Evaluation of pranoprofen photodegradation induced by ultraviolet-light irradiation in aqueous media

The photodegradation of pranoprofen (PP), which is a member of the 2-arylpropionic acid family of non-steroidal anti-inflammatory drugs, in aqueous media under ultraviolet light (UV) irradiation was studied herein. Our purpose is to clarify the photostability and photochemical behavior of PP. The photodegradation of PP and the generation of its photoproducts were monitored by means of high-performance liquid chromatography (HPLC). PP was degraded completely after 2h of UV irradiation with the generation of several photoproducts identified in HPLC analysis. The chemical structures of nine PP photoproducts were elucidated based on the mass/charge ratio (m/z) values and fragmentation patterns of protonated ions obtained from electrospray ionization liquid chromatography mass spectrometry (ESI-LC/MS/MS). Among these nine PP photoproducts, the main product was 7-acetyl-5H-[1]benzopyrano[2,3-b]pyridin-5-one, which was the final oxidized form of PP. The photodegradation pathways are proposed, showing that oxidation of excited PP might be an initial process. This is the first study showing the photochemical behavior of PP, and these results allow further research focused on the photostability of PP in commercial tablets and its changed formulation, the toxicological potencies of photoproducts and photostabilization approaches.