Analysis of isothiocyanate mercapturic acids in urine: a biomarker for cruciferous vegetable intake.
Level 5 - mechanism / opinion, no new human data
Analytical bench validation study with proof-of-concept human data (n=2)
PubMed 12769523 · doi:10.1021/jf0341316
What was done
The authors developed and validated a solid phase extraction-high-performance liquid chromatography-electrospray ionization tandem mass spectrometry (SPE-HPLC-ESI-MS/MS) method to measure individual isothiocyanate mercapturic acids in urine. Assay performance was tested using urine samples fortified with three concentrations of isothiocyanate mercapturic acids (1.04, 10.5, and 313 microM), measured across six different days by three independent technicians. The method was also applied to 24 h urine collected from two volunteers after consuming broccoli and cauliflower.
What was found
The reliable analytical range was 1.0-310 microM in urine. Across the three fortified concentration levels (1.04, 10.5, and 313 microM), the repeatability relative standard deviation (RSD) was 12%, 6%, and 3%; the reproducibility RSD was 19%, 14%, and 8%; and spike recoveries were 103%, 104%, and 103%, respectively. In 24 h urine from the two volunteers, sulforaphane mercapturic acid (133 micromol) and allyl isothiocyanate mercapturic acid (4.7 micromol) were detected.
Why it matters
This paper validates a specific and reproducible mass spectrometry assay to quantify individual isothiocyanate mercapturic acids in urine, facilitating objective tracking of cruciferous vegetable intake in clinical and nutritional studies.
Limits
The human application was an uncontrolled proof-of-concept test in only two individuals. The abstract does not specify the exact amounts or preparation of the consumed vegetables, and the lower limit of quantification was 1.0 microM.
Cited by
- supports When ingested, sulforaphane is rapidly taken up by human cells, conjugated with glutathione, and excreted into urine.