In vitro synthesis and characterisation of three fenoterol sulfoconjugates detected in fenoterol post-administration urine samples

摘要

Fenoterol, a fast-acting β2-adrenergic agonist, is used in the therapy of obstructive pulmonary diseases and for the inhibition of premature labour obstetrics. Doping control for β2-agonists, which are prohibited in sports by the World Anti-Doping Agency, is commonly performed by liquid chromatography/mass spectrometry after hydrolysis of phase II metabolites. The continuing development of analytical procedures has led to direct injection of urine samples without sample preparation becoming a viable tool. For the detection of substances without sample preparation, including hydrolysis, detailed information of the phase II metabolism of the substances is essential. In this study, human S9 fractions of different tissues and two recombinant sulfotransferases were investigated for their potential to form fenoterol sulfoconjugates, which were characterised in detail. Two mono-sulfoconjugates and one bis-sulfoconjugate were synthesised and their structures confirmed by liquid chromatography–high-resolution/high-accuracy mass spectrometry. All of the metabolites were identified as esterified phenolic compounds. Excretion studies with orally and inhalatively administered fenoterol proved the occurrence of the sulfoconjugates in vivo. Inhalatively administered fenoterol resulted in the detection of the two mono-sulfoconjugates in low amounts in urine due to the lower inhalation dose of fenoterol compared to the oral dose. After oral uptake of fenoterol, the two mono-sulfoconjugates and a fenoterol bis-sulfoconjugate were detected in urine. This is the first report of the bis-sulfoconjugate.