Metabolic Activation of Proestrogens in the Environment by Cytochrome P450 System

Liver microsome-mediated activation of proestrogens in the environment is reviewed here. Proestrogens such as methoxychlor, trans-stilbene, diphenyl, diphenylmethane, 2,2-diphenylpropane, benzo[a]pyrene, benzophenone, 2-nitrofluorene (NF), chalcone, trans-4-phenyl-3-buten-2-one and styrene oligomers are negative in in vitro estrogen screening tests. However, those proestrogens exhibit estrogenic activity after metabolic activation by the microsomal cytochrome P450 system. In these cases, hydroxylated derivatives of the compounds are formed as major metabolites, and these metabolites exhibit significant estrogenic activities. Thus, the estrogenic activities of proestrogenic compounds are a consequence of metabolism of the parent compounds. Various candidates for proestrogens among medicines and insecticides are also discussed.