The K-region 5,6-epoxide and non-K-region 1,2- and 3,4-epoxides of
chrysene were isolated by normal phase high performance liquid chromatography (HPLC) from a mixture of products formed in the metabolism of
chrysene by liver microsomes from untreated (control),
phenobarbital-treated, or 3-methylcholanthrene-treated rats in the presence of an
epoxide hydrolase inhibitor, 3,3,3-trichloropropylene 1,2-oxide.
Epoxides were characterized by ultraviolet, mass, and circular dichroism spectral and chiral stationary phase HPLC analyses. Each of the metabolically formed
epoxides was hydrated by rat liver
microsomal epoxide hydrolase to a trans-
dihydrodiol. The metabolically formed
chrysene 5,6-epoxides were determined by chiral stationary phase HPLC and were found to contain (5S,6R):(5R,6S) enantiomer ratios of 68:32 (control), 71:29 (
phenobarbital), and 5:95 (3-methylcholanthrene), respectively. The enantiomers of
chrysene 1,2-epoxide and 3,4-epoxide were also resolved by chiral stationary phase HPLC. However, the enantiomeric compositions of the metabolically formed
chrysene 1,2- and 3,4-epoxides, which racemized rapidly at room temperature, could not be directly determined. By using molecular
oxygen-18 in the in vitro incubation of
chrysene and by mass spectral analyses of the resulting oxygen-18-containing
dihydrodiol metabolites and their
acid-catalyzed
dehydration (phenolic) products, both 1,2-epoxide and 3,4-epoxide were found to be converted by
microsomal epoxide hydrolase-catalyzed water attack at predominantly (greater than or equal to 97%) the allylic carbons.