Amadori- and N-nitroso-Amadori compounds and their pyrolysis products. Chemical, analytical and biological aspects.

N-(1-Deoxy-D-fructos-1-yl)-L-amino acids (fructose amino acids), Amadori compounds, are formed by reaction of D-glucose and L-amino acids and Amadori rearrangement. They are detected in heat-processed natural products and various foodstuffs and are key products of the Maillard-Browning reaction. N-Nitroso-N-(1-deoxy-D-fructos-1-yl)-L-amino acids (N-NO-fructose amino acids), N-NO-Amadori compounds, are formed in high yields by reacting fructose amino acids with sodium nitrite in acidic aqueous solution. They constitute a new class of non-volatile, bis-beta-oxidized nitrosamine derivatives with unknown biological (mutagenic and/or carcinogenic) activity. N-NO-Fructose amino acids may be formed in nitrite-containing Maillard systems (e.g., cured-meat products, tobacco) or in the human stomach after ingestion of food containing fructose amino acids and nitrite in food or saliva. Thirteen fructose amino acids and 13 N-NO-fructose amino acids (-gly, -ala, -val, -leu, -ileu, -ser, -thr, -met, -asp, -pheala, -tyr, -his, -trp) were prepared and investigated by high-resolution 1H-nuclear magnetic resonance (NMR) and 13C-NMR spectroscopy. The percentage amounts of the sugar ring forms (beta-pyranose, beta-furanose, alpha-furanose and alpha-pyranose) of these compounds in D2O mutarotation equilibrium were determined by 13C-NMR spectroscopy, together with the amounts (%) of E/Z isomers in the case of N-NO-compounds. The nitrosation products of D-fru-L-tyr, D-fru-L-his and D-fru-L-trp were isolated and identified by spectroscopic methods (NMR, infra-red). The N-NO-fructose amino acids can be separated by reversed-phase, ion-pairing, high-performance liquid chromatography. In some case the E/Z isomers are separated.