DECREASE OF PLASMA AND URINARY OXIDATIVE METABOLITES OF ACETAMINOPHENAFTER CONSUMPTION OF WATERCRESS BY HUMAN VOLUNTEERS

To investigate the effect of the consumption of watercress (Nasturtium officinale R. Br.), a cruciferous vegetable, on acetaminophen metabol ism, the pharmacokinetics of acetaminophen and its metabolites were st udied in a crossover trial of human volunteers, A single oral dose of acetaminophen (1 gm) was given 10 hours after ingestion of watercress homogenates (50 gm). In comparison with acetaminophen only, the ingest ion of watercress resulted in a significant reduction in the area unde r the plasma cysteine acetaminophen (Cys-acetaminophen) concentration- time curve and in the peak plasma Cys-acetaminophen concentration by 2 8% +/- 3% and by 21% +/- 4% (mean +/- SE; n = 7; p < 0.005), respectiv ely. Correspondingly, the Cys-acetaminophen formation rate constant an d Cys-acetaminophen formation fraction were decreased by 55% +/- 9% an d 52% +/- 7% (p < 0.01), respectively. Consistent with the results obt ained from the plasma, the total urinary excretion of Cys-acetaminophe n in 24 hours was also reduced. A decrease of mercapturate acetaminoph en, a Cys-acetaminophen metabolite, was also shown in the plasma and u rine samples. However, the plasma pharmacokinetic processes and the ur inary excretions of acetaminophen, acetaminophen glucuronide, and acet aminophen sulfate were not altered significantly by the watercress tre atment. These results suggest that the consumption of watercress cause s a decrease in the levels of oxidative metabolites of acetaminophen, probably due to inhibition of oxidative metabolism of this drug.