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Abstract
Maillard reaction products were prepared by heating xylose and lysine at pH 9.0 and 100°C for 3 h, and then fractionated by ethyl ether and ethanol into acidic, neutral and basic low-molecular-weight, ethanol-soluble and ethanol-insoluble fractions. The ethanol-soluble and -insoluble fractions were the major fractions of the xylose-lysine Maillard reaction products (XL MRPs), contributing 79.5% and 20.1%, respectively. XL MRPs revealed an inhibitory effect on linoleic acid peroxidation induced by the Fenton reaction, but did not inhibit liposome peroxidation induced by Fe2+, where it had a prooxidative action. XL MRPs caused oxidative damage to deoxyribose and 2′-deoxyguanosine (2′-dG) induced by the Fenton reaction. The ethanol-soluble and -insoluble fractions also caused oxidative damages while the low-molecular-weight fractions displayed an antioxidative effect in inhibiting the oxidative damage to deoxyribose that was induced by the Fenton reaction. The prooxidative action of the ethanol-soluble and -insoluble fractions resembled that of the untractionated products in the 2′-dG assay. In these systems with deoxyribose, 2′-dG, linoleic acid and liposomes, XL MRPs exhibited either antioxidative or prooxidative properties, which might have been due to competition between their reducing power and scavenging activity toward the hydroxyl radical. However, the low-molecular-weight fractions did not show any prooxidative activity in these oxidation systems.