w20x. This assay provided information on the reactivity of test compounds with a
stable free radical. Because of its odd electron DPPH gives a strong absorption band
at 517 nm in visible spectroscopy (deep violet color). As this electron becomes
paired off in the presence of a free radical scavenger, the absorption vanishes, and
the resulting decolorization is stoichiometric with respect to the number of electrons
taken up. Propolis extracts with and without CAPE showed a dose-dependent DPPH
quenching capacity. Also in this test the propolis extract with CAPE was more
efficient than propolis extract without CAPE (Fig. 2). CAPE at 2.5 mM concentration
decreased the absorption by 100% and showed a higher quenching efficiency than
galangin.