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2.4-dinitrophenyl mercapturic acid Figure 18.7 Glutathione conjugation (phase II) biotransformation reaction.

Bioactivation may involve a complicated series of reactions in several tissues. For example, 2,6-dinitrotoluene is first oxidized by cytochrome P450 and conjugated with glucuronic acid in the liver. It is then excreted in the bile, where bacteria reduce one or both nitro groups to amines and split off the glucuronide. These are reabsorbed by the intestines and return to the liver. The amine group is then hydroxylated by P450 enzymes. The resulting compound can react with DNA, causing mutations that can lead to liver cancer. Table 18.4 lists some compounds that are bioactivated.

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