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. Antioxidants are substances with antioxidative properties. They are most commonly present in fruits and vegetables. In addittion, other foods such as wine, meat or eggs contain these substances.
DMPD Antioxidant Capacity Assay Kit
Bioquochem recommends DMPD assay kit for antioxidant measurements of beverages. This 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•+). Then, antioxidant compounds, which are able to transfer a hydrogen atom to DMPD•+, cause a decoloration of the solution.
In our assay a solution of DMPD at an acidic pH, 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. Then, antioxidant compounds which are able to 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, corresnponds to a measure of the antioxidative efficiency.
DMPD (uncolored) + Oxidant + H+→ DMPD•+(purple)(λmáx= 553 nm)
DMPD•+(purple)+ AOH → DMPD(uncolored) +AO
Scheme 1. Formation of radical DMPD and its reaction with antioxidants (AOH)