John Wiley & Sons, Ltd.

Rates and product identification for trenbolone acetate metabolite biotransformation under aerobic conditions

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Trenbolone acetate (TBA) metabolites are endocrine active contaminants discharged into the aquatic environment in runoff from agricultural fields, rangelands, and concentrated animal feeding operations (CAFOs). To investigate the environmental fate of these compounds and their biotransformation mechanisms, we used inocula from a variety of different water sources and dosed biologically active microcosms with ~1,400 ng/L of TBA metabolites, including 17β‐trenbolone (17β‐TBOH), trendione (TBO), and 17α‐trenbolone (17α‐TBOH). To investigate aerobic biotransformation rates and interconversions between known TBA metabolites, GC‐MS/MS was used to measure concentrations and assess product distributions as a function of time. High resolution LC‐MS/MS was used to characterize novel transformation products and potential transformation pathways. Kinetic analysis yields observed half‐lives of approximately 0.9, 1.3, and 2.2 days for 17β‐TBOH, TBO, and 17α‐TBOH, respectively, at 20oC, although colder conditions increased half‐lives to 8.5 days and biphasic transformation was observed. Relative to reported faster attenuation rates in soils, TBA metabolites are likely more persistent in aqueous systems. Product distributions indicate an enzymatic preference for biotransformation between TBO and 17β‐TBOH. LC‐MS/MS characterization indicates dehydrogenation products as the major detectable products and demonstrates that major structural elements responsible for bioactivity in steroids are likely retained during biotransformation. This article is protected by copyright. All rights reserved

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