Identification and quantification of the N-acetylcysteine conjugate of allyl isothiocyanate in human urine after ingestion of mustard.

Allyl isothiocyanate (AITC) is a constituent of cruciferous vegetables. It occurs widely in the human diet as a natural ingredient or food additive. AITC possesses numerous biochemical and physiological activities. It is cytotoxic and tumorigenic at high doses and also is a modulator of enzymes involved in metabolism of xenobiotics, including carcinogens. It is plausible that the wide consumption of dietary AITC may have profound effects on human health. To facilitate investigations of the effects of dietary AITC in humans, a method of measuring its uptake is needed. In this study, a urinary marker was developed for quantifying AITC uptake in humans. Four adult volunteers were asked to eat a meal containing brown mustard as the source of AITC. The 48-h urine samples were collected from these individuals and analyzed by reverse phase high performance liquid chromatography. A major urinary metabolite was found, which was identified as N-acetyl-S-(N-allylthiocarbamoyl)-L-cysteine, the N-acetylcysteine conjugate of AITC, by comparing its retention time and UV, nuclear magnetic resonance, and mass spectra with those of the synthetic standard. After ingestion of mustard, the AITC conjugate was detected in urine collected from 0 to 12 h. No conjugate was found in urine samples collected after 12 h. The major portion of this metabolite was excreted within 8 h. The average total excretion of AITC conjugate was 5.4 +/- 1.7 (SD) mg after consumption of 10 g of mustard and 12.8 +/- 2.0 mg when 20 g of mustard was consumed. Thus, a dose-dependent excretion of this metabolite was demonstrated.(ABSTRACT TRUNCATED AT 250 WORDS)