Comprehensive Study of Antidepressants and Benzodiazepines in Environmental Matrices: Chiral Biodegradation and Analytical Method Development

Abstract

A number of drugs, including antidepressants and benzodiazepines, are currently of environmental concern due to their widespread use and presence in aquatic ecosystems. This thesis initially focuses on the environmental literature associated with their pharmacology, physicochemical properties, chiral impact, and methods of extraction and analysis. The persistence of these compounds in the environment raises significant concerns about their potential ecological consequences. Understanding their enantiomeric compositions and environmental fates is crucial, as enantiomers can exhibit differing toxicity, bioactivity, and persistence. Environmental studies have consistently revealed the presence of these compounds in various ecosystems, where they can adversely affect aquatic organisms and disrupt the food chain. To accurately quantify these pharmaceuticals in environmental samples, advanced extraction and analysis methods, such as solid-phase extraction (SPE) and liquid chromatography-mass spectrometry (LC-MS), are essential. Chiral chromatographic separations were performed for antidepressants and benzodiazepines, with adjustments to mobile phase conditions, such as buffer pH and ethanol content, proving beneficial for enantiomeric resolution. However, further research is needed to achieve optimal separation for all compounds. The biodegradation of these pharmaceuticals in wastewater systems was also investigated, revealing the critical role of microbial activity in their degradation. The study emphasized the importance of characterizing microbial communities, as they are central to understanding the environmental fate and stereoselective transformations of chiral pharmaceuticals. The investigation into benzodiazepines, including diazepam, oxazepam, temazepam, and etizolam, highlighted their biodegradability and transformation pathways. Microbial-mediated biodegradation was found to be a vital process in reducing the concentrations of these compounds, with abiotic degradation pathways also contributing to their overall breakdown. Key factors such as pH, temperature, microbial activity, and co-occurring contaminants were shown to influence their degradation dynamics. These findings underscore the importance of optimizing wastewater treatment systems to mitigate the environmental and human health risks associated with benzodiazepine contamination. Similarly, the study of antidepressants, such as fluoxetine and venlafaxine, revealed efficient biodegradation pathways driven by microbial activity, with stereoselective processes influencing the degradation of individual enantiomers. The impact of environmental parameters, such as pH and dissolved oxygen levels, on microbial efficiency was highlighted, along with the identification of bacterial taxa capable of metabolising these compounds. These findings demonstrate the critical role of microbial consortia in the removal of antidepressants from wastewater, with implications for reducing their ecological footprint and ensuring the safety of aquatic ecosystems.