Gas chromatographic assay of epoxide hydrase activity with 3-methylcholanthrene-11,12-oxide

Epoxide hydrase has been measured in rat tissue with 3-methylcholanthrene-11,12-oxide as substrate; diol formation was assayed by gas chromatographic separation of the trimethylsilylated derivative of trans-11,12-dlhydro-11,- 12-dihydroxy-3-methylcholanthrene from the corresponding derivative of the 11 (or 12)-hydroxy-3-methylcholanthrene on 3 percent OV-17, which is formed from the 11,12-oxide during the derivatization. The polycyclic hydrocarbons were extracted initially from the incubation mixture with ethyl acetate. The assay is simple, inexpensive, and sensitive.