Biotransformation Pathways of Biocides and Pharmaceuticals in Freshwater Crustaceans Based on Structure Elucidation of Metabolites Using High Resolution Mass Spectrometry

Abstract

So far, there is limited information on biotransformation mechanisms and products of polar contaminants in freshwater crustaceans. In the present study, metabolites of biocides and pharmaceuticals formed in Gammarus pulex and Daphnia magna were identified using liquid chromatography-high resolution mass spectrometry. Different confidence levels were assigned to the identification of metabolites without reference standards using a framework based on the background evidence used for structure elucidation. Twenty-five metabolites were tentatively identified for irgarol, terbutryn, tramadol, and venlafaxine in G. pulex (21 via oxidation and 4 via conjugation reactions) and 11 metabolites in D. magna (7 via oxidation and 4 via conjugation reactions), while no evidence of metabolites for clarithromycin and valsartan was found. Of the 360 metabolites predicted for the four parent compounds using pathway prediction systems and expert knowledge, 23 products were true positives, while 2 identified metabolites were unexpected products. Observed oxidative reactions included N- and O-demethylation, hydroxylation, and N-oxidation. Glutathione conjugation of selected biocides followed by subsequent reactions forming cysteine conjugates was described for the first time in freshwater invertebrates.

How Biotransformation Influences Toxicokinetics of Azole Fungicides in the Aquatic Invertebrate Gammarus pulex

“…All samples were analyzed by online solid phase extraction coupled to liquid chromatography high resolution tandem mass spectrometry (online-SPE-LC-HRMS/MS). 26 Automated online-SPE served for sample cleanup and enrichment. By using a mixed bed multilayer cartridge, a broad range of compounds with different polarities, molecular sizes, and charges was retained and enriched.…”

Untargeted Metabolomics Strategies—Challenges and Emerging Directions

“…In 2007 the Chemical Analysis Working Group (CAWG) of the Metabolomics Standards Initiative (MSI) published a first stage of guidelines for reporting the minimum metadata relative to metabolite identification as a means to communicate the confidence of identifications [27]. Recently, revisions to these levels have been proposed to cover special cases where level determination may be unclear [28, 29]. We propose modest changes to include orthogonal IM-MS data as evidence for metabolite identification (Figure 3).…”

Comparative metabolism as a key driver of wildlife species sensitivity to human and veterinary pharmaceuticals

“…Nonetheless, as molecular and biochemical methods have advanced, there is growing evidence of both Phase I and II enzyme activity in fish [21,27,28] and recent studies have addressed how dietary and trophic variables may affect enzyme activity in fish [29]. There are also a growing number of studies on the metabolism of pharmaceuticals in fish [30][31][32][33][34][35][36][37][38][39][40] and to a far lesser extent invertebrates [41]. Veterinary pharmaceuticals have also been studied from a comparative metabolism perspective [42,43].…”