CUPRAC (CUPric Reducing Antioxidant Capacity) is a mostly new method which, for example, enables TAC measures even in oils.

The main reagent, the copper (II)-neocuproin (2,9-dimethyl-1,10-phenanthroline), can oxidize antioxidants generating a coloured product measurable by colorimetric methods. The chelation with neocuproin enables a fastened reaction by elevating the redox potential of the reagent.

Recent correlations have been saw within many illnesses and ROS (reactive species of oxygen, as superoxide); antioxidants on the other hand have been proved to inhibit this ROS. So the measure of these antioxidants seems an interesting new approach to study not only illnesses, also many other physiological states.
 
Assay Principle
CUPRAC reagent implies an oxidation of an antioxidant with a leading tiol group, like for example gluthation (GSH). In this process, the reagent reduces itself forming a chelate complex of cupper (I) – neocuproin, wich provides color measurable at 450nm in a spectrophotometer. This reaction takes place on physiological pH (or neutral pH, near pH 7).