title: Synthesis and identification of products derived from the metabolism of the carcinostatic 1-(2-chloroethyl)-3-(trans-4-methylcyclohexyl)-1-nitrosourea by rat liver microsomes.
abstract: Liver microsomal metabolism of 1-(2-chloroethyl)-3-(trans-4-methylcyclohexyl)-1-nitrosourea in the presence of reduced nicotinamide adenine dinucleotide phosphate and O2 was shown to produce seven metabolites that included the parent urea. A cytochrome P-450-dependent monohydroxylation of the cyclohexyl ring occurred in 3 positions, cis-3, trans-3, and cis-4, and on the methyl group to form a trans-4-hydroxymethyl derivative. In addition, monohydroxylation of the 2-chloroethyl carbon attached to the N-1 urea nitrogen yielded an alpha-hydroxy metabolite. A ring-hydroxylated derivative remained unidentified while the structures of all other such derivatives were established by comparison with compound synthesized, purified by high-pressure liquid chromatography, and characterized by mass spectral and nuclear magnetic resonance analyses. It was tentatively concluded that some parent urea is formed by a cytochrome P-450 dependent reaction because of a requirement for reduced nicotinamide adenine dinucleotide phosphate and inhibition by CO. Microsomes from rats pretreated with phenobarbital showed about a 3-fold increase in hydroxylation rate while phenobarbital-treated mice microsomes were induced 8-fold. However, in both species, the induced hydroxylation rate was about 4 nmol/min/mg protein. When microsomes from phenobarbital-induced rats were used, a mixture of 80% CO:20% O2 decreased the rate of formation of all metabolites to 14% of that in 80% N2:20% O2.
mesh_terms: D000818:Animals; D002248:Carbon Monoxide / Q000494:pharmacology; D055598:Chemical Phenomena; D002621:Chemistry; D006900:Hydroxylation; D066298:In Vitro Techniques; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D013058:Mass Spectrometry; D051379:Mice; D008862:Microsomes, Liver / Q000378:metabolism*; D009607:Nitrosourea Compounds / Q000378:metabolism*; D010634:Phenobarbital / Q000494:pharmacology; D051381:Rats; D012673:Semustine / Q000031:analogs & derivatives / Q000138:chemical synthesis / Q000378:metabolism*
chemical_list: D009607:Nitrosourea Compounds; D012673:Semustine; D002248:Carbon Monoxide; D010634:Phenobarbital