Formulation and Evaluation of Taste Masked Oral Reconstitutable Suspension of Primaquine Phosphate

The purpose of this research was to mask the intensely bitter taste of primaquine phosphate (PRM) and to formulate suspension powder (cachets) of the taste masked drug. Taste masking was done using beta-cyclodextrin. To characterize and formulate taste masked cachets of PRM, the 1:25 M physical mixture was selected based on bitterness score. Phase solubility studies, fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and X-ray powder diffraction (XRPD) were performed to identify the physicochemical interaction between drug and carrier, hence its effect on dissolution. Cachets were evaluated for angle of repose, sedimentation characterization and pH. In vitro drug release studies for physical mixture and kneaded system were performed at pH, 1.2 and 6.8. Bitterness score was evaluated using gustatory sensation test. Phase solubility studies showed weak interaction between PRM and CD. The FTIR, DSC and XRPD studies indicated inclusion complexation in physical mixture and kneaded system. In addition, kneaded system and physical mixture exhibited better drug release at pH 1.2 and negligible effect at pH 6.8. Cachets prepared using physical mixture, (DS24), showed complete bitter taste masking and easy redispersibility. Taste evaluation of cachets in human volunteers rated tasteless with a score of 0 to DS24 and 3 to DS25. Thus, results conclusively demonstrated successful taste masking and formulation of cachets with taste masked drug.     

Development and Evaluation of Artemether Taste Masked Rapid Disintegrating Tablets with Improved Dissolution Using Solid Dispersion Technique

The purpose of this research was to mask the intensely bitter taste of artemether (ARM) and to formulate a rapid-disintegrating tablet (RDT) of the taste-masked drug. Taste masking was done by solid dispersion with mono amino glycyrrhyzinate pentahydrate (GLY) by solvent evaporation method. To characterize and formulate taste masked rapid disintegrating tablets (RDTs) of ARM, the 1:1M solid dispersion was selected based on bitterness score. Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and X-ray powder diffraction (XRPD) were performed to identify the physicochemical interaction between drug and carrier, hence its effect on dissolution. RDTs were evaluated for weight variation, disintegration time, hardness and friability. In vitro drug release studies were performed for RDTs at pH 1.2 and 6.8. Bitterness score was evaluated using mini-column method and compared with gustatory sensation test. FTIR spectroscopy and DSC showed no interaction while XRPD showed amorphization of ARM in GLY solid dispersion. RDTs prepared using solid dispersion, (RDT3), showed faster disintegration (within 28 s) and complete bitter taste masking of ARM. In addition, RDT3 exhibited better dissolution profile at both pH 1.2 and 6.8, than RDTs prepared from pure ARM (RDT5). Taste evaluation of RDTs in human volunteers rated tasteless with a score of 0 to RDT3 and 3 to RDT5. Mini-column revealed that RDT5 showed increase in number of persons who sensed bitterness with increased amount of ARM release while RDT3 sensed no bitterness. Thus, results conclusively demonstrated successful masking of taste and rapid disintegration of the formulated tablets in the oral cavity with improved dissolution.     

Individual differences in perception of bitterness from capsaicin, piperine and zingerone

It was recently shown that in some subjects capsaicin can evoke bitterness as well as burning and stinging, particularly in the circumvallate (CV) region of the tongue. Because perception of bitterness from capsaicin is characterized by large individual differences, the main goal of the present study was to learn whether people who taste capsaicin as bitter also report bitterness from structurally similar sensory irritants that are known to stimulate capsaicin-sensitive neurons. The irritancy and taste of capsaicin and two of its most commonly studied congeners, piperine and zingerone, were measured in individuals who had been screened for visibility of, and reliable access to, the CV papillae. Approximately half of these individuals reported tasting bitterness from all three irritants when the stimuli were swabbed directly onto the CV papillae. Concentrations that produced similar levels of burning sensation across subjects also produced similar (though lower) levels of bitter taste. These results are consistent with the hypothesis that capsaicin and its congeners stimulate bitterness via a common sensory receptor that is distributed differentially among individuals. Additionally, bitter tasters rated gustatory qualities (but not burning and stinging) slightly but significantly higher than did bitter non-tasters, which suggests that perception of capsaicin bitterness is associated with a higher overall taste responsiveness (but not chemesthetic responsiveness) in the CV region.     

An Electronic Tongue: Evaluation of the Masking Efficacy of Sweetening and/or Flavoring Agents on the Bitter Taste of Epinephrine

An epinephrine (E) tablet is under development for sublingual (SL) administration for the first-aid treatment of anaphylaxis; however, the inherent bitterness of E may hinder acceptability by patients, especially children. To assess the degree of E bitterness and to predict the masking effects of sweetening and/or flavoring non-medicinal ingredients (NMIs), the potential usefulness of an electronic tongue (e-Tongue) was evaluated. The e-Tongue sensors were conditioned, calibrated, and tested for taste discrimination. Six standard active pharmaceutical ingredients were used to build and validate a bitterness model which was then used to assess E bitartrate (EB) solutions from 0.3–9 mM. Taste-masking efficiency of aspartame (ASP), acesulfame potassium (ASK), and citric acid (CA) each at 0.5 mM was evaluated. Using EB 9 mM, the bitterness score was 20 on a scale of 20 (unacceptable) down to 1 (not detected). When NMIs 0.5 mM were added, neither ASK (17.2, unacceptable) nor was ASP (14.0, limit acceptable) effective in masking the bitter taste. When the combination of ASK and ASP was used, the bitterness score was reduced to 9.2 (acceptable). However, the addition of CA alone resulted in the best reduction of the bitterness score to 3.3 (not detected). Using the e-Tongue, the incorporation of a variety of sweetening and/or flavoring NMIs into a SL tablet of E could be shown to mask its bitter taste by up to 80%. These results should be confirmed by in vivo studies.     

Debittering of protein hydrolyzates

Enzymatic hydrolysis of proteins frequently results in bitter taste, which is due to the formation of low molecular weight peptides composed of mainly hydrophobic amino acids. Methods for debittering of protein hydrolyzates include selective separation such as treatment with activated carbon, extraction with alcohol, isoelectric precipitation, chromatography on silica gel, hydrophobic interaction chromatography, and masking of bitter taste. Bio-based methods include further hydrolysis of bitter peptides with enzymes such as aminopeptidase, alkaline/neutral protease and carboxypeptidase, condensation reactions of bitter peptides using protease, and use of Lactobacillus as a debittering starter adjunct. The causes for the production of bitter peptides in various food protein hydrolyzates and the development of methods for the prevention, reduction, and elimination of bitterness as well as masking of bitter taste in enzymatic protein hydrolyzates are presented.     

Studies on a Model of Bitter Peptides Including Arginine,Proline and Phenylalanine Residues. II. Bitterness Behavior of a Tetrapeptide (Arg-Pro-Phe-Phe) and Its Derivatives

In order to investigate the production of a strong bitter taste of the tetrapeptide, Arg-Pro-Phe-Phe (1), we synthesized 16 kinds of analogs and tasted them. From the results, it was clarified that all the constituent amino acid residues in Arg-Pro-Phe-Phe (1) were necessary for its strong bitter taste. For a further increase in bitterness potency, it was found that the bitterness production units necessary should be concentrated together. In addition, Arg-Pro-Gly-Gly (6) and Gly-Gly-Arg-Pro (7) were found to have no bitterness. This will be very useful not only for studies on debittering of food but also for basic studies on the taste production mechanism.     

Cross-adaptation and bitterness inhibition of L-tryptophan, L-phenylalanine and urea: further support for shared peripheral physiology

A previous study investigating individuals' bitterness sensitivities found a close association among three compounds: L-tryptophan (L-trp), L-phenylalanine (L-phe) and urea (Delwiche et al., 2001, Percept. Psychophys. 63, 761-776). In the present experiment, psychophysical cross-adaptation and bitterness inhibition experiments were performed on these three compounds to determine whether the bitterness could be differentially affected by either technique. If the two experimental approaches failed to differentiate L-trp, L-phe and urea's bitterness, then we may infer they share peripheral physiological mechanisms involved in bitter taste. All compounds were intensity matched in each of 13 subjects, so the judgments of adaptation or bitterness inhibition would be based on equal initial magnitudes and, therefore, directly comparable. In the first experiment, cross-adaptation of bitterness between the amino acids was high (>80%) and reciprocal. Urea and quinine-HCl (control) did not cross-adapt with the amino acids symmetrically. In a second experiment, the sodium salts, NaCl and Na gluconate, did not differentially inhibit the bitterness of L-trp, L-phe and urea, but the control compound, MgSO(4), was differentially affected. The bitter inhibition experiment supports the hypothesis that L-trp, L-phe and urea share peripheral bitter taste mechanisms, while the adaptation experiment revealed subtle differences between urea and the amino acids indicating that urea and the amino acids activate only partially overlapping bitter taste mechanisms.     

Reduction of saltiness and bitterness after a chlorhexidine rinse

Chronic rinsing with chlorhexidine, an oral-antiseptic, has been shown to decrease the saltiness of NaCl and the bitterness of quinine. The effect of acute chlorhexidine on taste has not been investigated. The purpose of the present study was to examine the effect of acute chlorhexidine rinses on taste intensity and quality of 11 stimuli representing sweet, salt, sour, bitter and savory. All stimuli were first matched for overall intensity so the effects of chlorhexidine would be directly comparable across compounds. As a control treatment, the bitter taste of chlorhexidine digluconate (0.12%) was matched in intensity to quinine HCl, which was found to cross-adapt the bitterness of chlorhexidine. Subjects participated in four experimental conditions: a pre-test, a quinine treatment, a chlorhexidine treatment, and a post-test condition, while rating total taste intensity and taste qualities in separate test sessions. Relative to the quinine treatment, chlorhexidine was found to decrease the salty taste of NaCl, KCl and NH4Cl, and not to significantly affect the tastes of sucrose, monosodium glutamate (MSG), citric acid, HCl and the taste of water. The bitter taste of urea, sucrose octa-acetate and quinine were suppressed after chlorhexidine rinses relative to water rinses, but were only marginally suppressed relative to quinine rinses. Potential mechanisms are discussed.     

Measures of individual differences in taste and creaminess perception

Previous reports that the sensitivity to the bitter tasting substance 6-n-propylthiouracil (PROP) is related to the sensitivity to other tastes, to chemical irritants, and to fats and oils have led to adoption of PROP as a measure of general oral sensitivity and as a predictor of dietary habits that could impact health. The results, however, have not been consistent. It was recently discovered that the ability to perceive "thermal taste" (i.e., sweetness from thermal stimulation alone) was associated with higher responsiveness to 4 prototypical taste stimuli but not to PROP. This finding implied that individual differences in taste perception are determined in large part by factors other than those related to genetic expression of the PROP receptor. The present study followed up this observation by comparing individual differences in perception of 4 prototypical taste stimuli (sucrose, NaCl, citric acid, and quinine) and PROP under conditions that also enabled assessment of the reliability of individual intensity ratings of taste. Creaminess ratings of 3 milk products that had different fat contents were also collected to investigate further the relationship between taste and oral somatosensory perception. The results showed that intensity ratings across 2 trials were significantly correlated for all 5 taste stimuli and that averaging across replicates led to significant correlations among the 4 prototypical stimuli. In contrast, the bitterness of PROP was correlated only with the bitterness of quinine. None of the taste stimuli, including PROP, was significantly correlated with ratings of creaminess. These results imply 1) that with the exception of PROP, as few as 2 intensity ratings of common taste stimuli can reveal individual differences in overall taste perception and 2) that any relationship between taste and oral sensation is too weak to be detected under the same conditions. Accordingly, the results support other evidence that the genetic factors which determine the ability to perceive PROP do not play a major role in overall taste and oral somatosensory perception.     

Tactile interaction with taste localization: influence of gustatory quality and intensity

Taste is always accompanied by tactile stimulation, but little is known about how touch interacts with taste. One exception is evidence that taste can be "referred" to nearby tactile stimulation. It was recently found (Lim J, and Green BG. 2007. The psychophysical relationship between bitter taste and burning sensation: evidence of qualitative similarity. Chem Senses. 32:31-39) that spatial discrimination of taste was poorer for bitterness than for other tastes when the perceived intensities were matched. We hypothesized that this difference may have been caused by greater referral of bitterness by touch. The present study tested this hypothesis by comparing localization of quinine sulfate and sucrose under conditions that minimized and maximized the opportunity for referral. In both conditions, stimulation was produced by 5 cotton swabs spaced 1 cm apart and arranged in an arc to enable simultaneous contact with the front edge of the tongue. Only one swab contained the taste stimulus, whereas the rest were saturated with deionized water. In both conditions, the swabs were stroked up-and-down against the tongue 5 times. Subjects were asked to identify which swab contained the taste stimulus 1) 5 s after the fifth stroke (touch-removed condition) and 2) immediately at the end of the fifth stroke, with the swabs still in contact with the tongue (touch-maintained condition). Ratings of taste intensity were obtained to assess the possible effect of perceived intensity on spatial localization. Taste localization was surprisingly accurate, especially for sucrose, with errors of localization in the range of 1 cm or less. For both stimuli, localization tended to be poorer when the tactile stimulus was present while subjects made their judgments, but the difference between conditions was significant only for the lower concentration of quinine. The results are discussed in terms of both the surprisingly good spatial acuity of taste and the possibility of having a close perceptual relationship between touch and bitter taste.     

Inducibility of Aryl Hydrocarbon Hydroxylase Activity in Cultured Cell as Food-screening for Safety Assessment

In order to investigate the effect of leucine residues on the taste of peptides, some oligo peptides containing leucine residues were synthesized and their taste was evaluated. The hydrophobicity of leucine residues markedly caused the bitterness of peptides and stronger bitterness was always found when a leucine residue was located at the C-terminus of peptides. The possibility of 2 binding sites between the bitter peptides and the bitter taste receptors of the gustation cells was postulated.     

Riboflavin-binding protein is a novel bitter inhibitor

Riboflavin-binding protein (RBP) from chicken egg, which was recently reported to be a selective sweet inhibitor for protein sweeteners, was also found to be a bitter inhibitor. RBP elicited broadly tuned inhibition of various bitter substances including quinine-HCl, naringin, theobromine, caffeine, glycyl-L-phenylalanine (Gly-Phe), and denatonium benzoate, whereas several other proteins, such as ovalbumin (OVA) and beta-lactoglobulin, were ineffective in reducing bitterness of these same compounds. Both the bitter tastes of quinine and caffeine were reduced following an oral prerinse with RBP. It was found that RBP binds to quinine but not to caffeine, theobromine, naringin, and Gly-Phe. However, the binding of RBP to quinine was probably not responsible for the bitter inhibition because OVA bound to quinine as well as RBP. Based on these results, it is suggested that the bitter inhibitory effect of RBP is the consequence of its ability to interact with taste receptors rather than because it interacts with the bitter tastants themselves. RBP may have practical uses in reducing bitterness of foods and pharmaceuticals. It may also prove a useful tool in studies of mechanisms of bitter taste.     

Revisiting sugar-fat mixtures: sweetness and creaminess vary with phenotypic markers of oral sensation

Genetic variation in oral sensation presumably influences ingestive behaviors through sensations arising from foods and beverages. Here, we investigated the influence of taste phenotype [6-n-propylthiouracil (PROP) bitterness, fungiform papillae (FP) density] on sweet and creamy sensations from sugar/fat mixtures. Seventy-nine subjects (43 males) reported the sweetness and creaminess of water or milk (skim, whole, heavy cream) varying in sucrose (0-20% w/v) on the general Labeled Magnitude Scale. Sweetness grew with sucrose concentration and when shifting from water to milk mixtures--the growth was greatest for those tasting PROP as most bitter. At higher sucrose levels, increasing fat blunted the PROP-sweet relationship, whereas at lower levels, the relationship was effectively eliminated. Perceived sweetness of the mixture exceeded that predicted from the sum of components at low sucrose concentrations (especially for those tasting PROP most bitter) but fell below predicted at high concentrations, irrespective of fat level. Creaminess increased greatly with fat level and somewhat with sucrose. Those tasting PROP most bitter perceived greater creaminess in the heavy cream across all sucrose levels. Perceived creaminess was somewhat lower than predicted, irrespective of PROP bitterness. The FP density generally showed similar effects as PROP on sweetness and creaminess, (but to a lesser degree) and revealed potential taste-somatosensory interactions in weakly sweet stimuli. These data support that taste phenotype affects the nature of enhancement or suppression of sweetness and creaminess in liquid fat/sugar mixtures. Taste phenotype effects on sweetness and creaminess likely involve differential taste, retronasal olfactory, and somatosensory contributions to these perceptual experiences.     

Bitterness of Phenylalanine- and Tyrosine-containing Peptides

In order to investigate the role of phenylalanine and tyrosine residues in the bitter taste of peptides, some oligopeptides containing phenylalanine or tyrosine were synthesized and their taste was evaluated. The hydrophobicity of the phenylalanine or tyrosine molecule markedly caused the bitter taste in peptide. The bitterness was more intense when phenylalanine was located at the C- terminus and when the content of phenylalanine or tyrosine was increased in peptides. The hydrophobic residue in peptides functioned as a bitter taste determinant site. The experimental results suggest the existence of an additional site for the bitter taste of peptides.     

Bitter taste of saccharin and acesulfame-K.

The relationships among suprathreshold taste responses to acesulfame-K, Na-saccharin and 6-n-propylthiouracil (PROP) were examined in two studies. In the first study, the labeled magnitude scale was used with the high anchor labeled as 'strongest imaginable oral sensation' and in the second study, it was labeled as 'strongest imaginable sensation of any kind'. Results from the two procedures were similar. Individual differences among 65 subjects were seen in bitter responses to acesulfame-K and saccharin. Bitter responses to acesulfame-K ands accharin were positively correlated, but showed no significant relationship with responses to PROP bitterness or with PROP taster groups. Saccharin and acesulfame-K may share a common mechanism for bitter taste reception and transduction, one that varies across individuals and is different from mechanisms mediating bitter responses to PROP. Changing the instructions of the labeled magnitude scale induced a context effect. Ratings of sweetness referenced to the 'strongest imaginable sensationof any kind' were lower than ratings referenced to just oral sensations.     

Tolerance of bitter stimuli and attenuation/accumulation of their bitterness in humans

Some components of bitterness make key flavor contributions to promote the palatability of foods, whereas other components are recognized as aversive signals to avoid consuming harmful substances. These contradictory behaviors suggest that humans tolerate tastes of bitterants based on certain criteria. Here, we investigated human taste tolerance and sensory cues leading to diverse taste tolerance of bitter compounds. Tolerance of eight bitter compounds, which are typically contained in foods, was evaluated by measuring detection and rejection thresholds. The results revealed that the level of tolerance of each compound was variable, and some compounds showed an acceptable concentration regarding the suprathreshold intensity. Tolerance did not depend on the nutritive value or attenuation and accumulation characteristics of bitterness and bitter taste receptors. These results suggest that the criteria controlling tolerance of bitter compounds may be derived from a complex relationship between the taste quality and cognitive process.     

Taste masking of ondansetron hydrochloride by polymer carrier system and formulation of rapid-disintegrating tablets

The purpose of this research was to mask the intensely bitter taste of ondansetron HCl and to formulate a rapiddisintegrating tablet (RDT) of the taste-maske drug. Taste masking was done by complexing ondansetron HCl with aminoalkyl methacrylate copolymer (Eudragit EPO) in different ratios by the precipitation method. Drug-polymer complexes (DPCs) were tested for drug content, in vitro taste in simulated salivary fluid (SSF) of pH 6.2, and molecular property. Complex that did not release drug in SSF was considered taste-masked and selected for formulation RDTs. The complex with drug-polymer ratio of 8∶2 did not show drug release in SSF; therefore, it was selected. The properties of tablets such as tensile strength, wetting time, water absorption ratio, in vitro disintegration time, and disintegration in the oral cavity were investigated to elucidate the wetting and disintegration characteristics of tablets. Polyplasdone XL-10 7% wt/wt gave the minimum disintegration time. Tablets of batch F4 containing spray-dried mannitol and microcrystalline cellulose in the ratio 1∶1 and 7% wt/wt Polyplasdone XL-10 showed faster disintegration, within 12.5 seconds, than the marketed tablet (112 seconds). Good correlation between in vitro disintegration behavior and in the oral cavity was recognized. Taste evaluation of RDT in human volunteers revealed considerable taste masking with the degree of bitterness below threshold value (0.5) ultimately reaching to 0 within 15 minutes, whereas ondansetron HCl was rated intensely bitter with a score of 3 for 10 minutes. Tablets of batch F4 also revealed rapid drug release (t₉₀, 60 seconds) in SGF compared with marketed formulation (t₉₀, 240 seconds;P<.01). Thus, results conclusively demonstrated successful masking of taste and rapid disintegration of the formulated tablets in the oral cavity. Published: June 22, 2007     

灵长类苦味受体基因研究进展

在鲜味、甜味、苦味、咸味和酸味5种味觉形式中,苦味能避免动物摄入有毒有害物质,在动物的生存中发挥着特别重要的作用。苦味味觉的产生依赖于苦味物质与苦味受体的相互作用。苦味受体由苦味受体基因Tas2rs编码,此类基因在不同物种中数量变化较大以适应不同的需求。目前的研究在灵长类中鉴别出了若干苦味受体的配体,并发现有的苦味受体基因所经受的选择压在类群之间、基因之间甚至同一基因不同功能区之间都存在着变化。本文从苦味受体作用的多样性特点,受体与配体的对应关系、受体基因进化模式与食性之间的关系、苦味受体基因的适应性进化方面对灵长类苦味受体基因进行了综述,以期为苦味受体基因在灵长类中的深入研究提供参考。     

Evaluation of the bitterness of green tea catechins by a cell-based assay with the human bitter taste receptor hTAS2R39

Catechins have a broad range of physiological functions and act as the main taste ingredient of green tea. Although catechins show a strong bitterness, the bitter taste receptor for catechins has not been fully understood. The objective of this study was to identify the receptor for the major green tea catechins such as (−)-epicatechin (EC), (−)-epicatechin gallate (ECg), (−)-epigallocatechin (EGC), and (−)-epigallocatechin gallate (EGCg). By the cell-based assay using cultured cells expressing human bitter taste receptor, a clear response of hTAS2R39-expressing cells was observed to 300 μM of either ECg or EGCg, which elicit a strong bitterness in humans. The response of hTAS2R39-expressing cells to ECg was the strongest among the tested catechins, followed by EGCg. Because the cellular response to EC and EGC is much weaker than those of ECg and EGCg, galloyl groups was strongly supposed to be involved in the bitter intensity. This finding is similar to the observations of taste intensity obtained from a human sensory study. Our results suggest the participation of hTAS2R39 in the detection of catechins in humans, indicating the possibility that bitterness of tea catechins can be evaluated by using cells expressing hTAS2R39.     

Specific alleles of bitter receptor genes influence human sensitivity to the bitterness of aloin and saccharin

Variation in human taste is a well-known phenomenon. However, little is known about the molecular basis for it. Bitter taste in humans is believed to be mediated by a family of 25 G protein-coupled receptors (hT2Rs, or TAS2Rs). Despite recent progress in the functional expression of hT2Rs in vitro, up until now, hT2R38, a receptor for phenylthiocarbamide (PTC), was the only gene directly linked to variations in human bitter taste. Here we report that polymorphism in two hT2R genes results in different receptor activities and different taste sensitivities to three bitter molecules. The hT2R43 gene allele, which encodes a protein with tryptophan in position 35, makes people very sensitive to the bitterness of the natural plant compounds aloin and aristolochic acid. People who do not possess this allele do not taste these compounds at low concentrations. The same hT2R43 gene allele makes people more sensitive to the bitterness of an artificial sweetener, saccharin. In addition, a closely related gene's (hT2R44's) allele also makes people more sensitive to the bitterness of saccharin. We also demonstrated that some people do not possess certain hT2R genes, contributing to taste variation between individuals. Our findings thus reveal new examples of variations in human taste and provide a molecular basis for them.