Article
J. Agric. Food Chem., Vol. 57, No. 18, 2009 8597
presence of OPD lead to accumulation of all R-dicarbonyls,
which was helpful for isolation of quinoxalines. On the other
hand, this forbids statements on actual concentrations and on
reactivity of the participating structures. E.g. 3-deoxyglucosone
was the single major dicarbonyl in the absence of OPD, whereas
in the presence of OPD glucosone, 1-deoxyglucosone, Lederer’s
glucosone and 1-deoxythresosone were of much higher quanti-
tative importance. This means that highly reactive reductone
structures are degraded immediately after formation and espe-
cially once their direct precursor exhausts. At the same time more
stable structures as the 3-deoxy-isomers accumulate even in
absence of the trapping reagent due to lack of reactivity. This
might at least in part explain the difference of the low yields of free
R-dicarbonyls compared to the significant loss of lysine in the
reaction mixtures. OPD was also reported to impose major
oxidative stress on the particular research system (8). This lead
to glucosone artifact formation in incubations of the Amadori
product from glucose and lysine reacted at 37 °C due to the
presence of OPD. If this is also relevant to the reaction mixtures
studied herein, cannot be clarified by the conducted experiments.
In summary, we were able to present a thorough study for all
R-dicarbonyl structures relevant to the degradation of glucose in
presence of lysine using MLCCC as a successful technique to
isolate quinoxalines of dicarbonyl compounds. This novel use is
therefore highly suggestive of further applications for the polar
reaction products found within Maillard chemistry. Lederer’s
glucosone was confirmed to be an important intermediate com-
parable to 1-deoxyglucosone. In addition, 1-deoxypentosone was
unequivocally established as a novel R-dicarbonyl compound
arising from glucose via glucosone under oxidative conditions.
The complete reaction mechanisms are summarized by Figure 5.
To enhance clarity the formation of glyoxal and methylglyoxal
was excluded from the scheme and is discussed in depth above.
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ACKNOWLEDGMENT
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Received February 9, 2009. Revised manuscript received August 5, 2009.
Accepted August 8, 2009.