Analytical Sciences

Characterization and Quantification of Fluoxymesterone Metabolite in Horse Urine by Gas Chromatography/Mass Spectrometry

Masayuki YAMADA,* Sugako ARAMAKI,* Tomoo HOSOE,** Masahiko KUROSAWA,* Isao KIJIMA-SUDA,* Koichi SAITO,** and Hiroyuki NAKAZAWA**

*Laboratory of Racing Chemistry, 1731-2 Tsuruta, Utsunomiya 320-0851, Japan
**Faculty of Pharmaceutical Sciences, Hoshi University, 2-4-41 Ebara, Tokyo 142-8501, Japan

Fluoxymesterone, an anabolic steroid with the 17α-methyl,17β-hydroxy group, has been developed as an oral formulation for therapeutic purposes. However, it is also used illegally in racehorses to enhance racing performance. In this study, we detected 9α-fluoro-17,17-dimethyl-18-norandrostane-4,13-dien-11β-ol-3-one by gas chromatography/mass spectrometry (GC/MS), which has not been reported as a fluoxymesterone metabolite so far in horse. It was synthesized for use as a reference standard, and characterized on the basis of ¹H NMR and ¹³C NMR spectra, as well as GC/MS EI mass spectra of TMS derivatives. It was excreted as the main metabolite in horse urine, and its reference standard could be synthesized easily. Therefore, this metabolite could be a useful target for a doping test of fluoxymesterone in racehorses.

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