Electron paramagnetic resonance (EPR) spectroscopy of
spin probes is widely used in model membrane investigations
and also in living systems (Mojović et al., 2005). Using DPPH
(2,2-diphenyl-1-picrylhydrazyl) for evaluation of free radicalscavenging
capacities of natural anti-oxidants was proposed
by Blois more then half century ago. DPPH is a stable free
radical and one of the most widely used substances as a
primary standard in quantitative EPR spectrometry (Yordanov
et al., 1996). Since reactive oxygen species (ROS) can react
with biomolecules to form organic, hydrophilic radicals, we
performed series of experiment to evaluate the ability of olive
leaves preparations to remove such reactive species. The
reduction of DPPH in the presence of an extracts is customary
monitored by measuring the intensity of EPR signals.