Fd Chem. Toxic Vol 30, No 7, pp 575-583, 1992 0278-6915/92$5 00 + 0 00 Pnnted m Great Britain All rights reserved Copyright © 1992 PergamonPress Ltd METABOLISM OF AN IMIDAZOLE FUNGICIDE (PROCHLORAZ) IN THE RAT AFTER ORAL ADMINISTRATION L. LAIGNELET*:~, J.-L. RIVII~RE~ and J -C LHUGUENOT* *Ecole Nationale Sup6rleure de Blologie Apphqu~e fi la Nutrition et fi rAhmentatlon, Laboratolre de Blochlmle et Toxicologic Ahmentaires, Campus Unlversitaire Montrnuzard, 21000 DIjon and tEcole NaUonale V&rnnalre de Lyon, Laboratolre d'Ecotoxlcologle, BP 83, 69280 Marcy rEtode, France (Accepted 14 February 1992) Abstract--The metabohc fate and pathway of the lmldazolefungicideprochloraz {l-[N-propyl-N-2-(2,4,6- trlchlorophenoxy) ethyl carbamoyl] imldazole} were investigated in the rat after admlmstrataon of oral single doses with radlolabelled molecules. At both dose levels (50 and 250 mg/kg body weight), virtually all of the ingested [~4C-phenyl]prochlorazwas excreted m the urine or faeces within 96 hr, the bulk of excretion occurring between 24 and 48 hr after dosing Urinary elimination accounted for 61 and 68% of the respective mmal doses Unnary metabolic products were isolated and identified by thin-layer chromatography, gas chromatography or gas chromatography coupled with mass spectrometry analysis Prochloraz was completely metabohzed with no unchanged compound being excreted in the unne The main blotransformatlon products in rat urine were 2,4,6-tnchlorophenoxyacetlc acid and its corresponding alcohol, the latter as a glucuromc acid conjugate Ring hydroxylation also occurred, with the hydroxy- 2,4,6-trichlorophenoxyethanol and hydroxy-2,4,6-tnchlorophenoxyacetic acid metabohtes excreted in small amounts in the urine 2,4,6-Tnchlorophenol and uncon.lugated2,4,6-trtchlorophenoxyethanolwere identified as minor urinary metabohtes INTRODUCTION During the past decade the group of azole com- pounds have been developed as potent antifungal agents (Schwinn, 1983). Their mode of action in- volves inhibition of the cytochrome P-450-dependent 14c(-demethylase activity reqmred in the conversion of lanosterol to ergosterol (Henry and Sisler, 1984), an essentml steroid component of fungal cell mem- branes. The molecular basis of this inhibition is the presence of an ~m~dazole or tnazole moiety that interacts strongly with the iron atom of cytochrome P-450 (Rodngues et al., 1987; Vanden Bossche et al., 1984). The binding to the haem iron is fairly un- specific and inhibition of many other cytochrome P-450-dependent actwlties also occurs, including that of steroid metabohsm by various organs (Loose et al., 1983; Mason et al., 1985; Nagai et al., 1986; Sheets et al., 1986) as well as that of xenoblotic metabohsm (Meredith et al., 1985; Sheets and Mason, 1984). On the other hand, it has been shown that some lm~dazole-contaming fungicides are able to induce hepatic drug metabolism (Lavnjsen et al., 1986; Niemegeers et al., 1981; Tettenborn, 1970). Recently ~t has been demonstrated that one such fungicide, prochloraz {l-[N-propyl-N-2-(2,4,6-tri- chlorophenoxy) ethyl carbamoyl] imidazole} (Fig. 1), an lmidazole molecule widely used as an agricultural fungicide, is a potent inducer of the cytochrome :~To whom correspondence should be addressed. Abbremations: GC-MS = gas chromatography-mass spec- troscopy, TLC = thin-layer chromatography. P-450 and related monooxygenase activities m differ- ent species of animals (Lalgnelet et al, 1989; Rivl~re, 1983; Rwlrre et al., 1985). Despite its wxdespread agricultural use, there have been no published reports on the metabolic fate and pathway of prochloraz. A more detaded knowledge of the metabolism of prochloraz might allow a better understanding of its enzyme-reducing or -inhibiting properties and the toxicological implications of contaminatxon by this fungicide. This paper describes the ehmlnatlon pattern of prochloraz and the chromatographic isolation, identificaUon or quanUficahon of the metabolites of this fungicide that were found m rat urine MATERIALS AND METHODS Chemicals Unlabelled prochloraz (98% pure) was obtained from the Boots Company Ltd (Nottingham, UK). [14C]Prochloraz, umformly labelled in the phenyl ring (39.5mCi/g), was synthesized by Schermg Agro- chemicals Ltd (Cambridge, UK). Chemical and radiochemlcal purity was determined by HPLC and shown to be more than 98%. Figure 1 shows the chemical structure of prochloraz and the [~4C]- labelhng position. UnlabeUed reference compounds [2,4,6-tnchlorophenoxyacetic acid (100% pure) and 2,4,6-trichlorophenoxyethanol (100% pure)] were synthesized by Schering Agrochemicals Ltd. 2,4,6- Tnchlorophenol (100% pure) was supphed by Sigma Chemical Co. (La Verpilli+re, France). 575