Inhibition of ascorbate autoxidation by a rat brain cortical factor

The soluble fraction of rat brain cortex yielded an antioxidant factor that inhibits the autoxidation of ascorbic acid at physiological pH. The measurements were based on spectrophotometric detection of ascorbic acid at 265 nm in a physiological salt solution of the Krebs-Ringer type, pH 7.4, or in sodium phosphate buffer, pH 7.4. In these systems the autoxidation of ascorbate was linear with respect to time for at least 60 min. The potency of the antioxidant factor is indicated by the fact that half maximal inhibitory activity was obtained with an extract representing approximately 10,000-fold dilution of cell components. The inhibitory activity of the cortical tissue was solubilized during heat treatment. A considerable portion of the activity was released by brain slices into the medium during incubation in normal Krebs-Ringer phosphate medium.