Abstract
High molecular weight Maillard reaction products (melanoidins) are described to possess metal-chelating properties. Whereas in food systems, this ability contributes to antioxidant properties, the consequences on biological systems are not quite clear. The study was aimed to evaluate the implication of metal complexation by melanoidins on DNA damage. Melanoidins prepared with d-glucose and different l-amino acids under water-free reaction conditions were charged with cupric ions. The effect on isolated DNA was investigated by the PM2 assay and on cellular systems in the human colon carcinoma cell line HCT-116 by alkaline unwinding. Independent of the amino acid composition, pure melanoidins (MW >14 kDa) did not cause significant DNA damage. By charging melanoidins with Cu2+ ions, a considerable DNA strand breaking activity was detectable, which was again amplified in an oxidative milieu (addition of hydrogen peroxide). Since Cu2+ normally does not provoke the formation of reactive oxygen species (ROS) via Fenton-type reaction, the results obtained have to be attributed to reducing properties of melanoidins. Thus, in melanoidin–copper complexes redox cycling may take place leading to Cu+ which subsequently undergoes Fenton-type and Haber–Weiss reactions. As a consequence, ROS are formed, which may explain the generation of DNA strand breaks.
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