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PubMedDate not supplied

Bitter gourd (Momordica charantia) extract activates peroxisome proliferator-activated receptors and upregulates the expression of the acyl CoA oxidase gene in H4IIEC3 hepatoma cells.

Peroxisome proliferator-activated receptor alpha (PPARalpha) is a ligand-dependent transcription factor that regulates the expression of genes involved in lipid metabolism and transport. Ligands/activators of PPARalpha, like fibrate-type drugs, may have hypolipidemic effects. To identify food that contains activators of PPARalpha, a transactivation assay employing a clone of CHO-K1 cells stably transfected with a (UAS)(4)-tk-alkaline phosphatase reporter and a chimeric receptor of Gal4-rPPARalpha LBD was used to screen ethyl acetate (EA) extracts of a large variety of food materials. It was found that the EA extract of bitter gourd (Momordica charantia), a common oriental vegetable, activated PPARalpha to an extent that was equivalent to or even higher than 10 microM Wy-14643, a known ligand of PPARalpha. This extract also activated PPARgamma to a significant extent which was comparable to 0.5 microM BRL-49653. The activity toward PPARalpha was mainly in the soluble fraction of the organic solvent. The EA extract prepared from the whole fruit showed significantly higher activity than that from seeds or flesh alone. The bitter gourd EA extract was then incorporated into the medium for treatment of a peroxisome proliferator-responsive murine hepatoma cell line, H4IIEC3, for 72 h. Treated cells showed significantly higher activity of acyl CoA oxidase and higher expressions of mRNA of this enzyme and fatty acid-binding protein, indicating that the bitter gourd EA extract was able to act on a natural PPARalpha signaling pathway in this cell line. It is thus worth further investigating the PPAR-associated health benefits of bitter gourd.

Acyl-CoA Oxidase↗
PubMed2006

Bitterness suppression of BCAA solutions by L-ornithine.

The purpose of the present study was to evaluate the bitterness-suppressing effect of L-ornithine (L-Orn) on single or mixed solutions of branched-chain amino acids (BCAAs) using human gustatory sensation tests and an artificial taste sensor. The BCAAs tested (L-isoleucine (L-Ile), L-leucine (L-Leu), and L-valine (L-Val)) are the main components of various enteral nutrients or supplements. The bitterness-suppression effect of L-Orn was also compared with the effect of L-Arg. L-Orn was effective in suppressing the bitterness of single or mixed solutions of BCAAs in human gustatory sensation tests, the effect being similar to or greater than that of L-Arg. The artificial taste sensor was able to predict the bitterness-suppressing effects of L-Orn and L-Arg. The response electric potential patterns of L-Val, L-Leu and L-Ile solutions to which 100 mM L-Arg had been added were quite similar to the sensor response patterns of the 100 mM L-Arg solutions alone. The relative response electric potential patterns of L-Val, L-Leu or L-Ile solutions containing 100 mM L-Orn in channels 5-8 (positively charged) are similar to that of single solution of 100 mM L-Orn.

Amino Acids, Branched-Chain↗
PubMed1999

Amino acid sequence analysis of bitter peptides from a soybean proglycinin subunit synthesized in Escherichia coli.

The cDNA encoding A1aB1b proglycinin was expressed in E. coli, for the efficient isolation of a single peptide responsible for the bitterness. The 55-kD proglycinin was highly purified, hydrolyzed, and further purified through a series of chromatographic steps to yield fractions with the major bitter peptides. The most bitter-tasting fractions contained peptides with average molecular weights lower than 1,700 Da. An analysis of the amino acid sequences indicated that many small bitter peptides (< 1,000 Da) are composed of uncharged polar amino acids as well as hydrophobic amino acids, with a charged residue often being present at either end. This suggests the involvement of a certain structural requirement in taste perception.

Amino Acid Sequence↗
PubMed2004

Possible association of acute lateral-wall myocardial infarction and bitter orange supplement.

OBJECTIVE: To report a possible incidence of acute lateral-wall myocardial infarction (MI) coinciding with the use of a Citrus aurantium L. (bitter orange)-containing dietary supplement in a patient with undetected coronary vascular disease. CASE SUMMARY: A 55-year-old white woman presented to the emergency department with symptoms of dull aching shoulder and chest pain. A review of medications during cardiac rehabilitation revealed the patient had ingested a multicomponent dietary supplement for weight loss containing 300 mg of bitter orange (Edita's Skinny Pill) for the past year. Although the patient's past medical history did not include hypertension, coronary disease, or hyperlipidemia, an arteriogram revealed a lesion in the left main coronary artery. She did have a smoking history. She was diagnosed with acute lateral-wall MI and hospitalized for 4 days. DISCUSSION: Consumers generally consider dietary supplements safe. However, some supplements taken for weight loss contain ingredients that have been associated with cardiovascular events. Although consumers are becoming more aware of the serious adverse effects secondary to products containing ingredients such as Ma huang and ephedra, reports involving other ingredients are increasing. Bitter orange or synephrine, found in bitter orange, has been associated with adverse cardiovascular reactions. Based on the Naranjo probability scale, C. aurantium is possibly associated with this cardiovascular event. CONCLUSIONS: The use of C. aurantium-containing supplements may present as a risk for cardiovascular toxicity; however, additional studies/case reports are needed to validate this conclusion.

Anti-Obesity Agents↗
PubMed2004

Bitter taste receptors for saccharin and acesulfame K.

Weight-conscious subjects and diabetics use the sulfonyl amide sweeteners saccharin and acesulfame K to reduce their calorie and sugar intake. However, the intrinsic bitter aftertaste, which is caused by unknown mechanisms, limits the use of these sweeteners. Here, we show by functional expression experiments in human embryonic kidney cells that saccharin and acesulfame K activate two members of the human TAS2R family (hTAS2R43 and hTAS2R44) at concentrations known to stimulate bitter taste. These receptors are expressed in tongue taste papillae. Moreover, the sweet inhibitor lactisole did not block the responses of cells transfected with TAS2R43 and TAS2R44, whereas it did block the response of cells expressing the sweet taste receptor heteromer hTAS1R2-hTAS1R3. The two receptors were also activated by nanomolar concentrations of aristolochic acid, a purely bitter-tasting compound. Thus, hTAS2R43 and hTAS2R44 function as cognate bitter taste receptors and do not contribute to the sweet taste of saccharin and acesulfame K. Consistent with the in vitro data, cross-adaptation studies in human subjects also support the existence of common receptors for both sulfonyl amide sweeteners.

Aristolochic Acids↗
PubMed2005

Absence of QTc-interval-prolonging or hemodynamic effects of a single dose of bitter-orange extract in healthy subjects.

STUDY OBJECTIVE: To evaluate the hemodynamic and electrocardiographic effects of a single dose of commercially available bitter-orange dried-fruit extract, which is increasingly being used in dietary supplements. DESIGN: Randomized, double-blind, placebo-controlled, crossover study. SETTING: University of Connecticut, Storrs Campus. SUBJECTS: Eighteen healthy volunteers aged 18 years or older. INTERVENTION: Subjects were given either placebo or bitter-orange dried-fruit extract (450 mg standardized to 27 mg of m- or p-synephrine) in phase 1. The opposite treatment was given during phase 2 after a washout period of at least 7 days. MEASUREMENTS AND MAIN RESULTS: The rate-corrected QT (QTc) interval and blood pressure were measured before dosing and at 1, 3, 5, and 8 hours after dosing. Mean+/-SD values of the maximum postdose values were compared between groups. Subjects receiving bitter-orange extract versus those receiving placebo had similar postdose QTc intervals (402+/-29 vs 403+/-24 msec, p=0.653), systolic blood pressure (114+/-10 vs 115+/-8 mm Hg, p=0.686) and diastolic blood pressure (68+/-9 vs 68+/-8, p=0.879). CONCLUSION: Bitter-orange dried-fruit extract standardized to m- or p-synephrine 27 mg did not significantly alter the QTc interval or blood pressure after a single dose was administered. Future studies are necessary to ensure the safety of this herbal product with multiple doses.

Adult↗
PubMed1976

Mechanism of action of some bitter-tasting compounds on frog taste cells.

Effects of some bitter-tasting compounds on frog taste receptors were examined by recording glossopharyngeal nerve responses. The order of effectiveness of the compounds was quinine greater than brucine greater than formanilide greater than caffeine greater than urea. When the effects of quinine, brucine and caffeine on electrical responses in taste cells were examined, they all produced a depolarization associated with an increased input resistance. The action of the three compounds on taste receptors therefore, operates with a similar mechanism. The electrical responses in cells, produced by quinine, progressed slowly with time. Such effects with quinine are similar to those with procaine. After adaptation to quinine, the nerve responses to various chemical stimuli were gradually reduced in magnitude, while the electrical responses in taste cells during stimulation by chemicals became smaller. The mechanism of the effects of bitter stimuli are discussed in light of recent findings on the interaction of bitter stimuli with lipid monolayers and the extraction of lipid from bovine taste papillae by bitter stimuli.

Animals↗
PubMed1999

Bitter taste threshold and its relation to number of circumvallate papillae in the elderly.

The main purpose of this study was to determine the relationship between the number of circumvallate papillae and the bitter taste threshold with age. The study group consisted of 10 women (age range, 60-80) and 14 men (age range, 60-85) and the control group of 15 young women (age range, 18-25) and 15 young men (age range, 17-20); the total number of subjects was 54. The number of circumvallate papillae was counted by direct observation with the naked eye; bitter taste thresholds were evaluated by the three drop forced-choice method with an ascending series, using quinine sulfate dehydrate as the bitter agent. We observed that while the number of circumvallate papillae did not increase with age, the bitter taste threshold changed significantly with age.

Adolescent↗
PubMed1983

In vivo antitumor activity of the bitter melon (Momordica charantia).

The in vivo antitumor activity of a crude extract from the bitter melon (Momordica charantia) was determined. The extract inhibited tumor formation in CBA/H mice which had been given i.p. injections of 1.0 X 10(5) CBA/Dl tumor cells (77% of the untreated mice with tumors versus 33% of the treated mice with tumors after 6 weeks). The extract also inhibited tumor formation in DBA/2 mice which had been given i.p. injections of either 1 X 10(5) P388 tumor cells (0% of untreated mice survived after 30 days versus 40% survival of the treated mice) or 1 X 10(5) L1210 tumor cells (0% survival of untreated mice versus 100% of treated mice after 30 days). The in vivo antitumor effect required both the prior exposure of tumor cells to the extract (2 hr) in vitro and i.p., biweekly injections of the extract into the mice. The optimum dose for tumor inhibition (8 micrograms protein, biweekly, i.p.) was not toxic to mice for at least 45 days of treatment. This same treatment caused a marked enhancement of C3H mouse thymic cell response to concanavalin A in vitro. When compared to the untreated control mice, the bitter melon-injected animals exhibited a 4-fold-higher incorporation of tritiated thymidine into trichloroacetic acid-precipitable material after 48 hr of exposure to 50 micrograms of concanavalin A. Nylon wool-purified spleen cells from these same bitter melon-treated mice exhibited an enhanced mixed lymphocyte reaction when exposed to irradiated P388 stimulator cells (186% of the untreated control mice). These data indicate that in vivo enhancement of immune functions may contribute to the antitumor effects of the bitter melon extract.

Animals↗
PubMed1993

Influence of bitter gourd (Momordica charantia) on growth and blood constituents in albino rats.

Feeding of bitter gourd (Momordica charantia) at 0.02, 0.1 and 0.5% (dry weight) levels in a semi-synthetic diet for a period of 8 weeks did not have any adverse influence on the food intake, growth and organ weights of normal adult rats. The haematological parameters of these experimental rats were also normal. Serum cholesterol levels of the rats receiving 0.5% bitter gourd were significantly lower than those of the control rats. There was no hypoglycaemic effect of bitter gourd in these normoglycaemic rats.

Animals↗
PubMed2005

Worldwide haplotype diversity and coding sequence variation at human bitter taste receptor loci.

Bitter taste perception in humans is mediated by receptors encoded by 25 genes that together comprise the TAS2R (or T2R) gene family. The ability to identify the ligand(s) for each of these receptors is dependent on understanding allelic variation in TAS2R genes, which may have a significant effect on ligand recognition. To investigate the extent of coding variation among TAS2R alleles, we performed a comprehensive evaluation of sequence and haplotype variation in the human bitter taste receptor gene repertoire. We found that these genes exhibit substantial coding sequence diversity. In a worldwide population sample of 55 individuals, we found an average of 4.2 variant amino acid positions per gene. In aggregate, the 24 genes analyzed here, along with the phenylthiocarbamide (PTC) receptor gene analyzed previously, specify 151 different protein coding haplotypes. Analyses of the ratio of synonymous and nonsynonymous nucleotide substitutions using the Ka/Ks ratio revealed an excess of amino acid substitutions relative to most other genes examined to date (Ka/Ks = 0.94). In addition, comparisons with more than 1,500 other genes revealed that levels of diversity in the TAS2R genes were significantly greater than expected (pi = 0.11%; p < 0.01), as were levels of differentiation among continental populations (FST = 0.22; p < 0.05). These diversity patterns indicate that unusually high levels of allelic variation are found within TAS2R loci and that human populations differ appreciably with respect to TAS2R allele frequencies. Diversity in the TAS2R genes may be accounted for by natural selection, which may have favored alleles responsive to toxic, bitter compounds found in plants. These findings are consistent with the view that different alleles of the TAS2R genes encode receptors that recognize different ligands, and suggest that the haplotypes we have identified will be important in studies of receptor-ligand recognition.

Alleles↗
PubMed2001

Quantification of suppression of bitterness using an electronic tongue.

Phospholipids, such as phosphatidic acid, suppress bitter taste without affecting other taste qualities. In the present study, we detected and quantified this suppression effect with an electronic tongue whose transducer is composed of several kinds of lipid/polymer membranes with different characteristics. We measured a phospholipid cocktail and various kinds of taste substances with five basic taste qualities. The responses to quinine hydrochloride and L-tryptophan, which have a bitter taste, were reduced as the phospholipid concentration was increased, and the responses to the other taste substances were not affected by the phospholipids, as with the human sensation test. Furthermore, the change of bitter intensity caused by phospholipid was quantified by principal component analysis and the tau scale, which expresses the relationship between taste intensity and taste substance concentration. The results are compared with those of the human sensory test and discussed.

Computer Simulation↗
PubMedDate not supplied

Sweet and bitter taste: structure and conformations of two aspartame dipeptide analogues.

The synthesis and X-ray diffraction analysis of two dipeptide taste ligands have been carried out as part of our study of the molecular basis of taste. The compounds L-aspartyl-D-alpha-methylphenylalanine methyl ester [L-Asp-D-(alpha Me)Phe-OMe] and L-aspartyl-D-alanyl-2,2,5, 5-tetramethylcyclopentanyl ester [L-Asp-D-Ala-OTMCP] elicit bitter and sweet taste, respectively. The C-terminal residues of the two analogues adopt distinctly different conformations in the solid state. The aspartyl moiety assumes the same conformation found in other dipeptide taste ligands with the side-chain carboxylate and the amino groups forming a zwitterionic ring with a conformation defined by psi, chi 1 = 157.7 degrees, -61.5 degrees for L-Asp-D-Ala-OTMCP and 151.0 degrees, -68.8 degrees for L-Asp-D-(alpha Me)Phe-OMe. In the second residue, a left-handed helical conformation is observed for the (alpha Me)Phe residue of L-Asp-D-(alpha Me)Phe-OMe with phi 2 = 49.0 degrees and psi 2 = 47.9 degrees, while the Ala residue of L-Asp-D-Ala-OTMCP adopts a semi-extended conformation characterized by dihedral angles phi 2 = 62.8 degrees and psi 2 = -139.9 degrees. The solid-state structure of the bitter L-Asp-D-(alpha Me)Phe-OMe is extended: while the crystal structure of the sweet L-Asp-D-OTMCP roughly adopts the typical L-shaped structure shown by other sweeteners. The data of L-Asp-D-(alpha Me)Phe-OMe are compared with those of its diastereoisomer L-Asp-L-(alpha Me)Phe-OMe. Conformational analysis of the two taste ligands in solution by NMR and computer simulations agrees well with our model for sweet and bitter tastes.

Aspartame↗
PubMed1997

Crystallization and preliminary X-ray studies of two serine proteinase inhibitors, BGIA and BGIT, from the seeds of bitter gourd.

Two serine proteinase inhibitors from seeds of the bitter gourd, BGIA (bitter gourd inhibitor against acidic amino acid-specific proteinase of Streptomyces griseus) and BGIT (bitter gourd trypsin inhibitor), were crystallized for X-ray structure determination. Crystals of BGIA belong to the monoclinic space group C2 with cell dimensions of a = 54.0 A, b = 23.7 A, c = 47.9 A, and beta = 105.4 degrees, and diffracted X-ray up to 1.5 A resolution. Crystals of BGIT belong to the triclinic space group P1 with cell dimensions of a = 22.8 A, b = 23.5 A, c = 28.4 A, alpha = 93.1 degrees, beta = 99.6 degrees, and gamma = 101.0 degrees, giving X-ray diffraction of over 1.2 A resolution. Intensity data of BGIA and BGIT crystals were collected using synchrotron radiation up to 1.7 and 1.4 A, respectively.

Crystallization↗
PubMed1976

[Occurrence of bitter taste after roasting of proteins (author's transl)].

Proteins of animal and plant origin (e.g. casein, zein, soyprotein, gliadin), heated to 260 degrees C for 10 min, yield aqueous extracts of strong bitter taste. The thresholds (0.0005-0.008%) are in the range of the value for chininhydrochloride (0.001%) and are much lower than thresholds for enzymatic protein hydrolyzates. Polysaccharides, heated under identical conditions (e.g. cellulose, starch, agar, carrageene), don't yield bitter products. It is assumed, that proteins are important precursors for bitter compounds on roasting.

Caseins↗
PubMed1975

[Relations between structure and bitter taste of amino acids and peptides. I. Amino acids and related compounds].

About 60 amino acids, amino acid esters, N-acyl amino acids, amines, and other related compounds were tested for bitter taste. The recognition thresholds are in the range from 100 muMol/ml (L-2-amino butyric acid) to 0.8 muMol/ml (benzamide). Essential structural requirements for bitter compounds are a polar (electrophilic) group and a hydrophobic one, which must be arranged in a defined manner. The results are summarized in a model which shows the zones of contact between bitter compound and receptor.

Amino Acids↗
PubMed1975

[Bitter peptides of casein isolated by hydrolysis with alpha-chymotrypsin and trypsin (author's transl)].

Two bitter peptides, H-Phe-Tyr-Pro-Glu-Leu-Phe-OH (I) and H-Val-Glu-Val-Phe-Ala-Pro-Pro-Phe-OH (II) were isolated from casein, hydrolyzed by alpha-chymotrypsin. The hexapeptide is cleaved by thermolysine between Glu and Leu. The two fragments are bitter too. A bitter dodecapeptide (III) was obtained 20 min hydrolysis of casein with trypsin. On account of amino acid composition and N-terminus peptide III is probably identical with a peptide from a 12 hrs hydrolyzate, described in 1970 by Matoba. The peptides I and III have equal taste tresholds in the range of 0.08-0.10 muM/ml.

Caseins↗
PubMed2006

Sweet and bitter taste of ethanol in C57BL/6J and DBA2/J mouse strains.

Studies of inbred strains of rats and mice have suggested a positive association between strain variations in sweet taste and ethanol intake. However, strain associations by themselves are insufficient to support a functional link between taste and ethanol intake. We used conditioned taste aversion (CTA) to explore the sweet and bitter taste of ethanol and ability to detect sucrose, quinine and ethanol in C57BL/6J (B6) and DBA/2J (D2) mouse strains that are frequently used in alcohol research. The present study showed that C57BL/6J mice generalized taste aversions from sucrose and quinine solutions to 10% ethanol and, reciprocally, aversions to 10% ethanol generalized to each of these solutions presented separately. Only conditioned aversions to quinine generalized to ethanol in the DBA/2J strain but an aversion conditioned to ethanol did not generalize reciprocally to quinine. Thus, considering these two gustatory qualities, 10% ethanol tastes both sweet and bitter to B6 mice but only bitter to D2. Both strains were able to generalize taste aversions across different concentrations of the same compound. B6 were able to detect lower concentrations of quinine than D2 but both strains were able to detect sucrose and (in contrast to previous findings) ethanol at similar concentrations. The strain-dependent gustatory profiles for ethanol may make an important contribution to the understanding of the undoubtedly complex mechanisms influencing high ethanol preference of B6 and pronounced ethanol avoidance of D2 mice.

Animals↗