A new colorimetric method for CUPRAC assay with using of TLC plate

Cupric reducing antioxidant capacity (CUPRAC) method is one of the most widely used antioxidant methods. However, its need for a spectrophotometer, as in many other methods, is an important disadvantage. Cupric reducing antioxidant capacity was determined based on color analysis with Image J program in computer with the new method developed in this study and thus, use of spectrophotometer was eliminated. The new colorimetric CUPRAC assay was applied to various standard antioxidants and plant extracts. The reaction mixtures were dropped on TLC plate. The colors formed on TLC were transferred to the computer by using scanner images, and CTEAC value in μmol/L of each sample was determined with the image J program. The CTEAC values were compared with the TEAC values measured with the spectrometric method. A linear relationship was found between both (C)TEAC values of antioxidant standards (R2 = 0.991) and plant extracts (R2 = 0.994). Thus, the new method developed for the CUPRAC antioxidant assay can be easily performed in any environment without spectrophotometer device, and it is a low-cost method.