The free radical scavenging effect of "beta catechin", an antioxidant preparation containing green tea extract, ascorbic acid, sunflower seed extract, dunaliella carotene and natural vitamin E, was evaluated. Two techniques were used: electron spin resonance (ESR) spectrometry to measure radical-scavenging activity, and measurement of its effect on iron-induced lipid peroxidation in brain. A 0.05% solution of "beta catechin" completely scavenged 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals (6.1 x 10(15)spins/ml). A 10% solution of "beta catechin" completely scavenged superoxide (4.2 x 10(15) spins/ml) generated by the hypoxanthine-xanthine oxidase system. An undiluted solution of "beta catechin" scavenged about 90% of hydroxyl radicals (3.5 x 10(15) spins/ml) generated by the Fenton reaction. "beta catechin"s effect on the accumulation of thiobarbituric acid-reactive substances (TBARS) was evaluated from tissue obtained from the ipsilateral cortex of FeCl3-induced epileptic rats. Oral administration of "beta catechin" (1 or 2ml/kg body weight) both inhibited TBARS formation and increased the activity of superoxide dismutase (SOD) in the ipsilateral cortex 30 min after iron-salt injection into the left sensory motor cortex. These data suggest that "beta catechin" has an antioxidant effect and may have a prophylactic effect against aging and other neurological diseases related to free radical mechanisms.