Metabolites of trenbolone acetate (TBA), a growth promoter used in animal agriculture, rapidly undergo direct photolysis to yield products that are photostable but prone to other, non-photochemical transformation pathways. Here, we show that the dominant photoproduct, a variant of trenbolone hydroxylated at the C12 position of the steroid ring, is unstable in the absence of light and readily undergoes hydrolysis or dehydration. Notably, dehydration represents a viable pathway for regeneration of the parent TBA metabolite in surface waters, effectively making their loss via direct photolysis reversible. While observed for all TBA metabolites, photoproduct-to-parent reversion occurs most readily for 17a-trenbolone (17a-TBOH), allowing as much as 80-90% of the initial metabolite mass to be regenerated over several days in the dark. Consistent with known steroid chemistry, dehydration is acid-catalyzed for all metabolites, but base-catalyzed only for 17a-TBOH. Dehydration is also strongly temperature dependent, occurring most rapidly at high temperature (35 �C). The observation of coupled photolysis and dehydration has significant implications, causing TBA metabolites to be far more persistent in surface waters than is currently realized. Further, their persistence should also exhibit diurnal and seasonal cycles, as well as a dependence on pH. Outcomes also call into question all current occurrence data for TBA metabolites, as many aspects of sample collection, handling and processing are likely to influence the rate and extent of this dehydration reaction.

Photoproduct-to-parent reversion for trenbolone acetate metabolites: An unrecognized route to endocrine disruption in agriculturally impacted surface waters?

246th National Meeting (2013)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.