The alcoholic extract of Acanthus ilicifolius leaves inhibited the formation of oxygen derived free radicals (ODFR) in vitro with IC(50) of 550 microg/ml, 2750 microg/ml, 670 microg/ml and 600 microg/ml (Fe(2+)/ascorbate system), 980 microg/ml (Fe(3+)/ADP/ascorbate system) for superoxide radical