Biotransformation of 17-alkylsteroids in the equine: gas chromatographic-mass spectral identification of ten intermediate metabolites of methyltestosterone

Detection of stanozolol and its metabolites in equine urine by liquid chromatography?electrospray ionization ion trap mass spectrometry

“…If it is allowed that the hydroxylation site is C16, there are four possible stereochemistries based on variation at C16 and C17. 16␣-Hydroxylation and 17-epimerization have both been reported for stanozolol in humans [1,3], while in the horse they have been variously reported for the analogous anabolic steroids methandrostenolone [15][16][17], 17␣-methyltestosterone [18], fluoxymesterone [19] and norethandrolone [20]. However, given that the accepted method of formation of 17-epimers from 17␣-alkyl-17␤-hydroxysteroids is via spontaneous hydrolysis of the tertiary 17␤-sulfate conjugate in the urine [15], their formation is obviously critically dependant on the phase II metabolism.…”

Identification and quantification of metabolites common to 17α-methyltestosterone and mestanolone in horse urine

“…Studies have shown that structurally related MTS and MSL yield metabolites in common in human [1,2]. There are also reports of the urinary metabolites of MTS in horse; Stanley et al [3] and Dumasia [4] used GC/MS to identify 17-hydroxymethyl metabolites, and McKinney et al examined the stereochemistry of urinary metabolites by comparing with authentic reference standards [5]. The main steps in the metabolism of MTS in horses are as follows: reduction of A-ring 3-oxo and 4-ene groups; oxidation at C-6, C-15, and C-16; and epimerization at C-17 during phase I biotransformation, followed by sulfate and glucuronide conjugation during phase II biotransformation [3,4].…”

Analysis of anabolic steroids in the horse: Development of a generic ELISA for the screening of 17α-alkyl anabolic steroid metabolites

“…HSA (2.5 eq., w/w) was dissolved in phosphate buffer pH 7.5 (0.05 M, 1.0 mL) and cooled to 4 • C [34,35]. N-Hydroxysuccinimide ester derivative (18)(19)(20) (0.05 mmol) in DMF (1.5 mL) was added dropwise. The reaction mixture was stirred between 2 and 7 • C for 12-24 h. The reaction mixture was transferred to dialysis tubing and dialysed against stirred, distilled water (500 times the initial volume).…”

“…However, it has been shown [16][17][18][19][20][21][22][23][24][25][26][27][28] that these steroids undergo extensive metabolism in horses, cattle and humans, such that little parent steroid is excreted in the urine. Commonly, phase I metabolites result from hydroxylation of the steroid, as well as A-ring reductions.…”