329769-49-5Relevant articles and documents
Systematic studies on structure and physiological activity of cyclic α-keto enamines, a novel class of cooling compounds
Ottinger,Soldo,Hofmann
, p. 5383 - 5390 (2001)
3-Methyl- and 5-methyl-2-(1-pyrrolidinyl)-2-cyclopenten-1-one were recently identified as intense cooling compounds in roasted dark malt. To gain more insights into the molecular requirements of these compounds for imparting a cooling sensation, 26 cyclic α-keto enamine derivatives were synthesized, and their physiological cooling activities were evaluated. Any modification of the amino moiety, the carbocyclic ring size, or incorporation of additional methyl groups led to a significant increase of the cooling threshold. Insertion of an oxygen atom into the 2-cyclopenten-l-one ring, however, increased the cooling activity, e.g., the cooling threshold of the 5-methyl-4-(1-pyrrolidinyl)3(2H)-furanone was found to be 16-fold below the threshold concentration determined for the 3-methyl-2-(1-pyrrolidinyl)-2-cyclopenten-1-one. Shifting the oxygen atom from the 4- into the 5-position of the cyclopentenone ring resulted in a even more drastic increase in cooling activity, e.g., the 4-methyl-3-(1-pyrrolidinyl)-2(5H)-furanone exhibited the strongest cooling effect at the low oral threshold concentration of 0.02-0.06 mmol/L, which is 35-fold below the value determined for (-)-menthol. In contrast to the minty smelling (-)-menthol, most of the α-keto enamines were found to be virtually odorless but impart a sensation of cooling to the oral cavity as well as to the skin, thus illustrating that there is no physiological link between cooling activity and mint-like odors.
On the influence of the carbohydrate moiety on chromophore formation during food-related Maillard reactions of pentoses, hexoses, and disaccharides
Frank, Oliver,Hofmann, Thomas
, p. 3246 - 3261 (2000)
The influence of the carbohydrate moiety on the formation of 2-[4-oxo-3-(pyrrolidin-1-yl)cyclopent-2-en1-ylidene]furan-3(2H)-one chromophores during food-related Maillard reactions from pentoses, hexoses, and disaccharides is reported. The orange compounds 1a,b and 2a,b detected in a roasted xylose/L-proline mixture, were identified as (2E)/(2Z)-4-hydroxy-5-methyl-2-[4-oxo-3-(pyrrolidin-1-yl)cyclopent-2-ene-1-yl idene]furan3(2H)-one and (2E)/(2Z)-5-methyl-2-[4-oxo-3-(pyrrolidin-1-yl)cyclopent-2-en-1-ylidene]-4-(p yrrolidin-1-yl)furan-3(2H)-one, respectively, by 1D- and 2D-NMR.LC/mass, and UV/VIS spectroscopy, as well as by synthetic experiments. Studies on their formation revealed that 1a, b and 2a, b are formed upon condensation of pentosederived 4-hydroxy-5-methyl- (3) and 5-methyl-4-(pyrrolidin-1-yl)furan-3(2H)-one (4), respectively, with 2hydroxycyclopenta-2,4-dien-1-one (5) and L-proline (Scheme 1). Further condensation reaction of 1a, b with furan-2-carbaldehyde yielded the red (2Z)-2-J|(5Z)-5-J[(2-furyl)methylidene]-4-oxo-3-(pyrrolidin-1-yl) cyclopent-2-en-1-ylidene|-4-hydroxy-5-methylfuran-3(2H)-one (6) as an additional novel Maillard chromophore. Replacement of the pentose by glucose in the mixture with L-proline led, after dry-heating, to the identification of the structurally related colored (2Z)/(2E)-2-[5-hydroxy-5-methyl-4-oxo-3-(pyrrolidin-1-yl)cyclopent-2-en-1ylid ene]-4-hydroxy-5-methylfuran-3(2H)-one (7a/7b) and to the characterization of 2,4,5-trihydroxy-5methylcyclopent-2-en-1-one (10) and 5-hydroxy-5-methylcyclopent-3-ene-1,2-dione (11) as key intermediates in chromophore formation from hexoses. Comparative studies on disaccharides revealed that not 7a/7b, but the colorless 4-(α-D-glucopyranosyloxy)-2-hydroxy-2-methyl-6H-pyran-3(2H)-one (8) and 2-(α-D-glucopyranosyloxy) -4.5-dihydroxy-5-methylcyclopent-2-en-1-one (9) were formed amongst the major degradation products of maltose (Scheme 4). The aglycons of 8 and 9 could not be liberated under food-related heating conditions, thus, inhibiting the formation of the color precursors 10 and 11 and, in consequence, of 7a/7b (Scheme 6). These data strongly suggest that the 1,4-glycosidic linkage of disaccharides is responsible for their lower efficiency in browning development compared to pentoses or hexoses.
