The other six compounds are generated from the Maillard
reaction.[13] The tryptophan Amadori rearrangement product
(ARP)[14] is formed via Amadori rearrangement[15] at the
early stage of the Maillard reaction by the utilization of TRP.
5-(Hydroxymethyl)furfural (HMF) and 2,3-dihydro-3,5-dihydroxy-
6-methyl-4(H)-pyran-4-one (DDMP) are formed via the
3-deoxyglucosone and 1-deoxyglucosone dehydration pathway,
respectively.[16,17] 4-[2-Formyl-5-(hydroxymethyl)-1H-pyrrol-1-yl]
butanoic acid (PBA) is also a 3-deoxyglucosone degradation
product, formed from 4-aminobutyric acid and 3-deoxyglucosone
via nucleophilic intramolecular ring closure and keto–enol
tautomerism.[18] Acortatarin A and C were reported for the first
time in bread and as Maillard reaction products. It was proposed
that the formation of acortatarin A and C was from the reaction
between 3-deoxyglucosone and the related Strecker degradation
product 1,3-dideoxy-1-amino-fructose.[