Cis-Trans Isomerization Reaction of Sulindac Induced by UV Irradiation in the Aqueous Media

Abstract

Photodegradation of sulindac (SL), which is clinically used as an anti-inflammatory, analgesic and antipyretic drug in an aqueous media under the ultraviolet (UV) irradiation was investigated. Degradation of SL and the generation of the photoproduct were monitored by means of high-performance liquid chromatography (HPLC). Residual amount of SL was decreased after UV-A, -B and -C irradiation with the generation of the photoproduct, but kinetics of degradation of SL and generation of the photoproduct seems to reach the equilibrium under only the UV-A irradiation. Based on the nuclear overhauser effect spectroscopy (NOESY) coupling pattern in nuclear magnetic resonance (NMR) spectrum and fragmentation pattern in electrospray ionization time-of-flight mass spectrometry (ESI-TOF/MS/MS), the photoproduct was identified as the trans-isomer of SL and the main pathway of SL photo-conversion was photoisomerization by the UV-A irradiation. Monitoring the degradation of SL and its photoproduct by the UV irradiation indicated that photochemical reaction of SL induced by the UV-A irradiation, which is photoisomerization, is different from that of induced by the UV-B or the UV-C irradiation, which is probably further degradation but there was no identification that a further photoproduct was generated from the initially formed photoproduct in the result of HPLC analysis. This is the first study showing the photoisomerization of SL induced by the UV irradiation in the aqueous media.