Studies on anabolic steroids: V. Sequential reduction of methandienone and structurally related steroid A-ring substituents in humans: gas chromatographic—mass spectrometric study of the corresponding urinary metabolites

Abstract

The biotransformation of methandienone (17β-hydroxy-17α-methylandrosta-1,4-dien-3-one) in human adults, more particularly the sequential reduction of its A-ring substituents, was investigated by gas chromatography—mass spectrometry. Two pairs of 17-epimeric tetrahydro diols resulting from the stereoselective reduction of the Δ 4- and 3-oxo groups and of the Δ 1-function were characterized. The major diols were 17α-methyl-5α-androstane-3α,17β-diol and 17α-methyl-5β-androstane-3α,17β-diol, which were both excreted in the conjugate fraction in a 1:3.8 ratio. The immediate metabolic precursors of the 5β-diol, namely 17β-hydroxy-17α-methyl-5β-androsta-1-en-3-one and 17α-methyl-5β-androsta-1-en-3α,17β-diol and their corresponding 17-epimers, were also identified in post-administration urine samples. These data indicated that reduction of methandienone A-ring substituents proceeds according to the sequence. Δ 4-, 3-oxo- and Δ 1-. The A-ring reduction products of the structurally related steroids mestanolone, 17α-methyltestosterone and oxymethone were also characterized and provided further analytical and metabolic evidence supporting the proposed route of methandienone A-ring reduction. It was also demonstrated using synthetic 17β-sulfate conjugates of methandienone and 17α-methyltestosterone that their corresponding 17-epimers are formed by nucleophilic substitution by water of the labile sulfate moiety. The steroidal metabolites were identified on the basis of their characteristic mass spectral features and by comparison with authentic reference standards. Metabolic pathways accounting for the occurrence of the metabolites of interest in post-administration urine samples are proposed.