An in vitro study on metabolism of 17β-boldenone and boldione using cattle liver and kidney subcellular fractions

17β-Boldenone (17β-BOLD) and Boldione (ADD) are steroid compounds with androgenic activity, likely to be used as growth promoters in cattle. Different studies still on-going aiming to distinguish between “natural” occurrence or illegal BOLD source had already indicated that their metabolism in cattle is of relevant significance. To identify metabolites as in vivo markers to support the thesis of exogenous administration, a further approach to the in vitro biotransformation of 17β-BOLD and ADD was performed using different subcellular fractions obtained from both liver and kidney of untreated cattle. Polar and non-polar metabolites obtained from incubated parent compounds were formerly separated by high performance liquid chromatography (HPLC) elution and successively identified by liquid chromatography tandem mass spectrometry (LC–MS/MS) detection.The bovine liver was the target tissue of the main metabolic reaction transforming 17β-BOLD to ADD and vice versa. The presence of 6β-hydroxy-17β-BOLD, produced from both compounds when NADPH was added as cofactors to liver post mitochondrial and microsomal fractions suggests that cytochrome P450-dependent enzymes could be involved in the biotransformation, as it occurs for 6β-hydroxylation of 17β-testosterone. The results indicated that the urinary excretion profile in vivo of 6β-hydroxy-17β-BOLD and 16α-hydroxy-17β-BOLD could be studied together with 17α- and 17β-BOLD as putative markers of BOLD treatment in cattle.