Metabolism of stanozolol: Identification and synthesis of urinary metabolites

Abstract

Urinary metabolites of stanozolol (17α-methyl- 17β -hydroxy-5α-androst-2-eno(3,2-c)-pyrazole) following oral administration were isolated by chromatography on XAD-2 and by preparative high-performance liquid chromatography (HPLC) and identified by gas chromatography-mass spectrometry (GC/MS) with electron impact (EI)-ionisation. Stanozolol is excreted as a conjugate but is metabolized to a large extent. All identified metabolites are hydroxylated, namely at C-3' of the pyrazole ring and at C-4β, C-16α and C-16β of the steroid. Less than 5% of the metabolites are found in the unconjugated urine fraction: 3'-hydroxystanozolol ( II) and 3'-hydroxy-17-epistanozolol ( III). Conjugated excreted metabolites are 3'-hydroxystanozolol ( II), stanozolol ( I), 4β-hydroxystanozolol ( IV), 16β-hydroxystanozolol ( V), 16α-hydroxystanozolol ( VI), two isomers of 3',16-dihydroxystanozolol ( VII, VIII), two isomers of4β,16-dihydroxystanozolol ( IX, X) and a 3',?-dihydroxystanozolol ( XI). 3'-Hydroxystanozolol, 4α-hydroxystanozolol, 4β-hydroxystanozolol, 16α-hydroxy-, 16α-hydroxy-17-epi- and 16β-hydroxystanozolol were synthesised to confirm the structural assignment of the main metabolites.