Reductive amination derivatization for the quantification of garlic components by isotope dilution analysis

In this work, we synthesized internal standards for four garlic organosulfur compounds (OSCs) by reductive amination with C-13, D-2-formaldehyde, and developed an isotope dilution analysis method to quantitate these organosulfur components in garlic samples. Internal standards were synthesized for internal absolute quantification of S-allylcysteine (SAC), S-allylcysteine sulfoxide (alliin), S-methylcysteine (SMC), and S-ethylcysteine (SEC). We used a multiple reaction monitoring (MRM) to detect C-13, D-2-formaldehyde-modified OSCs by ultrahigh-performance liquid phase chromatography coupled with tandem mass spectrometry (UHPLC MS/MS) and obtained MS spectra showing different ratios of C-13, D-2-formaldehyde-modified and H-2-formaldehyde-modified compounds. The resulting labeled and unlabeled OSCs were exhibited correlation coefficient (R-2) ranged from 0.9989 to 0.9994, respectively. The average recoveries for four OSCs at three concentration levels ranged from 89% to 105%. By C-13, D-2-formaldehyde and sodium cyanoborohydride, the reductive amination-based method can be utilized to generate novel internal standard for isotope dilution and to extend the quantitative application. (C) 2017 Elsevier Ltd. All rights reserved.