Volatile products prepared from a browning model system consisting of D-glucose/L-cysteine and related heterocyclic compounds were evaluated for antioxidative activity, measured by the oxidation of hexanal to hexanoic acid either in the dark or in sunlight. In the case of the experiments in the dark, the volatile browning reaction mixture inhibited hexanoic acid formation by almost 100% for up to 13 days. Some column chromatographic (CC) fractions of the above reaction mixture exhibited activities comparable to that of whole samples. Imidazole, 2-thioimidazole, and 2-methyl-3-furanthiol exhibited some inhibitory activity. In the case of the experiments in sunlight, the reaction mixture and some CC fractions exhibited satisfactory inhibition, whereas some CC fractions showed prooxidative activity. Mixtures of some heterocyclic compounds behaved either as an antioxidant or as a prooxidant after 75 days.