Amaranth dye in the evaluation of bleaching of cerium (IV) by antioxidants: application in food and medicinal plants.

A simple, low-cost, sensitive, and diversely applicable spectrophotometric method for the determination of total antioxidant capacity of several medicinal plants and food has been developed. The method is based on the bleaching of cerium (IV) by antioxidants and dye in slightly acid medium at room temperature. The unbleached dye, imparting pink color to the solution, is measured at λ(max) 530 nm which is directly proportional to the antioxidant concentration. The method is reproducible, and the trolox equivalent antioxidant capacities (TEAC coefficients) of the tested antioxidant compounds were correlated with those found by reference method such as ABTS. The recommended method was applied for the determination of total antioxidant capacity of medicinal and food samples. The performance of the recommended method was evaluated in terms of Student's t-test and variance ratio F-test, which indicated the significance of proposed method over the reference method.