title: UV-photodegradation of desipramine: Impact of concentration, pH and temperature on formation of products including their biodegradability and toxicity.
abstract: Desipramine (DMI) is a widely used tricyclic antidepressant, and it is the major metabolite of imipramine (IMI) and lofepramine (LMI); IMI and LMI are two of the most commonly used tricyclic antidepressants. If DMI enters the aquatic environment, it can be transformed by the environmental bacteria or UV radiation. Therefore, photolysis of DMI in water was performed using a simulated sunlight Xenon-lamp and a UV-lamp. Subsequently, the biodegradability of DMI and its photo-transformation products (PTPs) formed during its UV photolysis was studied. The influence of variable conditions, such as initial DMI concentration, solution pH, and temperature, on DMI UV photolysis behavior was also studied. The degree of mineralization of DMI and its PTPs was monitored. A Shimadzu HPLC-UV apparatus was used to follow the kinetic profile of DMI during UV-irradiation; after that, ion-trap and high-resolution mass spectrometry coupled with chromatography were used to monitor and identify the possible PTPs. The environmentally relevant properties and selected toxicity properties of DMI and the non-biodegradable PTPs were predicted using different QSAR models. DMI underwent UV photolysis with first-order kinetics. Quantum yields were very low. DOC values indicated that DMI formed new PTPs and was not completely mineralized. Analysis by means of high-resolution mass spectrometry revealed that the photolysis of DMI followed three main photolysis pathways: isomerization, hydroxylation, and ring opening. The photolysis rate was inversely proportional to initial DMI concentration. The pH showed a significant impact on the photolysis rate of DMI, and on the PTPs in terms of both formation kinetics and mechanisms. Although temperature was expected to increase the photolysis rate, it showed a non-significant impact in this study. Results from biodegradation tests and QSAR analysis revealed that DMI and its PTPs are not readily biodegradable and that some PTPs may be human and/or eco-toxic, so they may pose a risk to the environment.
authors.affiliation: Sustainable Chemistry and Material Resources, Institute of Sustainable and Environmental Chemistry, Leuphana University of Lüneburg, Scharnhorststraße 1 C13, DE 21335 Lüneburg, Germany; Pharmaceutical Analytical Chemistry Department, Faculty of Pharmacy, Suez Canal University, Ismailia 41522, Egypt.
authors.forename: Nareman D H
authors.initials: NDH
authors.lastname: Khaleel
authors.affiliation: Sustainable Chemistry and Material Resources, Institute of Sustainable and Environmental Chemistry, Leuphana University of Lüneburg, Scharnhorststraße 1 C13, DE 21335 Lüneburg, Germany; Pharmaceutical Analytical Chemistry Department, Faculty of Pharmacy, Suez Canal University, Ismailia 41522, Egypt.
authors.forename: Waleed M M
authors.initials: WMM
authors.lastname: Mahmoud
authors.affiliation: Sustainable Chemistry and Material Resources, Institute of Sustainable and Environmental Chemistry, Leuphana University of Lüneburg, Scharnhorststraße 1 C13, DE 21335 Lüneburg, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Olsson
authors.affiliation: Sustainable Chemistry and Material Resources, Institute of Sustainable and Environmental Chemistry, Leuphana University of Lüneburg, Scharnhorststraße 1 C13, DE 21335 Lüneburg, Germany. Electronic address: klaus.kuemmerer@leuphana.de.
authors.forename: Klaus
authors.initials: K
authors.lastname: Kümmerer
mesh_terms: D000929:Antidepressive Agents, Tricyclic / Q000737:chemistry* / Q000528:radiation effects; D001419:Bacteria / Q000187:drug effects; D001673:Biodegradation, Environmental; D002853:Chromatography, Liquid; D003891:Desipramine / Q000737:chemistry* / Q000528:radiation effects; D004305:Dose-Response Relationship, Drug; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D013058:Mass Spectrometry; D010782:Photolysis; D021281:Quantitative Structure-Activity Relationship; D013696:Temperature; D018675:Toxicity Tests; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000737:chemistry* / Q000528:radiation effects
chemical_list: D000929:Antidepressive Agents, Tricyclic; D014874:Water Pollutants, Chemical; D003891:Desipramine
keywords: CBT and MRT; Mineralization; Photo-transformation product; QSAR; Tricyclic antidepressants