Environmental photochemistry of dienogest: phototransformation to estrogenic products and increased environmental persistence via reversible photohydration

Nicholas C. Pflug, Madeline K. Hankard, Stephanie M. Berg, Meghan O’Connor, James B. Gloer, Edward P. Kolodziej, David M. Cwiertny, Kristine H. Wammer
In: Environmental Science: Processes & Impacts · 2017 · vol. 19(11) , pp. 1414–1426 · doi:10.1039/c7em00346c · PMID:29034382 · W2762314890
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⚙ AI-generated summary by claude@2026-06, 2026-06-10 ⓘ

Phototransformation of dienogest in water produces estrogenic compounds and persistent photohydrates that revert to the parent compound, increasing its potential environmental and endocrine risks.

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⚙ AI-generated deep summary by claude@2026-06, 2026-06-10 · read from full text ⓘ

This paper investigated the environmental photolysis of dienogest, using high-resolution mass spectrometry and 1D/2D nuclear magnetic resonance to identify phototransformation products across pH 2–7. Dienogest underwent rapid direct photolysis (half-life ~1–10 minutes), yielding complex mixtures that included three photohydrates accounting for ~80% of converted mass at pH 7; these photohydrates were reversible and returned to parent dienogest in the absence of light. The authors also detected two estrogenic compounds formed via A-ring aromatization, indicating that photochemical transformation can increase estrogenic activity in the product mixture, and they noted that some products had different nuclear receptor binding capabilities than dienogest. This paper is centrally about endometriosis—adenomyosis relevance: dienogest is a clinically used progestin associated with endometriosis/adenomyosis treatment, and the study’s findings on endocrine-active photoproducts bear directly on those conditions’ hormonal milieu.

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Abstract

∼ 1-10 min), forming complex photoproduct mixtures across the pH range examined (pH 2 to 7). Identified products include three photohydrates that account for ∼80% of the converted mass at pH 7 and revert back to parent dienogest in the absence of light. Notably, we also identified two estrogenic compounds produced via the A-ring aromatization of dienogest, evidence for a photochemically-induced increase in estrogenic activity in product mixtures. These results imply that dienogest will undergo complete and facile photolytic transformation in sunlit surface water, yet exhibit greater environmental persistence than might be anticipated by inspection of kinetic rates. Photoproduct mixtures also include transformation products with different nuclear receptor binding capabilities than the parent compound dienogest. These outcomes reveal a dynamic fate and biological risk profile for dienogest that must also take into account the composition and endocrine activity of its transformation products. Collectively, this study further illustrates the need for more holistic regulatory, risk assessment, and monitoring approaches for high potency synthetic pharmaceuticals and their bioactive transformation products.
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Environmental photochemistry of dienogest: phototransformation to estrogenic products and increased environmental persistence via reversible photohydration† Abstract Potent trienone and dienone steroid hormones undergo a coupled photohydration (in light)-thermal dehydration (in dark) cycle that ultimately increases their environmental persistence. Here, we studied the photolysis of dienogest, a dienone progestin prescribed as a next-generation oral contraceptive, and used high resolution mass spectrometry and both 1D and 2D nuclear magnetic resonance spectroscopy to identify its phototransformation products. Dienogest undergoes rapid direct photolysis (t1/2 ∼ 1–10 min), forming complex photoproduct mixtures across the pH range examined (pH 2 to 7). Identified products include three photohydrates that account for ∼80% of the converted mass at pH 7 and revert back to parent dienogest in the absence of light. Notably, we also identified two estrogenic compounds produced via the A-ring aromatization of dienogest, evidence for a photochemically-induced increase in estrogenic activity in product mixtures. These results imply that dienogest will undergo complete and facile photolytic transformation in sunlit surface water, yet exhibit greater environmental persistence than might be anticipated by inspection of kinetic rates. Photoproduct mixtures also include transformation products with different nuclear receptor binding capabilities than the parent compound dienogest. These outcomes reveal a dynamic fate and biological risk profile for dienogest that must also take into account the composition and endocrine activity of its transformation products. Collectively, this study further illustrates the need for more holistic regulatory, risk assessment, and monitoring approaches for high potency synthetic pharmaceuticals and their bioactive transformation products. - This article is part of the themed collection: Editor’s Choice: Aquatic Photochemistry

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