Unveiling the photodegradation of tralkoxydim herbicide and its formulation in natural waters: Structural elucidation of transformation products and toxicity assessment

Pesticide degradation products (DPs), as emerging contaminants, are being detected in aquatic environments due to the widespread use of their active substances and pose potential risks to aquatic ecology and human health. However, their identification is challenging due to the many environmental conditions that influence their degradation processes. The photodegradation of the herbicide tralkoxydim and its formulation has been studied in ultrapure, spring and river waters and has shown rapid degradation. The photodegradation of tralkoxydim was slower in natural water and in the presence of humic acids (HA) than in ultrapure water, with half-lives of 5.1 h for river water and 1.1 h for ultrapure water. For the first time, three degradation products were identified in aquatic media using HPLC-TOF-MS/MS. These include photoisomerization, photolysis of the N-O bond of the oxime resulting in the tralkoxydim imine (major DP), and cyclization leading to tralkoxydim oxazole. Quantitative structure-activity relationship (QSAR) models were employed to approximate the potential ecotoxicological and environmental impacts of tralkoxydim and its DPs. Additionally, the toxicity of the isolated DPs was evaluated using a standard microtest bioassay with Vibrio fischeri bacteria. The results show that tralkoxydim imine and tralkoxydim oxazole exhibit high toxicity.

Kinetic study, byproducts characterization and photodegradation pathway of profoxydim in a biochar water soil system

The study focused on the photodegradation of profoxydim, a low-toxicity cyclohexanedione herbicide commonly used in rice crops, under simulated sunlight conditions. Profoxydim's behavior in paddy field conditions is not well understood, and this research aimed to fill that gap, particularly examining the effect of commonly utilized organic amendments such as biochar (BC) on its degradation. Results indicated that profoxydim degrades rapidly, with a half-life of 2.4 ± 0.3 h in paddy water and 1.03 ± 0.1 h in paddy soil. However, when BC was introduced, the degradation slowed significantly, extending the half-lives to 3.1 ± 0.2 h in water and 3.07 ± 0.5 h in soil. The study identified five degradation products (DPs) using TOF mass accuracy measurements and MS/MS spectra fragmentation. Two of these DPs were found to be more stable than profoxydim itself. Additionally, the research proposed a novel photodegradation pathway, highlighting processes such as homolytic C-N bond cleavage, photoisomerization, and photoinduced oxidation. The study's findings contribute new insights into the environmental fate of profoxydim, offering a deeper understanding of its transformation in rice paddy fields and aiding in the assessment of potential risks associated with its residues in agricultural environments.

Preparation and Characterization of Indomethacin Supramolecular Systems with β-Cyclodextrin in Order to Estimate Photostability Improvement

Cyclodextrins have found wide application in contemporary chemistry, pharmacy and medicine. Because of their unique properties, cyclodextrins are constantly used in research on solubility or stability improvement, as well as other physicochemical properties of medicinal substances. Indomethacin (IND) is a photolabile molecule that also attracts the interest of researchers due to its therapeutic potential and the need to overcome its problematic photosensitivity. Supramolecular complexes of indomethacin with β-cyclodextrin (CD) are already known, and they show greater stability compared to complexes with other types of cyclodextrins. So far, however, the sensitivity to light of physical mixtures and inclusion complexes in the solid phase has not been studied, and their various stoichiometries have not yet been investigated. Due to this fact, the aim of the present study is to obtain supramolecular systems (inclusion complexes and physical mixtures) of indomethacin with three different amounts of β-cyclodextrin. Assessment of the photochemical stability of indomethacin-β-cyclodextrin systems in the solid state is performed in order to find the best correlation between IND stability and the amount of CD. Comparative analysis of physicochemical degradation for stoichiometry systems [CD:IND] = [1:1], [0.5:1] and [0.1:1] is performed by using ultraviolet spectroscopy, transmission—FTIR, reflection—ATR-FTIR infrared spectroscopy and DSC calorimetry.

Current regulatory requirements and practical approaches for stability analysis of pharmaceutical products: A comprehensive review

Different regulatory guidelines recommend establishing stability profile of pharmaceuticals at the time of drug development. The expiry date, retesting period and storage conditions of active drugs or products are established through stability analysis. Several regulatory guidelines exist for stability testing of pharmaceuticals. Mostly, ICH stability guidelines are followed in practice. This guideline recommends to validate stability indicating method using forced degradation samples that contains all possible degradation impurities. ICH guidelines provide general recommendations for inclusion of stability indicating parameters in a stability testing protocol. However, those guidelines do not provide specific requirements and experimental methodology to be followed for stability studies. Due to this gap, often confusion arises in the scientific community in designing stability testing protocol. Therefore, significant variations are observed in reported literature in selection of stability indicating parameters. Procedural dissimilarity amongst reported stability studies is also evident. This review discusses the regulatory guidelines and procedures to follow in performing stability testing of pharmaceuticals. Scope of this review also includes recommendations on practical approaches for designing stability testing protocol to fulfill current regulatory requirements for drug substances and their formulations.

Studies on photodegradation process of psychotropic drugs: a review

Consumption of psychotropic drugs is still increasing, especially in high-income countries. One of the most crucial consequences of this fact is significant release of them to the environment. Considerable amounts of atypical antipsychotics, benzodiazepines, antidepressants, and their metabolites were detected in river, lake, and sea water, as well as in tissues of aquatic organisms. Their ecotoxicity was proved by numerous studies. It should be noticed that interaction between psychotropic pharmaceuticals and radiation may lead to formation of potentially more toxic intermediates. On the other hand, photo-assisted wastewater treatment methods can be used as an efficient way to eliminate them from the environment. Many methods based on photolysis and photocatalysis were proposed and developed recently; nevertheless, the problem is still unsolved. However, according to recent studies, photocatalysis could be considered as the most promising and far more effective than regular photolysis. An overview on photolytic as well as homogenous and heterogeneous photocatalytic degradation methods with the use of various catalysts is presented. The photostability and phototoxicity of pharmaceuticals were also discussed. Various analytical methods were used for the photodegradation research, and this issue was also compared and summarized. Use of high-resolution multistage mass spectrometry (Q-TOF, ion trap, Orbitrap) was suggested. The combined techniques such as LC-MS, GC-MS, and LC-NMR, which enable qualitative and quantitative analyses in one run, proved to be the most valuable in this case. Assembling of MS/MS spectra libraries of drug molecules and their phototransformation products was identified as the future challenge.

Characterization of forced degradation products of clozapine by LC-DAD/ESI-Q-TOF

Forced degradation of clozapine in solutions under acidic, basic, neutral, photo UV-vis, photo UVC and oxidative stress conditions was investigated and structural elucidation of its degradation products was performed with the use of the UHPLC-DAD system coupled with accurate hybrid ESI-Q-TOF mass spectrometer. The developed method allows to collect all essential data for the determination of degradation kinetics and for the structural elucidation of the formed products. Six degradation products were found and their masses and formulas were obtained with high accuracy (0.61-3.75ppm). For all the analyzed compounds MS/MS fragmentation spectra were also obtained allowing structural elucidation of the unknown degradation products. It was found that the decomposition of clozapine yields the first-order kinetic reaction in all stress conditions and it is fragile towards acidic hydrolysis and oxidative conditions. Additionally, PCA analysis of registered TOF (MS) forced degradation profiles of clozapine shows no differences between the samples obtained from pharmaceutical formulation and bulk substance.