Isolation and quantification in food of 6-(2-formyl-5-methylpyrrol-1-yl)-l-norleucine ("rhamnolysine") and its precursor 3,6-dideoxy-l-mannosone

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  • Michael Hellwig - , Dresden University of Technology (Author)
  • Thomas Henle - , Dresden University of Technology (Author)


In the Maillard reaction (non-enzymatic browning), reducing carbohydrates react to 1,2-dicarbonyl compounds that may combine with the epsilon-amino group of lysine to form characteristic pyrrole compounds such as pyrraline and formyline in a Paal-Knorr reaction. In the present study, the Maillard reaction of the rare sugar l-rhamnose was studied. The l-rhamnose-derived dehydration product 3,6-dideoxy-l-mannosone (3,6-DDM) was synthesized and structurally characterized via NMR. Mainly the -pyranose is formed in aqueous solution. 2-(2(S),3(S)-Dihydroxybutyl)quinoxaline was synthesized for the first time and used as a standard for quantification of 3,6-DDM in food. Analysis of 3,6-DDM after conversion to the respective quinoxaline via RP-HPLC-MS/MS revealed concentrations not exceeding 23 mu g/kg in food items such as coffee and brewing malt. Moreover, the Paal-Knorr reaction product of 3,6-DDM with lysine, namely 6-(2-formyl-5-methylpyrrol-1-yl)-l-norleucine (rhamnolysine) was synthesized for the first time by reaction of N--Boc-lysine and 3,6-DDM and purified by semi-preparative ion-exchange chromatography followed by characterization by NMR and HPLC-MS/MS. Rhamnolysine was analysed in 42 food items by RP-HPLC-MS/MS in the MRM mode after enzymatic hydrolysis. The highest concentration of the compound was found in rye bread crust (4.9mg/kg). It appears mainly in foods that are highly heat-treated, roasted or fried.


Original languageEnglish
Number of pages11
JournalEuropean Food Research and Technology
Issue number5
Publication statusPublished - May 2019
Externally publishedYes

External IDs

Scopus 85060566202
ORCID /0000-0001-8528-6893/work/142256500



  • Lysine, Maillard reaction, Glycation, Rhamnose, Advanced glycation end product (AGE), 3,6-Dideoxy-l-mannosone, Rare sugar, Rhamnolysine, MAILLARD REACTION-PRODUCTS, NUCLEAR-MAGNETIC-RESONANCE, L-RHAMNOSE, AQUEOUS-SOLUTION, 4-HYDROXY-2,5-DIMETHYL-3(2H)-FURANONE, DISACCHARIDES, SPECTRA, GLUCOSE, BEER