Studies on anabolic steroids—6. Identification of urinary metabolites of stenbolone acetate (17β-acetoxy-2-methyl-5α-androst-1-en-3-one) in human by gas chromatography/mass spectrometry

Abstract

The metabolism of stenbolone acetate (17β-acetoxy-2-methyl-5α-androst-1-en-3-one), a synthetic anabolic steroid, has been investigated in man. Nine metabolites were detected in urine either as glucuronic or sulfuric acid aglycones after oral administration of a single 50 mg dose to a male volunteer. Stenbolone, the parent compound, was detected for more than 120h after administration and its cumulative excretion accounted for 6.6% of the ingested dose. Most of the stenbolone acetate metabolites were isolated from the glucuronic acid fraction, namely: stenbolone,3α-hydroxy-2-methy-5α-androst-1-en-17-one, 3α-hydroxy-2ξ-methyl-5α-androstan-17-one; 3 isomers of 3ξ,16ξ-dihydroxy-2-methyl-5α-androst-1-en-17-one; 16α and 16β-hydroxy-2-methyl-5α-androst-1-ene-3,17-dione; and 16ξ,17β-dihydroxy-2-methyl-5α-androst-1-en-3-one. Only isomeric metabolites bearing a 16α or a 16β-hydroxyl group were detected in the sulfate fraction. Interestingly, no metabolite was detected in the unconjugated steroid fraction. The steroids identities were assigned on the basis of their TMS ether, TMS enol-TMS ether, MO-TMS and d 9-TMS ether derivatives and by comparison with reference and structurally related steroids. Data indicated that stenbolone acetate was metabolized into several compounds resulting from oxidation of the 17β-hydroxyl group and/or reduction of A-ring δ-1 and/or 3-keto functions with or without hydroxylation at the C 16 position. Finally, comparison of stenbolone acetate urinary metabolites with that of methenolone acetate shows similar biotransformation pathways for both δ-1-3-keto anabolic steroids. This indicates that the position of the methyl group at the C 1 or C 2 position in these steroids has little effect on their major biotransformation routes in human, to the exception that stenbolone cannot give rise to metabolites bearing a 2-methylene group since its 2-methyl group cannot isomerize into a 2-methylene function through enolization of the 3-keto group as previously observed for methenolone.