Rapid differentiation of D/L-homocysteine, D/L-homocystine, and S-allyl-D/L-cysteine using ion mobility-mass spectrometry

The development of a rapid analytical method for distinguishing chiral sulfur-containing compounds is essential due to the significant differences in biological activity exhibited by different enantiomers. This work presents a straightforward and rapid method for the chiral discrimination of D/L-homocysteine (D/L-Hcy), D/L-homocystine (D/L-Hcy 2 ), and S-allyl-D/L-cysteine (D/L-SAC) using cyclodextrin (CD) and metal adducts in conjunction with ion mobility-mass spectrometry (IM-MS). Through the formation of ternary complexes, separation was achieved with IM peak resolutions of 1.41 for [α-CD+D/L-Hcy+Co−H] + , 1.24 for [α-CD+D/L-Hcy 2 +Ca−H] + , and 1.65 for [β-CD+D/L-SAC+Fe−H] + . Theoretical calculations were performed to identify the optimal conformations of these ternary complexes. Conformational analysis elucidated distinct structural differences at the molecular level, providing insight into the chiral separation mechanism. Owing to its superior resolving power, this method enables the direct quantification of D/L enantiomers in mixtures. It was successfully applied to the determination of D/L-SAC in garlic samples, obviating the need for laborious sample pretreatment or derivatization steps. Overall, this work establishes a robust analytical platform for the chiral analysis of sulfur-containing amino acids and their derivatives. Graphical abstract