Laccase-Mediated Transformation of Trazodone Hydrochloride and Its By-Products

The increasing drug consumption worldwide raises environmental and health concerns, as pharmaceutical residues entering the environment pose risks to both ecosystems and human health. Enzyme remediation has been emerging in recent decades as a possible solution to eliminate recalcitrant pharmaceutical pollutants in wastewater or contaminated sites, offering a faster alternative to microbial remediation, e.g., without the need for microbial growth or adaptation. Moreover, enzymes operate under a wider range of conditions, avoiding biomass formation and disposal, and antibiotic resistance risks. In the present study, high amounts (up to 5000 mg/L) of trazodone hydrochloride and its by-products, namely Impurity H and Compound F, were enzymatically treated using a laccase-mediator system consisting of the laccase from Trametes hirsuta (ThL) and the mediator 1-hydroxybenzotriazole (HBT). Different concentrations of an organic solvent system composed of acetone and isobutyl alcohol in a 1:1 ratio and up to 20% (v/v) were employed to simulate the matrix of a real industrial production waste stream. Thereby, the enzymatic oxidation of trazodone hydrochloride and its by-products was not significantly affected by the varying solvent concentrations, resulting in maximum conversions of 62%, 73% and 62% of trazodone hydrochloride, impurity H, and impurity F, respectively. Liquid chromatography—high-resolution mass spectrometry (LC-HRMS) indicated preferential oxidation of the piperazine group in all three molecules. In vivo ecotoxicity experiments must be carried out in the future to assess the toxicological and environmental behaviour of the obtained degradation products. This work emphasised the potential role of enzymes in supporting the transition towards a more sustainable pharmaceutical industry.