in a Box-Behnken design model. Results: The combination of the three factors significantly influenced the %Inh. The factor levels that resulted in higher %Inh were 2 °C, acidic pH and 4 mM concentration. The RSM showed that the optimum conditions had %Inh values of DPPH of 87.66%, 87.11% and 88.29%, respectively. Conclusion: the antioxidant capacity of GA. at 2 °C and pH 2 creates highest antioxidant capacity of GA.