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PubMed2001

Cellular responses of NG108-15 and SK-N-MC lines to sweet and bitter tastants as measured by extracellular acidification rates.

The Cytosensor microphysiometer device (Molecular Devices, Sunnyvale, CA) is capable of detecting small changes in cellular metabolism in response to specific bioactive ligands by measuring the extracellular acidification rate (ECAR). By measuring the ECAR we were able to detect responses of tissue culture cell lines to a variety of sweet- and bitter-tasting compounds. We examined in detail the responses of the NG108-15 (mouse neuroblastoma x rat glioma hybrid) and SK-N-MC (human neuroepithelioma) cell lines. We determined that NG108-15 cells were consistently very responsive to several potent sweeteners and bitter compounds, such as sodium saccharin, guanidino- sweeteners, denatonium benzoate, quinine, and ranitidine. These compounds could evoke changes in cellular metabolism (measured as ECAR) that were rapid in onset, saturable with respect to ligand concentration, and sensitive to several inhibitors of G-protein-coupled receptor signaling pathways. In sharp contrast, the neuroepithelioma SK-N-MC did not respond to any of the sweet or bitter compounds. Rapid changes in ECAR were easily detectable in both cell lines with the calcium ionophore A23187. Bradykinin elicited changes in the ECAR only in the NG108-15 cell line, which is known to express the B2 receptor. The changes in ECAR of the NG108-15 cell line in response to sweet and bitter taste compounds suggest these cells may expresses a receptor(s) specific for small sapid molecules.

Acids↗
PubMed1989

Some properties of Streptococcus faecalis subsp. liquefaciens isolated from cheese with special reference to production of bitterness.

Streptococcus faecalis subsp. liquefaciens was examined for proteolysis and development of bitterness in sterile buffaloes' skim milk with and without some additives. Cell population and the pH of milk were the most important factors in the breakdown of casein and development of bitterness. Sodium chloride level, altering the final concentration of bacteria in milk, had a direct role in the production of bitter peptides. Calcium ions up to 5 mM did not affect proteolysis whereas higher concentrations were inhibitory. Electrophoretic analysis of proteose-peptone formed in sterile skim milk with and without NaCl revealed the presence of 3 peptides, 2 of which were probably associated with bitterness. S. faecalis subsp. liquefaciens produced acidity slowly, but was the most acid producer (1.25% after 72 h) of the streptococci. However, milk coagulated enzymatically and the curd shrinkage was related to salt-dependent acidity. Strains of the organism coagulated fresh citrated human plasma within 21 h at 30 degrees C, but without any visible fibrinolysis. The strains also were all alpha-haemolytic with occasionally a very few beta-haemolytic variants on sheep blood agar. On human blood agar, a weak alpha-reaction was given.

Animals↗
PubMed2005

Screening of bitterness-suppressing agents for quinine: the use of molecularly imprinted polymers.

The purpose of the present study was to examine the possibility of using molecularly imprinted polymers (MIPs) to screen for bitterness-suppressing agents. Quinine was selected as the bitter substance standard. L-arginine (L-Arg), L-ornithine (L-Orn), L-lysine (L-Lys), and L-citrulline (L-Ctr) were tested as bitterness suppressant candidates. In a high-performance liquid chromatography study using a uniformly sized MIP for cinchonidine, which has a very similar structure to quinine, the retention factor (k) of quinine was significantly shortened by the addition of L-Arg or L-Orn to the mobile phase, whereas slight or no decrease was observed when L-Ctr and L-Lys were added. The abilities of these amino acids to decrease the k of quinine were ranked in the following order: L-Arg = (L-Orn >(L-Ctr >>(L-Lys. A linear relationship between the reciprocal of k and the concentration of the amino acids indicated a single competitive model at a single site. The magnitude of the association constants obtained seemed to be directly related to the inhibitory effect of the test substances on the affinity of quinine for the receptor site. Nuclear magnetic resonance and molecular modeling studies suggested a one-to-two hydrogen-bonding-based complex formation of one quinine molecule with two methacrylic acid molecules (Q-2MAA) in chloroform. In the molecular modeling studies, the N--N distance of the quinine molecule in the assumed Q-2MAA complex was calculated to be 5.12 angstroms, similar to the N - N distances of the two amino acid complexes (L-Arg-2MAA, L-Orn-2MAA), which were 4.84 and 5.30 angstroms, respectively. This suggests that L-Arg and L-Orn may compete with the quinine molecule in the cinchonidine-imprinted space. Finally, the results of human gustatory sensation tests correlated well with the MIP data. The proposed method using MIPs seems to have a potential for screening bitterness-suppressing agents for quinine.

Arginine↗
PubMed1976

[Relations between structure and bitter taste of amino acids and peptides. II. Peptides and their derivatives (author's transl)].

About 80 peptides and their derivatives were tested for bitter taste. The taste thresholds are in the range of 70-80 muMol/ml (Gly-Val) to 0.01-0.02 muMol/ml (Bacitracin). They are dependent on nature and number of the side chains and on the hydrophobicity of the whole molecule. An estimation of the taste thresholds of all di-and tripeptides with known amino acid composition is possible on the basis of their hydrophobicity. As could be shown recently for bitter amino acids, a polar (electrophilic) and a hydrophobic group are essential requirements for bitter peptides also. This model corresponds to all sensory results, e.g. to the bitter taste of all hydrophobic peptides independent on their sequence and configuration and to the sweet taste of L-aspartyl dipeptide esters.

Amino Acids↗
PubMedDate not supplied

Effect of different proteases on bitterness of hemoglobin hydrolysates.

Hemoglobin was hydrolyzed by several enzymes (Proctase, Alcalase, Neutrase, papain). Hydrolysates were analyzed (degree of hydrolysis, gel permeation on Superose 12 column, tasting) and fractionated by ultrafiltration and 2-butanol extraction. The bitter peptides were isolated and identified. The results were compared with those already obtained with peptic hemoglobin hydrolysates. All the findings were confirmed. Ultrafiltration concentrated bitter compounds in the fraction corresponding to 500-5000 Da, and these compounds were selectively extracted by 2-butanol. All the bitter peptides belonged to the same fragment of the beta-chain of bovine hemoglobin. Finally, the use of a Superose 12 chromatographic column for easy detection of bitter hydrolysates without sensory analysis could be generalized for hemoglobin hydrolysates.

Amino Acid Sequence↗
PubMed2005

Association between 6-n-propylthiouracil (PROP) bitterness and colonic neoplasms.

Inadequate vegetable intake appears to increase colon cancer risk. Since genetic variation in taste influences vegetable preference, we tested associations between bitterness of 6-n-propylthiouracil (PROP), a measure of taste genetics, and number of colonic polyps, a measure of colon cancer risk, in 251 men who underwent screening lower endoscopy. Patients used the general Labeled Magnitude Scale to rate bitterness of 1.6 mg PROP delivered via filter paper. A subset of 86 patients reported weekly vegetable intakes, excluding salad or potatoes. PROP bitterness correlated significantly with polyp number, an effect separate from age-associated increases in polyp number. The PROP-polyp relationship was strongest in men over 66 years, and older men with polyps were most likely to be overweight or obese. In the subset reporting vegetable intake, men who tasted PROP as more bitter consumed fewer vegetables. These preliminary findings suggest that taste genetics may influence colon cancer risk, possibly through intake of vegetables.

Adult↗
PubMed1995

Bitter peptide from hemoglobin hydrolysate: isolation and characterization.

Two separation methods, ultrafiltration and 2-butanol extraction, have shown that a peptide is the major agent responsible for bitterness in peptic hemoglobin hydrolysates. It was easily purified from these complex mixtures by specific hydrophobic adsorption on Superose 12, a gel-filtration column, which could constitute an original and interesting method for bitterness detection. The bitter peptide which corresponded to VV-hemorphin 7, the fragment 32-40 of the beta chain of bovine hemoglobin, is first generated during proteolysis, then hydrolysed by pepsin. It exhibited a strong bitterness at 0.25 mM equivalent to 0.073 mM quinine sulfate or 21 mM caffeine.

Amino Acid Sequence↗
PubMed1985

Bitterness suppression as revealed by split-tongue taste stimulation in humans.

QHCl-sucrose and QHCl-NaCl mixtures administered to the anterior part of the human tongue led to substantial bitterness suppression as determined by the method of magnitude estimation. In the QHCl-sucrose condition components separated by the tongue's midline and those spatially mixed produced equal amounts of bitterness suppression. However, the QHCl-NaCl mixture produced significantly more bitterness suppression with the spatially mixed than with the spatially separated stimulus components. It is concluded that bitterness suppression in mixtures with sucrose occurs centrally and in mixtures with NaCl both peripherally and centrally.

Brain↗
PubMed1994

Generation of inositol phosphates in bitter taste transduction.

It is probable that there is a diversity of mechanisms involved in the transduction of bitter taste. One of these mechanisms uses the second messengers, inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG). Partial membrane preparations from circumvallate and foliate taste regions of mice tongues responded to the addition of known bitter taste stimuli by increasing the amount of inositol phosphates produced after 30 s incubation. Addition of both the bitter stimulus, sucrose octaacetate and the G-protein stimulant, GTP gamma S, led to an enhanced production of inositol phosphates compared with either alone. Pretreatment of the tissue samples with pertussis toxin eliminated all response to sucrose octaacetate plus GTP gamma S, whereas pretreatment with cholera toxin was without effect. Western blots of solubilized tissue from circumvallate and foliate regions probed with antibodies to the alpha-subunit of several types of G-proteins revealed bands reactive to antibodies against G alpha i1-2 and G alpha o, with no apparent activity to antibodies against G alpha i3. Given the results from the immunoblots and those of the toxin experiments, it is proposed that the transduction of the bitter taste of sucrose octaacetate in mice involves a receptor-mediated activation of a Gi-type protein which activates a phospholipase C to produce the two second messengers, IP3 and DAG.

Animals↗
PubMed1994

Use of Vernonia amygdalina by wild chimpanzee: possible roles of its bitter and related constituents.

Bitter principles and related constituents have been isolated from Vernonia amygdalina (Compositae), a plant ingested by wild chimpanzees sometimes suffering from parasite-related diseases in the Mahale Mountains National Park, Tanzania. These isolated constituents were the known sesquiterpene lactones (vernodalin, vernolide, hydroxyvernolide), and new stigmastane-type steroid glucosides (vernonioside A1-A4: for bitter tasting constituents and vernonioside B1-B3; for nonbitter related constituents). Antiparasitic activity tests of these constituents together with quantitative analyses of the major active constituents, vernodalin and vernonioside B1, supported the hypothesis that Mahale chimpanzees control parasite-related diseases by ingesting the pith of this plant, found to contain several steroid-related constituents. While the major active steroid-related constituents (vernonioside B1 and its primary aglycone, vernoniol B1) do not taste bitter themselves, it was hypothesized that the highly bitter constituents including vernodalin may play an important role as signals to the ingester guiding their choice of the appropriate plant, plant part, and possibly also as signals which help to control the amount of intake.

Animals↗
PubMed1994

Bitter taste in aging: compound-specific decline in sensitivity.

Threshold sensitivity to and the perceived intensity of two bitter compounds, quinine sulfate and urea, were assessed in 52 young adults and 60 elderly adults. Consistent with previous literature, age-related declines in sensitivity to the bitterness of quinine were observed at both threshold and suprathreshold levels. In contrast, the same young and elderly subjects showed comparable sensitivity to the bitterness of urea. These results provide further support for the existence of multiple bitter taste transduction sequences in humans, and indicate that they may be differentially affected by aging.

Adolescent↗
PubMed1990

Toxicological, nutritional and microbiological evaluation of tempe fermentation with Rhizopus oligosporus of bitter and sweet apricot seeds.

Bitter and sweet apricot seeds are by-products of the apricot processing industry. Bitter seeds, in particular, contain toxic levels of the cyanogenic substance amygdalin. Tempe was made from both kinds of seeds. The bitter seeds contain antimicrobial substances which must be removed by leaching and boiling prior to tempe fermentation. Apricot seed tempe had an agreeable taste. It contained approx. 21% (w/w) crude protein, 52% (w/w) crude fat, 1.5% (w/w) crude fibre and 25.5% (w/w) carbohydrates based on dry matter. The extent of biological acidification during soaking prior to fungal inoculation was inadequate to prevent growth of Bacillus cereus, and requires further optimisation. Bitter seeds were detoxified by the tempe process (approx. 70% of total cyanide was removed). However, additional improvement of the detoxification process is required to obtain a completely safe product.

Amygdalin↗
PubMed2004

The human taste receptor hTAS2R14 responds to a variety of different bitter compounds.

The recent advances in the functional expression of TAS2Rs in heterologous systems resulted in the identification of bitter tastants that specifically activate receptors of this family. All bitter taste receptors reported to date exhibit a pronounced selectivity for single substances or structurally related bitter compounds. In the present study we demonstrate the expression of the hTAS2R14 gene by RT-PCR analyses and in situ hybridisation in human circumvallate papillae. By functional expression in HEK-293T cells we show that hTAS2R14 displays a, so far, unique broad tuning towards a variety of structurally diverse bitter compounds, including the potent neurotoxins, (-)-alpha-thujone, the pharmacologically active component of absinthe, and picrotoxinin, a poisonous substance of fishberries. The observed activation of heterologously expressed hTAS2R14 by low concentrations of (-)-alpha-thujone and picrotoxinin suggests that the receptor is sufficiently sensitive to caution us against the ingestion of toxic amounts of these substances.

Bicyclic Monoterpenes↗
PubMed2006

Polyclonal antibodies mediated immobilization of a peroxidase from ammonium sulphate fractionated bitter gourd (Momordica charantia) proteins.

Polyclonal antibody bound Sepharose 4B support has been exploited for the immobilization of bitter gourd peroxidase directly from ammonium sulphate precipitated proteins. Immunoaffinity immobilized bitter gourd peroxidase exhibited high yield of immobilization. IgG-Sepharose 4B bound bitter gourd peroxidase showed a higher stability against heat, chaotropic agents (urea and guanidinium chloride), detergents (cetyl trimethyl ammonium bromide and Surf Excel), proteolytic enzyme (trypsin) and water-miscible organic solvents (propanol, THF and dioxane). The activity of immobilized bitter gourd peroxidase was significantly enhanced in the presence of cetyl trimethyl ammonium bromide and after treatment with trypsin as compared to soluble enzyme.

Ammonium Sulfate↗
PubMed2005

Partially purified bitter gourd (Momordica charantia) peroxidase catalyzed decolorization of textile and other industrially important dyes.

The aim of this study was to evaluate the enzymatic action of partially purified bitter gourd peroxidase for the degradation/decolorization of complex aromatic structures. Twenty-one dyes, with a wide spectrum of chemical groups, currently being used by the textile and other important industries have been selected for the study. Here, for the first time we have shown peroxidases from Momordica charantia (300 EU/gm of vegetable) to be highly effective in decolorizing industrially important dyes. Dye solutions, containing 50-200 mg dye/l, were used for the treatment with bitter gourd peroxidase (specific activity of 99.0 EU/mg protein). M. charantia peroxidases were able to decolorize most of the textile dyes by forming insoluble precipitate. When the textile dyes were treated with increasing concentration of enzyme, it was observed that greater fraction of the color was removed but four out of eight reactive dyes were recalcitrant to decolorization by bitter gourd peroxidase. Step-wise addition of enzyme to the decolorizing reaction mixture at the interval of 1h further enhanced the dye decolorization. The rate of decolorization was enhanced when the dyes were incubated with fixed quantity of enzyme for increasing times. Decolorization of non-textile dyes resulted in the degradation and removal of dyes from the solution without any precipitate formation. Decolorization rate was drastically increased when the textile and other industrially important non-textile dyes were treated with bitter gourd peroxidase in presence of 1.0 mM 1-hydroxybenzotriazole. Complex mixtures of dyes were prepared by taking three to four reactive textile and non-textile dyes in equal proportions. Each mixture was decolorized by more than 80% when treated with the enzyme in presence of 1.0 mM 1-hydroxybenzotriazole. Our data suggest that the peroxidase/mediator system is an effective biocatalyst for the treatment of effluents containing recalcitrant dyes from textile, dye manufacturing, dyeing and printing industries.

Color↗
PubMed2004

The effects of bitter melon (Momordica charantia) on serum and liver triglyceride levels in rats.

Effects of three different varieties (Koimidori, Powerful-Reishi, and Hyakunari) of bitter melon (Momordica charantia) and those of methanol fraction extract of Koimidori variety on serum and liver triglycerides were studied in rats. Feeding of diets containing either bitter melon or various fractions isolated by organic solvents caused no adverse effects on food intake or growth of rats. When the effect of three different varieties of bitter melon was compared, the Koimidori variety was found to be the most effective in lowering hepatic triglyceride levels as compared to the other two varieties, suggesting a variety-dependent difference in their activity. Furthermore, the active component(s) responsible for the liver triglyceride lowering activity of Koimidori variety was assumed to be concentrated in the methanol fraction, but not in other fractions such as the n-hexane, the acetone, or the residual fraction. The triglyceride lowering activity was furthermore confirmed by the dose-dependent reduction of hepatic triglyceride, resulting the lowest level in rats fed 3.0% supplementation. In these experiments, the effects on serum lipids were marginal. The results of the present and previous studies clearly show that bitter melon, especially Koimidori variety, exhibits a potent liver triglyceride-lowering activity.

Animals↗
PubMed2006

From Tonic-cups to Bitter-cups: Kwasi bita beker from Suriname Determination, past and present use of an ancient galenic artefact.

In the main markets of Paramaribo (Suriname), many stands offer what is locally called "Bitter-cups", or "Kwasi bita beker", small footed-cups, roughly carved from a whitish wood. The use of these cups is strictly medicinal and it seems to be restricted to Suriname, as they are not found in neighbouring countries (Guyana, French Guiana). The aim of this study was to identify the botanical origin of Bitter-cups still in use in the Saramaka traditional medicine (as information from field people was controversial), and document the ethnopharmacology of this original galenical artefact. Microscopic and high performance liquid chromatography (HPLC) analyses were carried out on Bitter-cup, and anatomical criteria (marginal parenchyma band, size of intervessel and vessel-ray pits, rays width and rays composition, vessels clustering, frequency and size of parenchyma pits) together with HPLC profiles of the macerates showed that the wood cup was similar to Quassia amara L. (Simaroubaceae) wood. Ethnopharmacological investigation indicates that the use of these cups is simply due to the pharmacological properties attributed to "bitters", and is strongly linked to tradition and cultural attitudes. This study also emphasizes the long lasting use of these cups, now restricted to Suriname only, with almost no variation over one century.

Chromatography, High Pressure Liquid↗
PubMed2004

Does bitter melon contain an activator of AMP-activated kinase?

Extracts of the unripe fruit of Momordica charantia--bitter melon, which flourishes throughout the tropics--appear to have utility in the management of type 2 diabetes. Rodent studies suggest that the thus-far-uncharacterized active components of such extracts enhance the efficiency of postprandial glucose storage in muscle and liver, and likely diminish excessive hepatic glucose output, while often down-regulating serum insulin--effects comparable to those reported for metformin. Other parallels between the actions of metformin and bitter melon in rodents appear to include: analogous effects on the hepatic activity of certain enzymes of glucose metabolism; increased expression of GLUT4 in the plasma membrane of skeletal muscle; a tendency to prevent weight gain; favorable effects on serum lipids; and an anti-promotional impact on cancer induction. Inasmuch as the clinical efficacy of metformin has recently been traced to its ability to activate AMP-activated kinase, it would be of interest to determine whether bitter melon extracts contain activators of this enzyme. The fact that bitter melon has the potential to down-regulate insulin suggests that, beyond its likely utility in the management of diabetes, it may have preventive value with respect to a wide range of disorders in which hyperinsulinemia plays a pathogenic role--and possibly could even favorably impact the aging process.

AMP-Activated Protein Kinases↗