The Inhibitory Effect of Adenylic Acid on the Bitterness of the Antibacterial Combination Drug Trimethoprim/Sulfamethoxazole.

The purpose of the present study was to evaluate bitterness suppression effect of adenylic acid (AMP) as a nucleotide-derived nutrient enhancer on a bitter commercial drug. In the present study, we evaluated peripheral bitterness inhibition effect of AMP on the trimethoprim (TMP) and sulfamethoxazole (SMZ) combination formulation based on taste sensor. The taste sensor values of TMP solutions with different concentrations show large sensor output in correlation with the concentration of TMP, whereas no sensor output in shown for the SMZ solutions. Therefore, the bitterness of this combination formulation is mainly due to TMP. We evaluated the TMP bitterness inhibitory effects of AMP, sodium salt of AMP (AMP Na; sodium adenylate), sodium salt of GMP (GMP Na; sodium guanylate), and sodium salt of inosine monophosphate (IMP Na; sodium inosinate), and found that only AMP displayed very effective bitterness inhibition. MarvinSketch analysis revealed that potential electrostatic interaction between cationized TMP and anionized forms (II and III) of AMP may cause bitterness suppression. 1H-NMR study suggested an interaction of TMP and AMP molecules based on chemical shift perturbations and an interaction between the phosphate group of AMP and amino group of TMP. Lastly, conventional elution analysis simulating oral cavity capacity for up to one minute were performed using commercial TMP/SMZ combination granules. The sensor output gradually increased up to 60 s. The addition of AMP solution to the eluted sample at 60 s significantly decreased the bitterness sensor output of the eluted sample.

Masking the Taste of Fixed-Dose Combination Drugs: Particular NSAIDs Can Efficiently Mask the Bitterness of Famotidine.

This study aimed to evaluate the bitterness of famotidine (FAM) combined with each of three non-steroidal anti-inflammatory drugs (NSAIDs): ibuprofen (IBU), flurbiprofen (FLU), and naproxen (NAP), which have potential as fixed-dose combination (FDC) drugs. We evaluated the bitterness of FAM and each NSAID by taste sensor AN0 and C00, respectively. FAM showed high sensor output representing sensitivity to bitterness, whereas three NSAIDs did not show large sensor output, suggesting that the bitterness intensities of three NSAIDs were lower than that of FAM. The bitterness of FAM on sensor AN0 was suppressed in a concentration-dependent manner when mixed with IBU, FLU, or NAP. Among three NSAIDs, IBU most effectively inhibited bitterness on sensor output, and the gustatory sensation test confirmed that adding IBU to FAM reduced the bitterness of FAM in a concentration-dependent manner. MarvinSketch confirmed that the drugs were mostly present in an ionic solution when FAM was mixed with NSAIDs. The 1H-NMR spectroscopy analysis also revealed the presence of electrostatic interactions between FAM and NSAIDs, suggesting that the electrostatic interaction between FAM and NSAIDs might inhibit the adsorption of FAM on the bitter taste sensor membrane, thereby masking the bitter taste.

Construction of Acyclic All-Carbon Quaternary Stereocenter Based on Asymmetric Michael Addition of Chiral Amine.

Acyclic asymmetric quaternary stereocenters, which are composed of four carbon-carbon bonds, were finely constructed by utilizing a face-selective alkylation of enolate intermediates derived from an asymmetric Michael addition reaction of a chiral lithium amide with trisubstituted (E)-α,ß-unsaturated esters. The present face-selective alkylation was able to employ diverse alkyl halides as an electrophile to afford various Michael adducts having an all-carbon quaternary stereocenter. With regard to the deprotection of the chiral auxiliary, N-iodosuccinimide used in our previous study did not work in the present cases; however, we found that pyridine iodine monochloride in the presence of H2O was effective to remove the bornyl group and the benzyl group on the amino group to provide the ß-amino ester derivative.

Antimicrobial Activities of LL-37 Fragment Mutant-Poly (Lactic-Co-Glycolic) Acid Conjugate against Staphylococcus aureus, Escherichia coli, and Candida albicans.

Various peptides and their derivatives have been reported to exhibit antimicrobial activities. Although these activities have been examined against microorganisms, novel methods have recently emerged for conjugation of the biomaterials to improve their activities. Here, we prepared CKR12-PLGA, in which CKR12 (a mutated fragment of human cathelicidin peptide, LL-37) was conjugated with poly (lactic-co-glycolic) acid (PLGA), and compared the antimicrobial and antifungal activities of the conjugated peptide with those of FK13 (a small fragment of LL-37) and CKR12 alone. The prepared CKR12-PLGA was characterized by dynamic light scattering and measurement of the zeta potential, critical micellar concentration, and antimicrobial activities of the fragments and conjugate. Although CKR12 showed higher antibacterial activities than FK13 against Staphylococcus aureus and Escherichia coli, the antifungal activity of CKR12 was lower than that of FK13. CKR12-PLGA showed higher antibacterial activities against S. aureus and E. coli and higher antifungal activity against Candida albicans compared to those of FK13. Additionally, CKR12-PLGA showed no hemolytic activity in erythrocytes, and scanning and transmission electron microscopy suggested that CKR12-PLGA killed and disrupted the surface structure of microbial cells. Conjugation of antimicrobial peptide fragment analogues was a successful approach for obtaining increased microbial activity with minimized cytotoxicity.

Preparation and Evaluation of Poly-γ-glutamic Acid Hydrogel Mixtures with Amlodipine Besylate: Effect on Ease of Swallowing and Taste Masking.

The purpose of the study was to prepare a poly-γ-glutamic acid hydrogel (PGA gel), to evaluate physicochemical properties, its ease of swallowing using texture profile analysis (TPA) and its taste-masking effects on amlodipine besylate (AML) using the artificial taste sensor and human gustatory sensation testing. Using TPA, 0.5 and 1.0% (w/v) PGA gels in the absence of drug were within the range of acceptability for use in people with difficulty swallowing according to permission criteria published by the Japanese Consumers Affairs Agency. The elution of AML from prepared PGA gels was complete within an hour and the gel did not appear to influence the bioavailability of AML. The sensor output of the basic bitterness sensor AN0 in response to AML mixed with 0.5 and 1.0% PGA gels was suppressed to a significantly greater degree than AML mixed with 0.5 and 1.0% agar. In human gustatory sensation testing, 0.5 and 1.0% PGA gels containing AML showed a potent bitterness-suppressing effect. Finally, 1H-NMR spectroscopic analysis was carried out to examine the mechanism of bitterness suppression when AML was mixed with PGA gel. The signals of the proton nearest to the nitrogen atom of AML shifted clearly upfield, suggesting an interaction between the amino group of AML and the carboxyl group of PGA gel. In conclusion, PGA gel is expected to be a useful excipient in formulations of AML, not only increasing ease of swallowing but also masking the bitterness of the basic drug.

Bitterness-Masking Effects of Different Beverages on Zopiclone and Eszopiclone Tablets.

The purpose of the study was to evaluate the ability of different beverages to mask the bitterness of zopiclone and eszopiclone in tablet formulations using the artificial taste sensor and human gustatory sensation testing. The beverages tested for bitterness-masking effects were: Mugicha, Sports beverage, Lactic acid drink, Orange juice and a diluted simple syrup (an 8.5% sucrose solution). The bitterness intensities estimated by the taste sensor of zopiclone or eszopiclone one-tablet solutions mixed with the various beverages, corresponded well with the observed bitterness intensities measured by gustatory sensation testing. The Sports beverage, Lactic acid drink and Orange juice significantly suppressed the bitterness intensity of both zopiclone and eszopiclone 1-tablet solutions compared with water when tested in the artificial taste sensor. Sports beverage, Lactic acid drink and Orange juice all contain citric acid as acidifier, so it was postulated that citric acid was involved in the mechanism of bitterness intensity suppression of zopiclone and eszopiclone 1-tablet solutions by these three beverages. It was then shown that citric acid suppressed the bitterness intensity of a zopiclone one-tablet sample solution in a dose-dependent manner. 1H-NMR spectroscopic analysis of mixtures of citric acid with zopiclone suggested that the carboxyl groups of citric acid interact with the amine group on zopiclone. This study therefore showed that the bitterness intensities of zopiclone and eszopiclone can be suppressed by citric-acid-contained beverages and suggests that this bitterness suppression is due to a direct electrostatic interaction between citric acid and the two drugs.

A Facile and Convenient Synthesis of Trisubstituted (E)-α,ß-Unsaturated Esters by Tandem Acetylation-E1cB Reaction.

A facile and convenient synthesis of trisubstituted (E)-α,ß-unsaturated esters was developed by improving our previously established method. The new method circumvented the separation of the intermediates, which have an activating group of the hydroxyl group in ß-hydroxy esters, furnishing α,ß-unsaturated esters in shorter steps than the previous method: an acetylation of ß-hydroxy group and subsequent E1cB reaction proceeded in tandem. In addition, the new method can not only employ a diastereomeric mixture of the substrate for the E1cB reaction, it has a wide substrate scope as well, which would enable the synthesis of various trisubstituted (E)-α,ß-unsaturated esters.

Reaction of 2a,8b-Dihydrobenzo[b]cyclobute[d]pyran-3-ones with Dimethylsulfoxonium Methylide.

Using dimethylsulfoxonium methylide as the methylene transfer reagent, 2a,8b-dihydrobenzo[b]cyclobute[d]pyran-3-ones were converted into 2,2'-biphenol derivatives as major products and dihydrodibenzofurans as minor products. The reaction mechanism was extrapolated from a deuteration experiment with CD2=S(O)(CD3)2.

Indole synthesis from N-allenyl-2-iodoanilines under mild conditions mediated by samarium(II) diiodide.

A novel method for indole skeleton synthesis under mild conditions mediated by samarium(ii) diiodide has been developed. The reaction of N-allenyl-2-iodoaniline derivatives with SmI2 in the presence of HMPA and i-PrOH at 0 °C afforded indole derivatives in high yields.

Synthesis of (±)-8-deisopropyladunctin B.

(±)-8-Deisopropyladunctin B, the deisopropyl form of adunctin B, which was isolated from the leaves of Piper aduncum (Piperaceae) collected in Papua New Guinea, was synthesized in 0.77% overall yield in 17 steps from 5,7-dimethoxycoumarin-3-carboxylate. The key step was our original stereoconvergent skeleton transformation from 1,2,2a,8b-tetrahydro-3H-benzo[b]cyclobuta[d]pyran-3-one to 1,2,4a,9b-tetrahydrodibenzofuran-4-ol with dimethylsulfoxonium methylide.

One-pot construction of multiple contiguous chiral centers using Michael addition of chiral amine.

Multiple contiguous chiral centers were constructed in one pot using three types of multistep reactions initiated with the Michael addition of N-benzyl-2(R)-methoxy-(+)-10-bornylamide to alpha,beta-unsaturated esters, i.e., asymmetric Michael-aldol reaction, double Michael addition, and double Michael-aldol reaction. The chiral 2-methoxy-10-bornyl group as well as the benzyl group on the amino group of the products in the Michael-aldol reaction could be easily cleaved by treatment with NIS (4 equiv), and beta-amino esters with multiple contiguous chiral centers were obtained in good yield. As an application, the beta-amino-beta'-hydroxy ester obtained in the asymmetric Michael-aldol reaction was converted to the beta-lactam derivative in good yield.

Efficient asymmetric synthesis of abeo-abietane-type diterpenoids by using the intramolecular Heck reaction.

The synthesis of the abeo-abietane-type diterpenoids, i.e., (-)-dichroanal B, (-)-dichroanone, and taiwaniaquinone H, was achieved by using the intramolecular asymmetric Heck reaction. Our synthetic routes required fewer steps and gave a much higher overall yield and ee within shorter steps than those for racemic and antipodal forms reported to date (10, 12, and 13 steps with an overall yield of 50%, 40%, and 39%, and 94%, 98%, and 98% ee, respectively).

Glycosylation from the non-reducing end using a combination of thioglycoside and glycosyl sulfoxide as the glycosyl donor and the acceptor.

A glycosylation reaction was performed using a combination of thioglycoside and glycosyl sulfoxide, which were prepared with odorless p-octyloxybenzenethiol, as a glycosyl donor and an acceptor, respectively. Promising results were obtained when p-octyloxylphenyl N-phthaloyl-D-thio-glucosaminide was activated with N-iodosuccinimide (NIS) and triflic acid (TfOH) for glycosylation of the hydroxyl group of the C-6 position of derivatives of D-glucosyl sulfoxide. Successive reduction of the resulting disaccharyl sulfoxides provided the corresponding thioglycosides, which could be used as the glycosyl donors in another glycosylation reaction to afford trisaccharides in good yield. The present method would be useful for the block synthesis of glycosyl donors in the total synthesis of blanched oligosaccharides, especially when N-acetylglucosamines are presented at the non-reducing ends.

Isolation and identification of a novel aromatic amine mutagen produced by the Maillard reaction.

To clarify the formation of mutagens in the Maillard reaction of glucose and amino acids, 20 amino acids were separately incubated with glucose in the presence or absence of hydroxyl radicals produced by the Fenton reaction. After 1 week at 37 degrees C and pH 7.4, the reaction mixtures of glucose and tryptophan with and without the Fenton reagent showed mutagenicity toward Salmonella typhimurium YG1024 in the presence of a mammalian metabolic system (S9 mix). To identify mutagens in the reaction mixture, blue rayon-adsorbed material from a mixture of glucose, tryptophan, and the Fenton reagent was separated by column chromatography using various solid and mobile phases, and one mutagen, which accounted for 18% of the total mutagenicity of the reaction mixture, was isolated. The chemical structure of the mutagen was determined to be 5-amino-6-hydroxy-8H-benzo[6,7]azepino[5,4,3-de]quinolin-7-one (ABAQ) on the basis of ESI mass, high-resolution APCI mass, (1)H NMR, (13)C NMR, and IR spectral analyses and chemical synthesis of the mutagen. The novel aromatic amine showed high mutagenicity toward S. typhimurium TA98 and YG1024 with S9 mix, inducing 857 revertants of TA98 and 6007 revertants of YG1024/microg, respectively. The mutagenicity of ABAQ was comparable to that of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine, which is a mutagenic and carcinogenic hetrocyclic amine in cooked meat and fish formed through the Maillard reaction at high temperature.

Asymmetric Michael addition of a recyclable chiral amine: inversion of stereoselectivity caused by the difference of ethereal solvents.

The Michael addition of a chiral amine [(-)- 6] to alpha,beta-unsaturated esters ( 4) was attained and the stereoselectivity was inverted by changing the solvent from diethyl ether to tetrahydrofuran when alpha,beta-unsaturated esters having an aromatic ring at the beta-position were employed. In addition, the chiral auxiliary in the Michael adducts ( 9A) was facilely removed with N-iodosuccinimide to afford beta-amino esters ( 10A) and 2-methoxy- d-bornylaldehyde ( 11), which can be reclaimed to the chiral amine ( 6) by reductive amination.

Novel skeleton transformation reaction of α-pyrone derivatives to spirobicyclo[3.1.0]hexane derivatives using dimethylsulfoxonium methylide.

By applying a skeleton transformation reaction using dimethylsulfoxonium methylide, a novel reaction was identified by which 5,6,7,8-tetrahydrocoumarin with the electron-withdrawing group at C3 was led to the spirobicyclo[3.1.0]hexane-cyclohexane derivative. Moreover, by establishing the scope of this reaction, it was confirmed that it is possible to apply this reaction to not only ring-fused α-pyrone derivatives but also alkyl-chain-substituted α-pyrone derivatives in moderate to good yields.

Novel approach to determining the absolute configurations at the C3-positions of various types of sterols based on an induced circular dichroism.

Circular dichroism (CD) spectra of the 2,2'-binaphthyl ester derived from Δ(5)-sterols showed not bisignate CD but diagnostic CD bands at around 210 and 240 nm. These bands might be attributable to an interaction between an olefinic chromophore and a binaphthyl one. Various types of unsaturated sterols were thus derivatized followed by complete hydrogenation, to give saturated sterols. As a result, CD spectra of the binaphthyl derivatives of the saturated sterols showed bisignate curves centered at 240 nm (3S(ß): positive chirality; 3R(α): negative one). This suggested a straightforward and practical method for discriminating the absolute stereogenic center at the C-3 positions of sterols based on an induced CD. This finding should contribute significantly to the analysis of metabolites of various types of sterols.