Structural analysis and taste evaluation of γ-glutamyl peptides comprising sulfur-containing amino acids.

The structures, flavor-modifying effects, and CaSR activities of γ-glutamyl peptides comprising sulfur-containing amino acids were investigated. The chemical structures, including the linkage mode of the N-terminal glutamic acid, of γ-L-glutamyl-S-(2-propenyl)-L-cysteine (γ-L-glutamyl-S-allyl-L-cysteine) and its sulfoxide isolated from garlic were established by comparing their NMR spectra with those of authentic peptides prepared using chemical methods. Mass spectrometric analysis also enabled determination of the linkage modes in the glutamyl dipeptides by their characteristic fragmentation.

Stereo-Selective Preparation of Teneraic Acid, trans-(2S,6S)-Piperidine-2,6-dicarboxylic Acid, via Anodic Oxidation and Cobalt-Catalyzed Carbonylation.

Teneraic acid (piperidine-2,6-dicarboxylic acid) is a naturally occurring imino acid that comprises three stereoisomers due to its two asymmetric centers at C2 and C6. The configuration of natural teneraic acid is reported to correspond to trans-(2S,6S). However, a few studies are focused on the stereospecific synthesis of trans-(2S,6S)-teneraic acid.

Design, synthesis, and taste evaluation of a high-intensity umami-imparting oxazole-based compound.

Umami taste is imparted predominantly by monosodium glutamate (MSG) and 5'-ribonucleotides. Recently, several different classes of hydrophobic umami-imparting compounds, the structures of which are quite different from MSG, have been reported. To obtain a novel umami-imparting compound, N-cinnamoyl phenethylamine was chosen as the lead compound, and a rational structure-optimization study was conducted on the basis of the pharmacophore model of previously reported compounds.

Synthesis, Characterization, and Evaluation of Thiazolidine Derivatives of Cysteine for Suppressing Eumelanin Production.

In the pathway of melanin biosynthesis, cysteine (Cys) is utilized for the synthesis of pheomelanin. Accordingly, Cys is considered to suppress the formation of brown-black eumelanin. Although attempts have been made to utilize Cys and its derivatives as skin-whitening agents, their instability and odor hinders their application as a cosmetic agent.

Practical large-scale production of dihydrocapsiate, a nonpungent capsaicinoid-like substance.

Capsinoids represent a novel group of capsaicinoid-like substances found in a nonpungent cultivar, Capsicum annuum "CH-19 Sweet." They have capsaicinoid-like physiological and biological properties while lacking the harmful stimuli of capsaicinoids. A large-scale synthesis of dihydrocapsiate (DCT) is established in this work.

Synthesis and evaluation of L-cystathionine as a standard for amino acid analysis.

L-Cystathionine is a key nonprotein amino acid related to metabolic conditions. The quantitative determination of L-cystathionine in physiological fluids by amino acid analysis is important for clinical diagnosis; however, certified reference material for L-cystathionine with satisfactory purity, content, and quantity has been unavailable until recently. Consequently, a practical and simple method for the preparation of L-cystathionine was examined, which involves thioalkylation of N-tert-butoxycarbonyl-L-cysteine tert-butyl ester, derived from L-cystine, with (2S)-2-(tert-butoxycarbonyl)amino-4-iodobutanoic acid tert-butyl ester, derived from L-aspartic acid, to obtain L-cystathionine with protecting groups, followed by single-step deprotection under mild conditions.

Concise Synthesis of (2R,4R)-Monatin.

Monatin, 4-hydroxy-4-(3-indolylmethyl)-glutamic acid, is a naturally occurring sweet amino acid. The (2R,4R)-monatin isomer has been found to be the sweetest among its four stereoisomers. A concise and efficient synthesis of (2R,4R)-monatin was accomplished by the alkylation of (4R)-N-tert-butoxycarbonyl (tBoc)-4-tert-butyldimethylsilyoxy-D-pyroglutamic acid methyl ester with tert-butyl 3-(bromomethyl)-1H-indole-1-carboxylate to give (4R)-N-tBoc-4-tert-butyldimethylsilyloxy-4-(N-tBoc-3-indolylmethyl)-D-pyroglutamic acid methyl ester, i.

Structure-CaSR-Activity Relation of Kokumi γ-Glutamyl Peptides.

Modulation of the calcium sensing receptor (CaSR) is one of the physiological activities of γ-glutamyl peptides such as glutathione (γ-glutamylcysteinylglycine). γ-Glutamyl peptides also possess a flavoring effect, i.e.

Preparation and Characterization of Four Stereoisomers of Monatin.

Monatin is a naturally occurring, sweet amino acid comprising four stereoisomers due to its two asymmetric centers at C2 and C4. However, the characteristics of each stereoisomer have not yet been fully investigated. To obtain a sufficient amount of racemic monatin for optical resolution, a synthetic method was developed by modifying a possible biosynthetic pathway, i.

Involvement of the calcium-sensing receptor in human taste perception.

By human sensory analyses, we found that various extracellular calcium-sensing receptor (CaSR) agonists enhance sweet, salty, and umami tastes, although they have no taste themselves. These characteristics are known as "kokumi taste" and often appear in traditional Japanese cuisine. Although GSH is a typical kokumi taste substance (taste enhancer), its mode of action is poorly understood.

Serotonin derivatives, major safflower (Carthamus tinctorius L.) seed antioxidants, inhibit low-density lipoprotein (LDL) oxidation and atherosclerosis in apolipoprotein E-deficient mice.

The effects of defatted safflower seed extract and its phenolic constituents, serotonin derivatives, on atherosclerosis were studied. Ethanol-ethyl acetate extract of safflower seeds (SSE) inhibited low-density lipoprotein (LDL) oxidation induced in vitro by an azo-containing free-radical initiator V70 or copper ions. Two serotonin derivatives [N-(p-coumaroyl)serotonin, CS; N-feruloylserotonin, FS] and their glucosides were identified as the major phenolic constituents of the extract.

Conformation analysis of aspartame-based sweeteners by NMR spectroscopy, molecular dynamics simulations, and X-ray diffraction studies.

We report here the synthesis and the conformation analysis by 1H NMR spectroscopy and computer simulations of six potent sweet molecules, N-[3-(3-hydroxy-4-methoxyphenyl)-3-methylbutyl]-alpha-L-aspartyl-S-tert-butyl-L-cysteine 1-methylester (1; 70 000 times more potent than sucrose), N-[3-(3-hydroxy-4-methoxyphenyl)-3-methylbutyl]-alpha-L-aspartyl-beta-cyclohexyl-L-alanine 1-methylester (2; 50 000 times more potent than sucrose), N-[3-(3-hydroxy-4-methoxyphenyl)-3-methylbutyl]-alpha-L-aspartyl-4-cyan-L-phenylalanine 1-methylester (3; 2 000 times more potent than sucrose), N-[3,3-dimethylbutyl]-alpha-L-aspartyl-(1R,2S,4S)-1-methyl-2-hydroxy-4-phenylhexylamide (4; 5500 times more potent than sucrose), N-[3-(3-hydroxy-4-methoxyphenyl)propyl]-alpha-L-aspartyl-(1R,2S,4S)-1-methyl-2-hydroxy-4-phenylhexylamide (5; 15 000 times more potent than sucrose), and N-[3-(3-hydroxy-4-methoxyphenyl)-3-methylbutyl]-alpha-L-aspartyl-(1R,2S,4S)-1-methyl-2-hydroxy-4-phenylhexylamide (6; 15 000 times more potent than sucrose). The "L-shaped" structure, which we believe to be responsible for sweet taste, is accessible to all six molecules in solution. This structure is characterized by a zwitterionic ring formed by the AH- and B-containing moieties located along the +y axis and by the hydrophobic group X pointing into the +x axis.