S-methylcysteine (SMC) is a minor amino acid naturally excreted in human urine, a protective agent against oxidative stress and a biotransformation product of the fumigant biocide methyl bromide and of nicotine. A metabolic source of SMC is catabolism of the repair catalytic protein MGMT (EC 22.214.171.124), which specifically removes the methyl group from the modified DNA nucleotide O-6-methyl-guanine to revert the normal GC base pairing. To assess the value of SMC and of S-methylmercapturic acid (SMMA) as candidate biomarkers of proliferative phenomena, a sensitive analytical method by GC-MS was applied in a pilot study of healthy subjects to assess their urinary elimination and the intra- and inter-individual variability. Extractive alkylation with butylchloroformate-n-butanol-pyridine (Husek technique) was employed for sample derivatization and isotope dilution GC-MS with S-[CD3]-SMC and -SMMA was applied for specific and sensitive detection. To resolve the target analytes from the main coeluting interferents in the derivatized urine extract a medium-polarity stationary phase was employed. SMMA was not detected in the morning urine of three healthy fertile-age women followed for one month above the minimum detectable level of approx. 500 µg/L while SMC concentrations were in the 0.02–0.7 µg/mL range (n = 61) with large inter-day and inter-individual variations. In a young healthy male urine samples taken throughout a few days yielded concentrations in the same 90–810 µg/L range (n = 11). These preliminary results points at SMC as a candidate biomarker for the study of methylation turnover in several biochemical processes.
Measurement of S-methylcysteine and S-methyl-mercapturic acid in human urine by alkyl-chloroformate extractive derivatization and isotope-dilution gas chromatography–mass spectrometry / F.M. Rubino, M. Pitton, D. Di Fabio, G. Meroni,E. Santaniello, E. Caneva, M. Pappini, A.L.P. Colombi. - In: BIOMEDICAL CHROMATOGRAPHY. - ISSN 0269-3879. - 25:3(2011), pp. 330-343.
|Titolo:||Measurement of S-methylcysteine and S-methyl-mercapturic acid in human urine by alkyl-chloroformate extractive derivatization and isotope-dilution gas chromatography–mass spectrometry|
RUBINO, FEDERICO MARIA (Primo)
PITTON, MARCO (Secondo)
PAPPINI, MARCO (Penultimo)
COLOMBI, ANTONIO LUCIANO PAOLO (Ultimo)
|Parole Chiave:||Husek derivatization; Isotope dilution; S-methyl-cysteine; S-methyl-mercapturic acid; Urine|
|Settore Scientifico Disciplinare:||Settore MED/44 - Medicina del Lavoro|
|Data di pubblicazione:||2011|
|Digital Object Identifier (DOI):||http://dx.doi.org/10.1002/bmc.1451|
|Appare nelle tipologie:||01 - Articolo su periodico|