Measurement of S‐methylcysteine and S‐methyl‐mercapturic acid in human urine by alkyl‐chloroformate extractive derivatization and isotope‐dilution gas chromatography–mass spectrometry

• DOI: 10.1002/bmc.1451
• Publication Date: 2010-06-01T13:03:40Z
• Authors: Federico M Rubino; Marco Pitton; Daniela Di Fabio; Giuseppe Meroni; Enzo Santaniello; Enrico Caneva; Marco Pappini; Antonio Colombi
• Keywords: Isotope dilution

S-methylcysteine (SMC) is a minor amino acid naturally excreted in human urine, protective agent against oxidative stress and biotransformation product of the fumigant biocide methyl bromide nicotine. A metabolic source SMC catabolism repair catalytic protein MGMT (EC 2.1.1.37), which specifically removes group from modified DNA nucleotide O-6-methyl-guanine to revert normal GC base pairing. To assess value S-methylmercapturic (SMMA) as candidate biomarkers proliferative phenomena, sensitive analytical method by GC-MS was applied pilot study healthy subjects their urinary elimination intra- inter-individual variability. Extractive alkylation with butylchloroformate-n-butanol-pyridine (Husek technique) employed for sample derivatization isotope dilution S-[CD(3) ]-SMC -SMMA specific detection. resolve target analytes main coeluting interferents derivatized urine extract medium-polarity stationary phase employed. SMMA not detected morning three fertile-age women followed one month above minimum detectable level approx. 500 µg/L while concentrations were 0.02-0.7 µg/mL range (n = 61) large inter-day variations. In young male samples taken throughout few days yielded same 90-810 11). These preliminary results points at biomarker methylation turnover several biochemical processes.