Fenamidone Metabolite

In this study, fenamidone, propamocarb and their transformation products were monitored in cherry tomato, cucumber, and courgette samples. A mixture of both compounds, which have different physico-chemical characteristics, are commercially available (Consento®). For analysis, ultra high-performance liquid chromatography coupled to Orbitrap mass spectrometry (UHPLC-Orbitrap-MS) and gas chromatography coupled to Q-Orbitrap mass spectrometry (GC-Q-Orbitrap-MS) were used. The dissipation of these active ingredients was monitored at two doses (normal and double dose) from 1 to 40 days after the application of the commercial product. Half-lives (DT50) were lower than 30 days for both compounds, which indicates low persistence. Metabolites of both compounds were also monitored due to in some cases these can be more dangerous for human health than the parent compounds. The metabolites monitored were RPA 410193 ((5S)-3-anilino-5-methyl-5-phenylimidazolidine-2,4-dione), acetophenone, 2-phenylpropionic acid, 5-methyl-5-phenylhydantoin and 5-methylhydantoin for fenamidone, and propamocarb hydrochloride (propyl 3-(dimethylamino)propylcarbamate hydrochloride), N-oxide propamocarb (propyl [3-(dimethylnitroryl)propyl]carbamate), oxazoline-2-one propamocarb (3-[3-(dimethylamino)propyl]-4-hydroxy-4-methyl-1,3-oxazolidin-2-one), 2-hydroxypropamocarb and n-desmethyl propamocarb (propyl [3-(methylamino)propyl]carbamate) for propamocarb. In addition, they were detected one day after the application of commercial product, being RPA 410193, the metabolite detected at the highest concentration in samples. Retrospective analysis of incurred samples allowed putative identification of four possible new metabolites of propamocarb and one of fenamidone.

A fenamidone and propamocarb dissipation study was carried out applying ultra high-performance liquid chromatography coupled to Orbitrap mass spectrometry (UHPLC-Orbitrap-MS). Dissipation kinetics were evaluated in different types of soils and in water under different conditions (sunlight or darkness). In addition, a plant protection product containing both compounds was applied at two doses: (i) single and (ii) double dose in soils, and (i) single and (ii) fivefold dose in water. The fenamidone and propamocarb concentration decreased during the monitored period (100 days), obtaining high persistence in the case of water studies (DT50> 50 days) and low to medium persistence in soils (DT50< 50 days). No Observed Effect Concentration (NOEC) and concentration causing 50% lethality (EC50) were calculated and showed that fenamidone could cause toxic effects in soil and water organisms due to very high NOEC values (0.013 mg/L for aquatic invertebrates) while propamocarb did not cause any lethality. Fenamidone and propamocarb metabolites were also monitored with acetophenone and RPA-411639 ((5)-5-methyl-2-(methylthio)-3-(4-S nitrophenyl)amino-5-phenyl-3,5-dihydro-4H-imidazole-4-one) being the main metabolites for fenamidone. These metabolites obtained concentration values of up to 25% initial fenamidone content which can be a risk for the environment and fauna but, despite the toxicity of these compounds, they have not been studied yet. Metabolite 175 m/z and propamocarb n-desmethyl were the main propamocarb metabolites with values of 3% of initial propamocarb content. Three new propamocarb metabolites were detected in water samples and one in soil, highlighting the capabilities of the proposed methodology for monitoring known metabolites and identifying new ones in environmental studies.

Liver S9 fractions from common carp (Cyprinus carpio) and rainbow trout (Oncorhynchus mykiss) were incubated with seven pesticides (fenamidone, fenoxaprop-p-ethyl, penflufen, spirotetramat, tebuconazole, tembotrione and trifloxystrobin) and the metabolic pathways of the applied chemicals were determined by HPLC-high-resolution mass spectrometry. Five of the seven pesticides (fenamidone, penflufen, spirotetramat, trifloxystrobin and fenoxaprop-p-ethyl) revealed a higher metabolic capacity of rainbow trout liver fractions compared to carp liver fractions. The other two pesticides (tebuconazole and tembotrione) showed a similar and marginal biotransformation for liver S9 fractions of both species. Furthermore, four compounds (penflufen, spirotetramat, tembotrione and tebuconazole) were incubated with cryo-preserved hepatocytes of rainbow trout showing additional conjugated metabolites compared to liver S9 fractions. The incubations were performed with concentrations of 1 and 10 μM for experiments with liver S9 fractions and 5 μM with hepatocytes for up to 120 (liver S9 fractions) or 240 min (hepatocytes). A set of positive controls was used to confirm the metabolic capability of the in vitro systems. The comparison of the in vitro results from hepatocyte assays of penflufen and tebuconazole with the data from corresponding in vivo studies performed according to OECD (Organisation for Economic Co-operation and Development) guideline 305 exhibited a similar metabolic behavior for these pesticides and emphasizes the reliability of the in vitro assays. Besides investigation of the metabolism of plant protection products for research purposes, inter-species comparison by in vitro assays and the use of PBTK modelling approaches will allow improved environmental and dietary risk assessments.