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The effects of green tea on the metabolism of the food carcinogen 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) with emphasis on the formation of the detoxified glucuronides was studied. Two groups of 20 adult male and female Fischer 344 rats consumed 2% green tea or water for 6 weeks before being administered a single dose of 40 mg/kg body weight of [2-14C]IQ by oral gavage. Major metabolites in 24 h urine samples were separated by high-performance liquid chromatography (HPLC), including N-OH-IQ-N-glucuronide, 5-OH-IQ glucuronide and sulfate, IQ sulfamate and IQ itself. The structures of the main metabolites were established by mobility on the HPLC and by mass spectrometry. Sulfate esters and sulfamate were hydrolyzed by 0.1 N HCl for 15 min at 100°C, yielding 5-OH-IQ and high levels of IQ. HPLC of the resulting product showed the N-OH-IQ-N-glucuronide and the 5-OH-IQ glucuronide, as well as IQ. The male and female rats drinking tea displayed a significantly higher (P < 0.05) excretion of the two major glucuronides. We conclude that intake of green tea increases the excretion of N-OH-IQ-N-glucuronide, a detoxified metabolite of the proximate carcinogen N-OH-IQ.