CAP-e (cell-based antioxidant protection in erythrocytes), is a novel in vitro bioassay for antioxidant activity developed by Alexander Schauss, Gitte Jensen, and associates at the American Institute for Biosocial and Medical Research (AIBMR), a private contract research organization (CRO) located in Puyallup, Washington, and Holger NIS, a private CRO located in Klamath Falls, Oregon.
The CAP-e assay is performed by first incubating red blood cells (erythrocytes) with a test sample at a range of concentrations. The cells are then combined with dichloro fluorescein diacetate (DCFDA), which is oxidized in the presence of free radicals to form a green fluorescent byproduct (DCF). In the next step of the assay, exogenous hydrogen peroxide is added at a concentration of 167 mM to artificially induce severe oxidative stress. The antioxidant activity of varying concentrations of the test compound is measured based on the degree of inhibition of DCF-fluorescence, which is an indirect and nonspecific measure of reactive oxygen species production. To date, the assay has been used in 2 published studies, both conducted by AIBMR and Holger NIS.