What is the ORAC Assay?
The Oxygen Radical Absorption Capacity (ORAC) assay is a method for measuring the total serum antioxidant activity. It can quantitatively measure the total antioxidant capacity as well as qualitatively measure the amount of fast Vs slow acting antioxidants in a blood serum sample. The assay utilizes the free radical sensitive flourescent indicator protein -phycoerythrin (beta-PE) to monitor the effectiveness of various serum antioxidants in protecting the beta-PE from becoming damaged by free radicals.

Assay results are quantitated by allowing the reaction to reach completion and then integrating the area under the kinetic curve relative to a blank reaction containing no added antioxidants. The area under the curve is proportional to the concentration of all the antioxidants present in the sample. Example of a typical whole serum ORAC assay curve.

Each reaction is calibrated using known standards of Trolox®, a water soluble vitamin E analog. The results of the assay are reported on the basis of 1 ORAC unit = 1 micro-M Trolox®.

Example of a ORAC Standards, Standard Curve.