The mode of DNA-breaking actions of ascorbic acid (AsA) and triose reductone (TR) in the presence of Cu2+ was studied by use of 0.8% agarose slab gel electrophoretic analysis. The DNA-breaking actions of the mixture of AsA or TR and Cu2+ were inhibited by N2 gas, hydroxyl radical scavengers and catalase, indicating that the oxidation of AsA or TR by Cu2+ and the hydrogen peroxide and hydroxyl radicals resulting from the oxidation are essential for the fragmentation of DNA by the mixture of AsA or TR and Cu2+. However, the DNA-breaking activity of these reductones varied with pH, while their oxidation rates were proportional to the increase in pH. The marked fragmentation of DNA occurred at pH 4, 7 or 8. The breakages of DNA by AsA or TR in the presence of Cu2+ were concluded not to be associated with the oxidation rates of reductones.
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