Antioxidant Properties of Heterocyclic Intermediates of the Maillard Reaction and Structurally Related Compounds.

It is well established that a wide range of reductones is formed in the course of the Maillard reaction and that these substances contribute to the oxidative stability of food. The aim of this study was to analyze 12 important heterocyclic intermediates with and without reductone structure as well as structurally related substances under equal conditions to compare their antioxidant properties in detail. For this purpose, five methods were selected including photometrical methods such as the trolox equivalent antioxidant capacity assay and an electron paramagnetic resonance spectroscopic method. Reductones with furan-3-one structure and 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one were reducing in all assays, whereas isomaltol and maltol did not react in assays based on the reduction of metal ions because of their complexing abilities. The introduction of protecting groups to the free hydroxyl functions of selected reductones could nearly eliminate their reducing abilities. In addition, the oxidation products of the different reductive heterocycles were compared after treatment with iodine. Mainly short-chained organic acids such as lactic, glycolic, and glyceric acid are formed as result of the degradation, which indicates 1,3-dicarbonyl cleavage reactions of corresponding tricarbonyl compounds as intermediates of the oxidation.