Determination of new biomarkers to monitor the dietary consumption of isothiocyanates.

Isothiocyanates (ITCs) found in cruciferous vegetables have been associated with a reduced cancer risk in humans. We determined serum albumin adducts of allyl isothiocyanate (AITC), benzylisothiocyanate (BITC), phenylethylisothiocyanate (PEITC) and sulforaphane (SFN) in 85 healthy men from a dietary, randomized, controlled trial. After enzymatic digestion of albumin we determined the adducts of the ITCs with lysine (Lys) using liquid chromatography-tandem mass spectrometry. At the beginning of the study (and after 4 weeks) 4.7% (2.4%), 48.2% (35.3%), 5.9% (10.6%), and 24.7% (23.5%) of the samples were found positive for AITC-Lys, BITC-Lys, PEITC-Lys and SFN-Lys, respectively. This method enables the quantification of ITC adducts in albumin from large, prospective studies on diet and cancer.