Identification of Metabolites of the Fungicide Penconazole in Human Urine

Abstract

Penconazole (PEN) is a fungicide used in agriculture that has been classified as hazardous to humans and the environment. The objective of this work was to identify PEN urinary metabolites in humans and propose a biomarker for PEN exposure. Five urine samples were collected from agricultural workers who worked with and were exposed to PEN. Samples were analyzed by liquid chromatography coupled with hybrid triple quadrupole-linear ion trap mass spectrometry, with the source operating in the electrospray ionization mode. Metabolites previously identified in animal studies were searched as possible metabolites in humans. Candidate metabolites were first identified by multiple reaction monitoring following the protonated molecular ions that generated the protonated triazole moiety, which is expected to be present in all PEN metabolites; second, the isotopic patterns of the molecular ions were checked for consistency with the presence of two chlorine atoms; third, the full mass spectra were evaluated for consistency with the molecular structure. Seven different oxidized metabolites were found, both in the free and glucuronide conjugate forms. The major metabolite was the monohydroxyl-derivative PEN-OH (median molar fraction approximately 0.92 as a sum of free and glucuronide conjugated form). The product of further oxidation was the carboxyl-derivate PEN-COOH (median molar fraction approximately 0.03). After hydrolysis with β-glucuronidase, the free compounds were quantified in the presence of deuterated PEN as an internal standard; PEN-OH levels ranged from 230 to 460 μg/L, and PEN-COOH levels ranged from 5.2 to 16.7 μg/L. We propose a pathway for PEN metabolism in humans and suggest PEN-OH, after hydrolysis of glucuronide conjugates, as a biomarker for monitoring human exposure to PEN.

A preparative small-molecule mimic of liver CYP450 enzymes in the aliphatic C–H oxidation of carbocyclic N -heterocycles

“…5 A ). Penconazole 69 , a widely used fungicide, has monohydroxylated metabolites at C1 and C2 carbons of the propyl side chain ( 63 ). Electrochemical oxidation of penconazole 69 on an 85.2 mg scale (0.3 mmol) was reported to afford 17 mg C2 ketone 70 (19%) and 6.3 mg C3 ketone (7%) ( 38 ).…”

N-Ammonium Ylide Mediators for Electrochemical C–H Oxidation

“…Figure depicts specific applications of the ylide platform for the preparation of valuable metabolites and derivatives thereof. For instance, Penconazole 45 (Figure A) is a widely used fungicide with a primary metabolite profile in humans stemming from enzymatic oxidation on the propyl chain . When this compound was subjected to ylide-mediated electrochemical C–H oxidation ( Y4 ), the propyl group was successfully oxidized to afford the ketone products 46 in 26% yield in a 2:1 ratio (the alcohol corresponding to 46a being the natural metabolite).…”

Hair as a matrix to evaluate cumulative and aggregate exposure to pesticides in winegrowers

“…In fact, human metabolites of pesticides are often unknown, as biotransformation studies, carried out in the frame of the pesticide authorization process, are typically performed by oral dosage of pesticides in experimental animals. We recently showed that the main metabolite of the fungicide penconazole in human, dermally exposed in agriculture, is the hydroxyl derivative PEN-OH (4-(2,4-Dichloro-phenyl)-5-[1,2,4]triazol-1-yl-pentan-2-ol) (Mercadante et al, 2016); this is different from the carboxylic acid derivative PEN-COOH (4-(2,4-Dichloro-phenyl)-5-[1,2,4]triazol-1-yl-pentanoic acid) previously identified in experiments performed in rodents and goats (WHO/FAO, 2016). Besides, the discovery of metabolites relevant for humans and their measurement for biomonitoring purposes requires analytical assay development, including the availability of pure compounds for the quantitative determination.…”