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Thomas Hofmann - One of the best experts on this subject based on the ideXlab platform.
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quantitative studies taste reconstitution and omission experiments on the key taste compounds in morel mushrooms morchella deliciosa fr
Journal of Agricultural and Food Chemistry, 2006Co-Authors: Nina Rotzoll, And Andreas Dunkel, Thomas HofmannAbstract:Sensory-directed fractionation of an aqueous extract prepared from morel mushrooms led to the identification of gamma-aminobutyric Acid as the chemical inducer of the mouth-drying and mouth-coating oral sensation imparted by morels. Additionally, L-glutamic Acid, L-Aspartic Acid, succinic Acid, and the previously unknown (S)-malic Acid 1-O-beta-D-glucopyranoside, coined (S)-morelid, were detected as additional important umami-like taste compounds. To further bridge the gap between pure structural chemistry and human taste perception, 33 putative taste compounds were quantified in an aqueous morel extract and then rated for their taste contribution on the basis of dose-over-threshold factors. To confirm these quantitative results, an aqueous taste reconstitute was prepared by blending aqueous solutions of 16 amino Acids, 6 organic Acids, 3 purines, 4 carbohydrates, 3 minerals, and (S)-morelid in their "natural" concentrations. Triangle tests revealed that the taste profile of this biomimetic organoleptic cocktail did not differ significantly from the taste profile of authentic morel extract. To finally narrow down the number of key taste compounds, taste omission experiments were performed demonstrating that (S)-morelid together with L-glutamic Acid, L-Aspartic Acid, malic Acid, citric Acid, acetic Acid, and gamma-aminobutyric Acid are the key organoleptics of morel extract. Moreover, sensory experiments with model solutions showed that (S)-morelid not only imparts a sour and umami-like taste but is able to amplify the taste activity of monosodium glutamate, as well as sodium chloride, solutions.
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isolation structure determination synthesis and sensory activity of n phenylpropenoyl l amino Acids from cocoa theobroma cacao
Journal of Agricultural and Food Chemistry, 2005Co-Authors: Timo D. Stark, Thomas HofmannAbstract:Application of chromatographic separation and taste dilution analyses recently revealed besides procyanidins a series of N-phenylpropenoyl amino Acids as the key contributors to the astringent taste of nonfermented cocoa beans as well as roasted cocoa nibs. Because these amides have as yet not been reported as key taste compounds, this paper presents the isolation, structure determination, and sensory activity of these amino Acid amides. Besides the previously reported (−)-N-[3‘,4‘-dihydroxy-(E)-cinnamoyl]-3-hydroxy-l-tyrosine (clovamide), (−)-N-[4‘-hydroxy-(E)-cinnamoyl]-l-tyrosine (deoxyclovamide), and (−)-N-[3‘,4‘-dihydroxy-(E)-cinnamoyl]-l-tyrosine, seven additional amides, namely, (+)-N-[3‘,4‘-dihydroxy-(E)-cinnamoyl]-L-Aspartic Acid, (+)-N-[4‘-hydroxy-(E)-cinnamoyl]-L-Aspartic Acid, (−)-N-[3‘,4‘-dihydroxy-(E)-cinnamoyl]-l-glutamic Acid, (−)-N-[4‘-hydroxy-(E)-cinnamoyl]-l-glutamic Acid, (−)-N-[4‘-hydroxy-(E)-cinnamoyl]-3-hydroxy-l-tyrosine, (+)-N-[4‘-hydroxy-3‘-methoxy-(E)-cinnamoyl]-L-Aspartic Acid,...
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sensory guided decomposition of roasted cocoa nibs theobroma cacao and structure determination of taste active polyphenols
Journal of Agricultural and Food Chemistry, 2005Co-Authors: Timo D. Stark, Sabine Bareuther, Thomas HofmannAbstract:Sequential application of solvent extraction, gel permeation chromatography, and RP-HPLC in combination with taste dilution analyses, followed by LC-MS and 1D/2D-NMR experiments and thiolytic degradation, revealed that, besides theobromine and caffeine, the flavan-3-ols epicatechin, catechin, procyanidin B-2, procyanidin B-5, procyanidin C-1, [epicatechin-(4β→8)]3-epicatechin, and [epicatechin-(4β→8)]4-epicatechin were among the key compounds contributing to the bitter taste as well as the astringent mouthfeel imparted upon consumption of roasted cocoa. In addition, a series of quercetin, naringenin, luteolin, and apigenin glycopyranosides as well as a family of not previously identified amino Acid amides, namely, (+)-N-[4‘-hydroxy-(E)-cinnamoyl]-L-Aspartic Acid, (+)-N-[3‘,4‘-dihydroxy-(E)-cinnamoyl]-L-Aspartic Acid, (−)-N-[3‘,4‘-dihydroxy-(E)-cinnamoyl]-l-glutamic Acid, (−)-N-[4‘-hydroxy-(E)-cinnamoyl]-l-glutamic Acid, (−)-N-[4‘-hydroxy-(E)-cinnamoyl]-3-hydroxy-l-tyrosine, (+)-N-[4‘-hydroxy-3‘-methoxy-(E...
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isolation structure determination synthesis and sensory activity of n phenylpropenoyl l amino Acids from cocoa theobroma cacao
Journal of Agricultural and Food Chemistry, 2005Co-Authors: Timo D. Stark, Thomas HofmannAbstract:Application of chromatographic separation and taste dilution analyses recently revealed besides procyanidins a series of N-phenylpropenoyl amino Acids as the key contributors to the astringent taste of nonfermented cocoa beans as well as roasted cocoa nibs. Because these amides have as yet not been reported as key taste compounds, this paper presents the isolation, structure determination, and sensory activity of these amino Acid amides. Besides the previously reported (-)-N-[3',4'-dihydroxy-(E)-cinnamoyl]-3-hydroxy-L-tyrosine (clovamide), (-)-N-[4'-hydroxy-(E)-cinnamoyl]-L-tyrosine (deoxyclovamide), and (-)-N-[3',4'-dihydroxy-(E)-cinnamoyl]-L-tyrosine, seven additional amides, namely, (+)-N-[3',4'-dihydroxy-(E)-cinnamoyl]-L-Aspartic Acid, (+)-N-[4'-hydroxy-(E)-cinnamoyl]-L-Aspartic Acid, (-)-N-[3',4'-dihydroxy-(E)-cinnamoyl]-L-glutamic Acid, (-)-N-[4'-hydroxy-(E)-cinnamoyl]-L-glutamic Acid, (-)-N-[4'-hydroxy-(E)-cinnamoyl]-3-hydroxy-L-tyrosine, (+)-N-[4'-hydroxy-3'-methoxy-(E)-cinnamoyl]-L-Aspartic Acid, and (+)-N-[(E)-cinnamoyl]-L-Aspartic Acid, were identified for the first time in cocoa products by means of LC-MS/MS, 1D/2D-NMR, UV-vis, CD spectroscopy, and polarimetry, as well as independent enantiopure synthesis. Using the recently developed half-tongue test, human recognition thresholds for the astringent and mouth-drying oral sensation were determined to be between 26 and 220 micromol/L (water) depending on the amino Acid moiety. In addition, exposure to light rapidly converted these [E]-configured N-phenylpropenoyl amino Acids into the corresponding [Z]-isomers, thus indicating that analysis of these compounds in food and plant materials needs to be performed very carefully in the absence of light to prevent artifact formation.
Timo D. Stark - One of the best experts on this subject based on the ideXlab platform.
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isolation structure determination synthesis and sensory activity of n phenylpropenoyl l amino Acids from cocoa theobroma cacao
Journal of Agricultural and Food Chemistry, 2005Co-Authors: Timo D. Stark, Thomas HofmannAbstract:Application of chromatographic separation and taste dilution analyses recently revealed besides procyanidins a series of N-phenylpropenoyl amino Acids as the key contributors to the astringent taste of nonfermented cocoa beans as well as roasted cocoa nibs. Because these amides have as yet not been reported as key taste compounds, this paper presents the isolation, structure determination, and sensory activity of these amino Acid amides. Besides the previously reported (−)-N-[3‘,4‘-dihydroxy-(E)-cinnamoyl]-3-hydroxy-l-tyrosine (clovamide), (−)-N-[4‘-hydroxy-(E)-cinnamoyl]-l-tyrosine (deoxyclovamide), and (−)-N-[3‘,4‘-dihydroxy-(E)-cinnamoyl]-l-tyrosine, seven additional amides, namely, (+)-N-[3‘,4‘-dihydroxy-(E)-cinnamoyl]-L-Aspartic Acid, (+)-N-[4‘-hydroxy-(E)-cinnamoyl]-L-Aspartic Acid, (−)-N-[3‘,4‘-dihydroxy-(E)-cinnamoyl]-l-glutamic Acid, (−)-N-[4‘-hydroxy-(E)-cinnamoyl]-l-glutamic Acid, (−)-N-[4‘-hydroxy-(E)-cinnamoyl]-3-hydroxy-l-tyrosine, (+)-N-[4‘-hydroxy-3‘-methoxy-(E)-cinnamoyl]-L-Aspartic Acid,...
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sensory guided decomposition of roasted cocoa nibs theobroma cacao and structure determination of taste active polyphenols
Journal of Agricultural and Food Chemistry, 2005Co-Authors: Timo D. Stark, Sabine Bareuther, Thomas HofmannAbstract:Sequential application of solvent extraction, gel permeation chromatography, and RP-HPLC in combination with taste dilution analyses, followed by LC-MS and 1D/2D-NMR experiments and thiolytic degradation, revealed that, besides theobromine and caffeine, the flavan-3-ols epicatechin, catechin, procyanidin B-2, procyanidin B-5, procyanidin C-1, [epicatechin-(4β→8)]3-epicatechin, and [epicatechin-(4β→8)]4-epicatechin were among the key compounds contributing to the bitter taste as well as the astringent mouthfeel imparted upon consumption of roasted cocoa. In addition, a series of quercetin, naringenin, luteolin, and apigenin glycopyranosides as well as a family of not previously identified amino Acid amides, namely, (+)-N-[4‘-hydroxy-(E)-cinnamoyl]-L-Aspartic Acid, (+)-N-[3‘,4‘-dihydroxy-(E)-cinnamoyl]-L-Aspartic Acid, (−)-N-[3‘,4‘-dihydroxy-(E)-cinnamoyl]-l-glutamic Acid, (−)-N-[4‘-hydroxy-(E)-cinnamoyl]-l-glutamic Acid, (−)-N-[4‘-hydroxy-(E)-cinnamoyl]-3-hydroxy-l-tyrosine, (+)-N-[4‘-hydroxy-3‘-methoxy-(E...
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isolation structure determination synthesis and sensory activity of n phenylpropenoyl l amino Acids from cocoa theobroma cacao
Journal of Agricultural and Food Chemistry, 2005Co-Authors: Timo D. Stark, Thomas HofmannAbstract:Application of chromatographic separation and taste dilution analyses recently revealed besides procyanidins a series of N-phenylpropenoyl amino Acids as the key contributors to the astringent taste of nonfermented cocoa beans as well as roasted cocoa nibs. Because these amides have as yet not been reported as key taste compounds, this paper presents the isolation, structure determination, and sensory activity of these amino Acid amides. Besides the previously reported (-)-N-[3',4'-dihydroxy-(E)-cinnamoyl]-3-hydroxy-L-tyrosine (clovamide), (-)-N-[4'-hydroxy-(E)-cinnamoyl]-L-tyrosine (deoxyclovamide), and (-)-N-[3',4'-dihydroxy-(E)-cinnamoyl]-L-tyrosine, seven additional amides, namely, (+)-N-[3',4'-dihydroxy-(E)-cinnamoyl]-L-Aspartic Acid, (+)-N-[4'-hydroxy-(E)-cinnamoyl]-L-Aspartic Acid, (-)-N-[3',4'-dihydroxy-(E)-cinnamoyl]-L-glutamic Acid, (-)-N-[4'-hydroxy-(E)-cinnamoyl]-L-glutamic Acid, (-)-N-[4'-hydroxy-(E)-cinnamoyl]-3-hydroxy-L-tyrosine, (+)-N-[4'-hydroxy-3'-methoxy-(E)-cinnamoyl]-L-Aspartic Acid, and (+)-N-[(E)-cinnamoyl]-L-Aspartic Acid, were identified for the first time in cocoa products by means of LC-MS/MS, 1D/2D-NMR, UV-vis, CD spectroscopy, and polarimetry, as well as independent enantiopure synthesis. Using the recently developed half-tongue test, human recognition thresholds for the astringent and mouth-drying oral sensation were determined to be between 26 and 220 micromol/L (water) depending on the amino Acid moiety. In addition, exposure to light rapidly converted these [E]-configured N-phenylpropenoyl amino Acids into the corresponding [Z]-isomers, thus indicating that analysis of these compounds in food and plant materials needs to be performed very carefully in the absence of light to prevent artifact formation.
Ramesh Ramapanicker - One of the best experts on this subject based on the ideXlab platform.
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diastereoselective synthesis of d threo sphinganine l erythro sphinganine and spisulosine through asymmetric α hydroxylation of a higher homologue of garner s aldehyde
Tetrahedron, 2017Co-Authors: Vipin Kumar Jain, Ramesh RamapanickerAbstract:A diastereoselective route to the synthesis of D-threo-sphinganine, L-erythro-sphinganine and (−)-spisulosine from the higher homologue of Garner's aldehyde prepared from L-Aspartic Acid is reported. While the starting material contains one of the stereocenters in the target molecules, the other is generated by proline-catalyzed asymmetric α-hydroxylation of the aldehyde function. The two diastereomers of sphinganine are prepared from the same starting material and using the same sequence of reactions, but for the proline isomer used as the catalyst. The method described is simple and efficient and can easily be extended for the synthesis of other sphingoid bases.
Kibret Mequanint - One of the best experts on this subject based on the ideXlab platform.
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biomimetic l aspartic Acid derived functional poly ester amide s for vascular tissue engineering
Acta Biomaterialia, 2014Co-Authors: Darryl K Knight, Elizabeth R Gillies, Kibret MequanintAbstract:Abstract Functionalization of polymeric biomaterials permits the conjugation of cell signaling molecules capable of directing cell function. In this study, l -phenylalanine and l -aspartic Acid were used to synthesize poly(ester amide)s (PEAs) with pendant carboxylic Acid groups through an interfacial polycondensation approach. Human coronary artery smooth muscle cell (HCASMC) attachment, spreading and proliferation was observed on all PEA films. Vinculin expression at the cell periphery suggested that HCASMCs formed focal adhesions on the functional PEAs, while the absence of smooth muscle α-actin (SMαA) expression implied the cells adopted a proliferative phenotype. The PEAs were also electrospun to yield nanoscale three-dimensional (3-D) scaffolds with average fiber diameters ranging from 130 to 294 nm. Immunoblotting studies suggested a potential increase in SMαA and calponin expression from HCASMCs cultured on 3-D fibrous scaffolds when compared to 2-D films. X-ray photoelectron spectroscopy and immunofluorescence demonstrated the conjugation of transforming growth factor-β1 to the surface of the functional PEA through the pendant carboxylic Acid groups. Taken together, this study demonstrates that PEAs containing aspartic Acid are viable biomaterials for further investigation in vascular tissue engineering.
Hans-joachim Zeiss - One of the best experts on this subject based on the ideXlab platform.
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Recent advances in the stereoselective synthesis of L-phosphinothricin†‡
Pesticide Science, 1994Co-Authors: Hans-joachim ZeissAbstract:L-Phosphinothricin, the parent α-amino Acid of the herbicide glufosinate-ammonium, has been obtained in high enantiomeric purity by three different methods. The stereoselective alkylation of a D-valine-derived bis-lactim ether, followed by the hydrolysis of the heterocyclic intermediate, represents an attractive approach for gram-scale quantities in the laboratory. Another very efficient access to L-phosphinothricin consists of the asymmetric hydrogenation of a prochiral α-acylamido acrylate with a chiral bis-phosphine-rhodium catalyst, while the reaction of chiral pre-built C-4-fragments, like L-vinylglycine or L-2-amino-4-halobutyric Acid, which can be obtained from the inexpensive starting materials L-Aspartic Acid and L-glutamic Acid, with (methyl)phosphinic Acid derivatives represents a third route which allows the production of nearly enantiomerically pure L-phosphinothricin.
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A novel and convenient route to L-homoserine lactones and L-phosphinothricin from L-Aspartic Acid
Tetrahedron Letters, 1992Co-Authors: Michael G. Hoffmann, Hans-joachim ZeissAbstract:Abstract An efficient synthesis of L-phosphinothricin and N-protected-L-homoserine lactone derivatives starting from L-Aspartic Acid is described.
