De novo synthesis of amino acids during the maillard reaction: qTOF/ESI mass spectrometric evidence for the mechanism of Akabori transformation

Bis(alaninato)iron(II) complexes as molecular scaffolds for the generation of N,N-di-glycated alanine derivatives in the presence of glucose

Metal ions are known to influence the course of the Maillard reaction through formation of various complexes such as bis(amino acids), these complexes are known to undergo more facile reaction with sugars. Due to this enhanced reactivity, the possible formation of di-glycated amino acids in glucose/alanine model systems with and without FeCl₂ was investigated using isotope labelling technique in conjunction with ESI/qTOF/MS/MS. Forty-eight derivatives of bis[N,N'-di-glycated alanine] iron(II) complexes were tentatively identified. These complexes incorporated one iron atom, two [¹³C-3] atoms from alanine and up-to twenty-four carbon atoms from glucose [¹³C-U], were incorporated as triose (C3), tetrose (C4), pentose (C5) or hexose (C6) moieties. Furthermore, the dissociation of the above complexes released variously substituted N,N-di-glycated alanine derivatives incorporating one alanine [¹³C-3] atom and up to twelve carbon atoms from glucose [¹³C-U]. The MS/MS analysis of diglycated alanines indicated that they follow similar fragmentation pathways as Amadori product of alanine.

Sugar-Conjugated Bis(glycinato)copper(II) Complexes and Their Modulating Influence on the Maillard Reaction

Transition metal ions are known to play an important role in the Maillard reaction in catalyzing redox reactions. They can also form strong binary complexes with amino acids with increased reactivity toward smaller aldehydes. To take advantage of this enhanced reactivity and to demonstrate the ability of glucose to conjugate with glycine copper complexes, model systems containing (Gly)2Cu and glucose or their isotopically enriched counterparts were heated in aqueous solutions in the presence and absence of paraformaldehyde at 110 °C for 2 h and the residues were analyzed by electrospray ionization/quadrupole time-of-flight/mass spectrometry (ESI/qTOF/MS). Isotope-labeling studies have indicated the ability of (Gly)2Cu complexes to act as molecular scaffolds and undergo multiple reactions with glucose to generate various complexes of sugar conjugates. These relatively stable intermediates allowed for the slower release of aroma and browning precursors, such as Amadori products, during heating, as assessed by the extent of browning and total volatile release.