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, D-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, D-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, D-formaldehyde-modified and H-formaldehyde-modified compounds. The resulting labeled and unlabeled OSCs were exhibited correlation coefficient (R) 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, D-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.