The DPPH test provided information about the reactivity of the tested compound with a stable
free radical. Because of its odd electron, the DPPH radical showed a strong absorption band at
5 15 nm in visible spectroscopy (a deep purple color). As this electron is paired off in the
presence of a free radical scavenger, absorption vanishes and the resulting decoloration is
stoichiometric with respect to the number of electrons taken up. This bleaching of DPPH
absorption, which occurs when the odd electron of the radical is paired, is thus representative of
the capacity of the compounds to scavenge free radicals independently of any enzymatic activity.