title: Metabolism of methyleugenol in liver microsomes and primary hepatocytes: pattern of metabolites, cytotoxicity, and DNA-adduct formation.
abstract: Methyleugenol (1) is a constituent of many foods, in particular of herbal spices, and is used as flavoring agent in foodstuffs and as fragrance in cosmetics. 1 has been found to be carcinogenic in rodents, its metabolite, 1-hydroxymethyleugenol (2) acting as proximate DNA-binding carcinogen. We incubated 1 with liver microsomes of rat, bovine, and human origin. We found 2, 3-hydroxymethylisoeugenol (3), and 6-hydroxymethyleugenol (4) as major metabolites, and 1-oxomethyleugenol (5), 3-oxomethylisoeugenol (6), eugenol (9), chavibetol (11), and (RS)-2,3-dihydroxy-2,3-dihydromethyleugenol (7) as minor metabolites. Methyleugenol-2,3-epoxide (8), probably the precursor of 7, could not be detected. Incubations with synthetic metabolites were applied in order to uncover metabolic pathways. Incubations with primary rat hepatocytes revealed mainly nonconjugated 2 and conjugated 4, and minor amounts of partly conjugated 7 and conjugated 9 + 11. The "reactive metabolites" 3, 5, 6, and 8 were not detectable, possibly due to rapid reaction with cellular macromolecules. The highest cytotoxicity (resazurin reduction assay and lactate dehydrogenase leakage assay) was observed for the main metabolite 2 and its secondary metabolite 5 with EC(50) values of 50 and 10 µM, respectively. Deoxyadenosine or deoxyguanosine adducts were formed by incubating 1 or metabolites with rat hepatocytes. The rank order of adduct formation was 2 > 1 > 3 > 6, whereas 4, 5, and 8 were inactive. In conclusion, we present a virtually complete pattern of microsomal (rat, bovine, and human) and hepatocellular (rat) metabolites of 1 suggesting the formation of several reactive metabolites possibly involved in carcinogenicity, organ toxicity, and immune reactions.
authors.affiliation: Food Chemistry and Toxicology, University of Kaiserslautern, Erwin-Schroedinger-Strasse 52 , D-67663 Kaiserslautern, Germany.
authors.forename: Alexander T
authors.initials: AT
authors.lastname: Cartus
authors.forename: Kristin
authors.initials: K
authors.lastname: Herrmann
authors.forename: Lucas W
authors.initials: LW
authors.lastname: Weishaupt
authors.forename: Karl-Heinz
authors.initials: KH
authors.lastname: Merz
authors.forename: Wolfram
authors.initials: W
authors.lastname: Engst
authors.forename: Hansruedi
authors.initials: H
authors.lastname: Glatt
authors.forename: Dieter
authors.initials: D
authors.lastname: Schrenk
mesh_terms: D000818:Animals; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D018736:DNA Adducts; D005054:Eugenol / Q000031:analogs & derivatives* / Q000378:metabolism / Q000633:toxicity; D022781:Hepatocytes / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D008862:Microsomes, Liver / Q000187:drug effects* / Q000378:metabolism; D010084:Oxidation-Reduction; D051381:Rats; D053719:Tandem Mass Spectrometry
chemical_list: D018736:DNA Adducts; C005223:methyleugenol; D005054:Eugenol