Antioxidant defenses of baker's yeast against free radicals and lipid peroxides in rat brain.

We examined through the electron spin resonance spectrometry/spin trapping technique the antioxidant activity of baker's yeast Saccharomyces cerevisiae which is known to have both enzymatic and nonenzymatic antioxidants. The components in baker's yeast were separated by differential filtration/centrifugation using centrifuge-type filter tubes, yielding four nonenzymatic thermostable fractions of varied molecular weights which scavenged 85-95% of 1,1-diphenyl-2-picrylhydrazyl in organic solution, of hydroxyl and superoxide radicals in aqueous solution, and of lipid carbon-centered radicals induced by equimolar mixture of ascorbic acid and Fe(II) salt in rat brain homogenate. Baker's yeast also inhibited the thiobarbituric acid-reactive substance formation in the cortex, midbrain, pons-medulla oblongata, cerebellum, hippocampus, and striatum. Partial characterization of the antioxidative defenses in baker's yeast against free radicals and lipid peroxides in the brain confirmed the presence of superoxide dismutase, catalase, peroxidase, and glutathione.