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Isolation and Partial Characterization of Four Fluorophores Formed by Nonenzymatic Browning of Methylglyoxal and Glutamine‐derived Ammonia
Author(s) -
Niquet Celine,
Pilard Serge,
Mathiron David,
Tessier Frederic J.
Publication year - 2008
Publication title -
annals of the new york academy of sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.712
H-Index - 248
eISSN - 1749-6632
pISSN - 0077-8923
DOI - 10.1196/annals.1433.025
Subject(s) - methylglyoxal , chemistry , aqueous solution , mass spectrometry , chromatography , ammonia , electrospray ionization , maillard reaction , tandem mass spectrometry , browning , methylamine , fluorescence , nuclear chemistry , organic chemistry , biochemistry , physics , quantum mechanics , enzyme
An aqueous solution of L‐glutamine (50 mmol/L) and methylglyoxal (100 mmol/L) was incubated at 120°C for 3 h in a 200 mmol/L phosphate buffer (pH 7.4). Four major fluorophores were revealed on the HPLC chromatogram. The same four fluorophores were obtained from the heating of a mixture of ammonia and methylglyoxal. After purification and concentration, they were structurally characterized by electrospray ionization mass spectrometry (ESI‐MS) using the high resolution and tandem mass spectrometry capabilities of a quadrupole time‐of‐flight MS. The accurate mass measurement of their [M+H] + ions, the MS fragment patterns, and the presence of one to two nitrogen indicate the formation of fluorophores with molecular formulas of C 7 H 7 NO 3 , C 8 H 9 NO 3 , C 12 H 14 N 2 O 4 , and C 12 H 14 N 2 O 5 . These results show that, in an aqueous solution, free glutamine undergoes a rapid degradation, leading to the formation of ammonia which reacts with methylglyoxal to form fluorescent heterocyclic Maillard products.