Antioxidant, ROS, and free radicals can be measured with the ORAC assay
These ROS molecules are involved in signaling cascades that help the body to respond to these external stimuli. However, too many ROS molecules can have an adverse effect on the body, which can are caused by these molecules interacting with DNA, proteins, or lipids. Cancer, aging, neurodegeneration, cardiovascular and other diseases have been shown to be influence by ROS or free radicals. As a consequence, the body has different ways to eliminate these ROS molecules, which include enzymes (catalase, glutathione peroxidase, etc.) that break down the molecules and biological antioxidants ((transferrin, ceruloplasmin, urate, etc.) that make the molecules inert. Another way to help the body eliminate free radicals is through diet, that is eating antioxidant laden foods such as blueberries or pecans.
To help aid in the research of antioxidants, a method was designed that can measure the antioxidant capacity of a particular substance. This method, the Oxygen Radical Antioxidant Capacity assay or ORAC, is now used routinely to estimate the antioxidant capacity of a particular substance. This method was first adapted to a microplate format by Dr. Ron Prior at the University of Arkansas using a FLUOstar microplate reader from BMG LABTECH (Ou, B.; Hampsch-Woodill, M.; Prior, R. L. Development and validation of an improved oxygen radical absorbance capacity assay using fluorescein as the fluorescent probe. J. Agric. Food Chem. 2001, 49, 4619-4926). Since then the ORAC assay has become one of, if not the most common method to measure antioxidants.
Find out more about the ORAC assay, free radicals, and ROS molecules here: http://www.bmglabtech.com/orac/.