- Formation of 4-hydroxy-2,5-dimethyl-3(2H)-furanone and 4-hydroxy-2(or 5)-ethyl-5(or 2)-methyl-3(2H)-furanone through maillard reaction based on pentose sugars
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The caramel-like smelling compounds 4-hydroxy-2,5-dimethyl-3(2H)-furanone (HDMF) and 4-hydroxy-2(or 5)-ethyl-5(or 2)-methyl-3(2H)-furanone (HEMF) were identified by GC-MS and GC-MS/MS in Maillard reaction systems based on pentoses. The reaction was performed in a phosphate buffer by heating xylose, ribose, or arabinose with glycine or L-alanine at 90 °C for 1 h. HEMF was detected in the system pentose/alanine. HDMF was formed in both pentose/glycine and pentose/ alanine systems as well as directly from pentoses. Experiments using 13C-labeled glycine and alanine suggest the incorporation of the Strecker degradation products formaldehyde and acetaldehyde into the pentose moiety, forming the furanones HDMF and HEMF, respectively. The presence of 12C-HDMF, which was approximately 30% of the total HDMF amount found in xylose/glycine, indicates that HDMF is partly formed by sugar fragmentation. The proposed mechanism for the formation of the furanones is based on decomposition of the Amadori compound via 2,3-enolization, chain elongation by the Strecker aldehydes, and reduction of the resulting acetylformoin-type intermediates to the target molecules.
- Blank, Imre,Fay, Laurent B.
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- Nicotinamide-dependent Ene reductases as alternative biocatalysts for the reduction of activated alkenes
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Four NAD(P)H-dependent non-flavin ene reductases have been investigated for their ability to reduce activated C=C bonds in an asymmetric fashion by using 20 structurally diverse substrates. In comparison with flavin-dependent Old Yellow Enzyme homologues, a higher degree of electronic activation was required, because the best activities were obtained with enals and nitroalkenes rather than enones and carboxylic esters. Although FaEO from Fragaria x ananassa (strawberry) and its homologue SlEO from Solanum lycopersicum (tomato) exhibited a narrow substrate spectrum, progesterone 5β-reductase (At5β-StR) from Arabidopsis thaliana (thale cress) and leukotriene B4 12-hydroxydehydrogenase (LTB4DH/PGR) from Rattus norvegicus (rat) appear to be promising candidates, in particular for the asymmetric bioreduction of open-chain enals, nitroalkenes and α,β-unsaturated γ-butyrolactones. Competing nitro reduction and non-enzymatic Weitz-Scheffer epoxidation were largely suppressed. Electronically activated alkenes have been stereoselectively reduced by using a single-enzyme-cofactor system employing nicotinamide-dependent non-flavin ene reductases. Copyright
- Durchschein, Katharina,Wallner, Silvia,MacHeroux, Peter,Schwab, Wilfried,Winkler, Thorsten,Kreis, Wolfgang,Faber, Kurt
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p. 4963 - 4968
(2013/01/14)
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- Functional characterization of enone oxidoreductases from strawberry and tomato fruit
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Fragaria x ananassa enone oxidoreductase (FaEO), earlier putatively assigned as quinone oxidoreductase, is a ripening-induced, negatively auxin-regulated enzyme that catalyzes the formation of 4-hydroxy-2,5-dimethyl- 3(2H)-furanone (HDMF), the key flavor compound in strawberry fruit by the reduction of the α,β-unsaturated bond of the highly reactive precursor 4-hydroxy-5-methyl-2-methylene-3(2H)-furanone (HMMF). Here we show that recombinant FaEO does not reduce the double bond of straight-chain 2-alkenals or 2-alkenones but rather hydrogenates previously unknown HMMF derivatives substituted at the methylene functional group. The furanones were prepared from 4-hydroxy-5-methyl-3(2H)-furanone with a number of aldehydes and a ketone. The kinetic data for the newly synthesized aroma-active substrates and products are similar to the values obtained for an enone oxidoreductase from Arabidopsis thaliana catalyzing the α,β-hydrogenation of 2-alkenals. HMMF, the substrate of FaEO that is formed during strawberry fruit ripening, was also detected in tomato and pineapple fruit by HPLC-ESI-MSn and became 13C-labeled when D-[6-13C]-glucose was applied to the fruits, which suggested that a similar HDMF biosynthetic pathway occurs in the different plant species. With a database search (http://ted.bti.cornell.edu/ and http://genet.imb.uq.edu.au/Pineapple/), we identified a tomato and pineapple expressed sequence tag that shows significant homology to FaEO. Solanum lycopersicon EO (SIEO) was cloned from cDNA, and the protein was expressed in Escherichia coli and purified. Biochemical studies confirmed the involvement of SIEO in the biosynthesis of HDMF in tomato fruit.
- Klein, Dorothee,Fink, Barbara,Arold, Beate,Eisenreich, Wolfgang,Schwab, Wilfried
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p. 6705 - 6711
(2008/09/17)
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- Potential of gas chromatography-orthogonal acceleration time-of-flight mass spectrometry (GC-oaTOFMS) in flavor research
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Gas chromatography-orthogonal acceleration time-of-flight mass spectrometry (GC-oaTOFMS) is an emerging technique offering a straightforward access to a resolving power up to 7000. This paper deals with the use of GC-oaTOFMS to identify the flavor components of a complex seafood flavor extract and to quantify furanones formed in model Maillard reactions. A seafood extract was selected as a representative example for complex food flavors and was previously analyzed using GC-quadrupole MS, leaving several molecules unidentified. GC-oaTOFMS analysis was focused on these unknowns to evaluate its potential in flavor research, particularly for determining exact masses, N-Methyldithiodimethylamine, 6-methyl-5-hepten-2-one, and tetrahydro-2,4-dimethyl-4H-pyrrolo- [2,1-d]-1,3,5-dithiazine were successfully identified on the basis of the precise mass determination of their molecular ions and their major fragments. A second set of experiments was performed to test the capabilities of the GC-oaTOFMS for quantification. Calibration curves were found to be linear over a dynamic range of 103 for the quantification of furanones. The quantitative data obtained using GC-oaTOFMS confirmed earlier results that the formation of 4-hydroxy-2,5-dimethyl-3(2H)-furanone was favored in the xylose/glycine model reaction and 2(or 5) -ethyl-4-hydroxy-5(or2)-methyl-3(2H)-furanone in the xylose/alanine model reaction. It was concluded that GC-oaTOFMS may become a powerful analytical tool for the flavor chemist for both identification and quantification purposes, the latter in particular when combined with stable isotope dilution assay.
- Fay, Laurent B.,Newton, Anthony,Simian, Herve,Robert, Fabien,Douce, David,Hancock, Peter,Green, Martin,Blank, Imre
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p. 2708 - 2713
(2007/10/03)
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- Chemical and Enzymatic Syntheses of 6-Deoxyhexoses. Conversion to 2,5-Dimethyl-4-hydroxy-2,3-dihydrofuran-3-one (Furaneol) and Analogues
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6-Deoxy-D-fructose 1-phosphate (6-deoxyF-1-P) forms when a solution containing D-fructose 1,6-diphosphate (FDP) and D-lactaldehyde is treated with the enzymes aldolase and triosephosphate isomerase (Scheme I).This transformation involves three reactions: aldolase-catalyzed cleavage of FDP to a mixture of dihydroxyacetone phosphate and D-glyceraldehyde phosphate, triosephosphate isomerase catalyzed equilibration of dihydroxyacetone phosphate and D-glyceraldehyde phosphate, and aldolase-catalyzed condensation of dihydroxyacetone phosphate and D-lactaldehyde to 6-deoxyF-1-P.An analogous process converts a mixture of FDP and L-lactaldehyde to 6-deoxysorbose 1-phosphate (6-deoxyS-1-P).Aldolase-catalyzed reaction of dihydroxyacetone phosphate, prepared separately, with D-lactaldehyde yields 6-deoxyF-1-P directly; similar reaction of dihydroxyacetone phosphate with α-hydroxybutyraldehyde yields a mixture of 6-methyl-6-deoxyhexose 1-phosphates.Acid-catalyzed hydrolysis of the sugar phosphates releases the corresponding free sugars.A mixture containing 6-deoxyhexoses is formed directly by base-catalyzed aldol condensation of dihydroxyacetone and D,L-lactaldehyde.Treatment of any of the 6-deoxyhexoses with acids generates 2,5-dimethyl-4-hydroxy-2,3-dihydrofuran-3-one (Furaneol, a flavor principle).Furaneol can also be prepared in moderate yields by hydrogenolysis of FDP and other hexose phosphates in alkaline media.
- Wong, Chi-Huey,Mazenod, Francois P.,Whitesides, George M.
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p. 3493 - 3497
(2007/10/02)
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- Process for making furanones
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This deals with a process for making furanones having the formula: STR1 wherein R represents a hydrogen atom or the methyl or ethyl group.
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