Effects of ascorbic acid on the nonenzymatic binding to DNA and the mutagenicity of N-hydroxylated metabolite of a tryptophan-pyrolysis product

Ascorbic acid enhanced the nonenzymatic binding of the mutagen 3-hydroxyamino-1-methyl-5H-pyrido4,3-b]indole (N-OH-Trp-P-2) to DNA with a concomitant increase in the mutagenicity of N-OH-Trp-P-2. The covalent binding of N-OH-Trp-P-2 to DNA was higher at pH 7.4 than pH 6.2 or 5.0. Ascorbic acid increased the binding of N-OH-Trp-P-2 at all pH levels examined. These results indicate that ascorbic acid enhances the DNA damage caused by N-OH-Trp-P-2.