Antioxidant capacity is an overall ability of organisms or food to catch free radicals and prevent their harmful effect. Antioxidative effect includes protection of cells and cellular structures against harmful effect of free radicals, especially oxygen and nitrogen. Substances with antioxidative properties are called antioxidants.
Antioxidative systems include antioxidative enzymes, that is, superoxide dismutase, catalase, glutathione peroxidase, glutathione-S-transferase, and nonenzymatic substrates, such as glutathione, uric acid, lipoic acid, bilirubin, coenzyme Q, vitamin C (L-ascorbic acid), vitamin A (retinol), vitamin E (tocopherol), flavonoids, carotenoids, and others. Some biomolecules are also considered biologically active and clinically significant antioxidants, for example, transferrin, ferritin, lactoferrin, ceruloplasmin, hemopexin, haptoglobin, and uric acid.
G-Biosciences’ DMPD assay kit measures the antioxidant activity of compounds that are able to transfer hydrogen atoms.
When the compound N,N-dimethyl-ρ-phenylenediamine (DMPD) is in the presence of a suitable oxidant solution, a colored radical cation is formed (DMPD•+). Antioxidant compounds, which can transfer a hydrogen atom to DMPD•+, cause a decoloration of the solution.
In our assay a solution of DMPD at an acidic pH and in the presence of a suitable oxidant solution, can form a stable and colored radical cation (DMPD•+) which shows a maximum of absorbance at 553 nm. Antioxidant compounds which can transfer a hydrogen atom to DMPD•+ quench the color and produce a decoloration of the solution which is proportional to their amount. This reaction is rapid and the end point, which is stable, is taken as a measure of the antioxidative efficiency.
DMPD (uncolored) + Oxidant + H+ → DMPD• + (purple)(λmax= 553 nm)
DMPD• + (purple) + AOH → DMPD(uncolored) + AO