Ebastine

Ebastine (EB) is a second-generation histamine H₁ receptor antagonist and utilized for the relief of allergy symptoms. In this study, the photodegradability of EB in an aqueous media was evaluated and the chemical structures of generated photoproducts were elucidated. EB photodegradation was monitored using high-performance liquid chromatography (HPLC), and two EB photoproducts were observed in HPLC chromatograms along with the decrease of EB contents in sample solutions. To elucidate their chemical structures, electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) analysis was carried out. From the mass to charge ratio values of molecular ion peaks and the fragmentation patterns, two EB photoproducts were designated as benzophenone and 4'-tert-butylacetophenone, respectively. Moreover, for the better understanding of EB photodegradation, photodegradation pathways of EB were speculated based on the structures of photoproducts. The photodegradation pathways of EB seemed to be an oxidative elimination of diphenyl methylene moiety and a Norrish type Ⅱ reaction. Finally, in silico toxicity prediction was performed for the estimation of toxicological potencies of EB photoproducts, suggesting the nature of EB might be changed by the photodegradation. In conclusion, two novel EB photoproducts were clarified and their formation mechanisms were proposed, which might make it possible to the better understanding of EB photodegradability.