Structure-taste relationships of L-aspartyl-aminomalonic acid diesters

Synthesis and sweetness characteristics of L-aspartyl-D-alanine fenchyl esters

Four isomers of the L-aspartyl-D-alanine fenchyl esters were prepared as potential peptide sweeteners. L-Aspartyl-D-alanine (+)-alpha-fenchyl ester and L-aspartyl-D-alanine (-)-beta-fenchyl ester showed sweetness with potencies 250 and 160 times higher than that of sucrose, respectively. In contrast, L-aspartyl-D-alanine (+)-beta-fenchyl ester and L-aspartyl-D-alanine (-)-alpha-fenchyl ester had the highest sweetness potencies at 5700 and 1100 times that of sucrose, respectively. In particular, L-aspartyl-D-alanine (-)-alpha-fenchyl ester had an excellent sweetness quality; but L-aspartyl-D-alanine (+)-beta-fenchyl ester did not have an excellent quality of sweetness because it displayed an aftertaste caused by the strong sweetness.

Sweeteners: state of knowledge review

Sweeteners are widely used in the food and pharmaceutical industry. The purpose of this paper is to review our current knowledge of sweet taste from chemical, biochemical, electrophysiological, psychophysical, and psychological points of view. The most common sweetners likely to be used in food and pharmaceuticals will be examined in detail. First, the chemical structures of sweet compounds including saccharides, diterpene glycosides, polyols, amino acids, dipeptides, and other nonsugars will be discussed. Second, biochemical approaches to understanding sweetner receptors will be reviewed. Third, electrophysiological and behavioral approaches to understanding sweetner receptors will be discussed. Fourth, psychophysical studies in humans will be shown to be consistent with biochemical and neurophysiological data. In addition, the basic mechanisms of sweet taste revealed by psychophysical studies will be given, including the role of multiple receptor sites, hydrogen bonding, and sodium transport. Finally, the factors that affect preference for sweet taste including the psychological and physiological variables associated with sweet preference will be explored.

A review of sweet taste potentiation brought about by divalent oxygen and sulfur incorporation

The plethora of high-potency sweetener research has allowed the construction of important structure-taste relationships. In light of new structure-taste relationships, it is instructive to review sweet taste potentiation brought about by divalent oxygen and sulfur incorporation. The taste of sulfur-containing organic compounds was reviewed in Japanese by Yasuo Ariyoshi in 1977. Several new representative examples of sweet taste potentiation and taste dichotomy (sweet and bitter) found within similar classes of oxygen- and sulfur-containing organic compound: amides, dipeptides, ureas, sulfamates, sulfonamides, oximes, sugars, dihydroisocoumarins, and others are reviewed. Special attention is given to the thioethers and thioureas in sulfamates, dipeptides, aryl ureas, and hybrid dipeptide ureas. The most notable contributions have arisen from the work of Nofre and Tinti at Université Claude Bernard in Lyons, France. A common trend emerges with certain sweeteners when a carbon atom is strategically replaced by sulfur or oxygen atoms. The net result is an increase in the sweetness two- to tenfold. With saccharins, the usual bitter, metallic taste is removed. Sweet taste receptor models that have been published are mainly based on the original Shallenberger and Acree model of the glucophores AH-B with contributions from Kier (AH-B-X). AH is a proton donor group, B is a proton acceptor group, and X is some hydrophobic group. All of the models have overlooked the contributions of divalent sulfur (often in place of oxygen) in bringing about sweetness potentiation. There is no precedence for localizing the energy-minimized structures of sulfur-containing sweeteners in a binding mode that includes sulfur. These sulfur potentiation loci are analyzed and illustrated in a computer-generated sweetener model to show the specific region in which sulfur is being "recognized" as a potentiating feature.

Mechanisms of chemosensory transduction in taste cells

The application of new techniques to the study of taste cells has revealed much about both the basic physiology of these cells and also about the mechanisms of taste transduction. The taste cells are electrically excitable cells with a variety of voltage-dependent ion currents. These ionic currents have an important role in the transduction of salt taste in mammals and frogs. In mudpuppies different ion channels are involved in the transduction of acidic-sour stimuli. The role of ion currents in the transduction of sweet taste is less clear. Some proposed mechanisms suggest an important role for ion currents and others suggest that the transduction process may be a biochemical event involving cell surface receptors and intracellular second messengers, possibly cAMP. The transduction of bitter taste seems to be a biochemical event involving cell surface receptors and intracellular second messengers in the inositol trisphosphate pathway. Thus, one cannot talk about "the mechanism" of taste transduction. Different taste modalities are transduced by different mechanisms. A corollary to this is that taste cells are not a homogeneous population of cells. In order to provide animals with the ability to discriminate between different taste modalities the taste cells consist of distinct subpopulations of cells based on their primary taste modality. The primary taste modality in a given cell is determined by the receptors and transduction mechanism(s) expressed in that cell. Evidence suggests that modality-specific receptors are expressed in a segregated manner in distinct subpopulations of taste cells. Secondary responses observed in gustatory axons may arise due to a lack of absolute specificity in the transduction processes and nonspecific effects of low pH and high ionic strength and osmolarity on the taste cells. An interesting area for future work will be to elucidate the mechanism(s) by which basal cells become committed to a given taste modality and how the gustatory neurons influence this process of differentiation. The involvement of the gustatory neurons is critical as they must synapse with taste cells of the correct taste modality to preserve the integrity of the information transferred to the CNS. This process of synaptogenesis is presumably mediated by the expression of taste-modality-specific, cell surface antigens on the basolateral domain of a taste cell and receptors on the appropriate neurons, but much work will be necessary to elucidate this process.(ABSTRACT TRUNCATED AT 400 WORDS)

Cyclopropane amino acid ester dipeptide sweeteners

A series of esters of L-aspartyl-1-aminocyclopropane carboxylic acid has been prepared and their sweet tastes determined. The sweetest ester prepared was about 300 times sweeter than sucrose. An attempt to use basic conditions during preparation of the dipeptide allyl ester led to succinimide formation of the aspartyl peptide even though the beta-carboxyl group was protected by a t-butyl ester function. The X-ray structure of the propyl ester (1c) was determined and its conformation is discussed.