Assessment of the antioxidative and prooxidative activities of two aminoreductones formed during the Maillard reaction:: Effects on the oxidation of β-carotene, Nα-acetylhistidine, and cis-alkenes

In short-time-heated mixtures of lactose and N-alpha-acetyllysine 1-[N-epsilon-(N-alpha-acetyllysinyl)]-1,2-dehydro-1,4-dideoxy-3-hexulose (C-6-AR) is formed as main product, whereas 3-hydroxy-4-(alkylamino)-3-buten-2-one (C-4-AR) can be obtained in high yields from the Maillard reaction of glucose. Because both compounds have aminoreductone structure, their antioxidative (AOA) and prooxidative activities (POA) were determined and compared to those of ascorbic acid (AA). Concentration-dependent AOA was determined by measuring oxidative degradation of carotene induced by a radical starter. POA in the presence of metal ions was tested in three different systems: oxidation of carotene in emulsion, of N-alpha-acetylhistidine in aqueous solution, and of cis-alkenes in organic solvent. C-4-AR possesses in all model systems AOA and POA, respectively, which are very similar to those of AA. C-6-AR acts also as antioxidant and prooxidant, but its activity is weaker compared to those of C-4-AR and AA. In the carotene assay the substances displayed POA in the presence of several metal ions, such as Cu2+, Mn2+ and Fe3+/EDTA, but the activity with the latter is considerably lower.