Volatile Antioxidants Formed from an L-Cysteine/D-Glucose Maillard Model System

The microwave-induced volatile compounds formed from an l-cysteine/d-glucose Maillard model system at different pHs were evaluated for antioxidative activity using a newly developed method. The dichloromethane extracts of pH 9 and 5 showed the strongest antioxidative effects. Fractionation of the pH 9 extract by column chromatography revealed three fractions possessing antioxidative activity. 2,4,5-Trimethyloxazole, 2,4,5-trimethylthiazole, 4,5-dimethylthiazole, oxazole, thiazole, and 2,5-dimethyl-4-hydroxy-3(2H)-furanone (DMHF) were identified in these fractions as volatile antioxidants. The strongest antioxidative activity was displayed by DMHF, followed by the oxazoles, whereas the thiazoles showed only slight activity. Trimethylpyrazine, another major volatile compound produced in the Maillard reaction, did not show any antioxidative activity. The antioxidative activities of these heterocyclic volatiles were directly dependent upon their concentrations.