Background
The search for new natural or synthetic products with antioxidant activity is commonly based on
Conclusion
The DPPH and ABTS reduction methods were optimized and validated on a microscale and could be expected to be implemented in any laboratory.
Methods
Optimization was carried out using both a fractionated factorial design and a basic sequential simplex method, by monitoring the reduction percentage. Quercetin or Trolox were used as positive con-trol. Furthermore, for each method, linearity, precision, accuracy, robustness, plate uniformity, signal variability, and Z factor, were established.
Results
The optimized conditions for the DPPH method were: DPPH 280 μM in ethanol and 15 min of reaction time in the dark. The linear range was between 7 and 140 μM with an R2 value of 0.9987. The optimized conditions for the ABTS method were: ABTS adjusted to 0.7 absorbance units, 70% concen-tration in ethanol, and a reaction time of 6 min in the dark. The linear range was found to be between 1 and 70% with an R2 = 0.9991. For both methods, the accuracy and precision were within limits and the Z factor value was higher than 0.89. The applicability of each method was assessed by analyzing eight plant extracts.