Synthesis and self-assembly behaviors of α-galactosyl ceramide (1,2)-polysaccharide analogue.

α-Galactosyl ceramide (GalCer) as a glycolipid has been long used as a standard reference for positive control in natural killer T cell studies. The (1,2)-disaccharide analogue of GalCer attracts a special attention in the study of lysosomal glycolipid processing. This paper describes the synthesis and self-assembly behaviors of GalCer 1,2-polysaccharide analogue (PolyGalCer), having considered the 1,2-disaccharide analogue as a structural motif. The synthesis of PolyGalCer is performed via one-pot glycosidation technique of 1,2-linked oligogalactan exploiting chain polymerization of galactose-based cyclic sulfite as a monomer initiated with ceramide-based alcoholic aglycon. Through the concentration dependence of PolyGalCer solutions in water or in MeOH on the turbidity, it is found that PolyGalCer forms associates in both media. From the intersection points, the critical aggregation concentration (CAC) values of PolyGalCer in water and MeOH were estimated. To know the self-assembly and the thermal transition behaviors, we performed dynamic light scattering (DLS) analysis of the associates comprising PolyGalCer in water. The transmission electron microscopy observations of the aqueous sample solution indicate that the solution of PolyGalCer includes large spherical associates. The results clarify that the 1,2-galactan moiety of PolyGalCer skeleton contributes on the kinetic inhibition of large associate formation and the metamorphosis of associates.

Dansylated Nitrile N-Oxide as the Fluorescent Dye Clickable to Unsaturated Bonds without Catalyst.

Fluorescent polymeric materials have been exploited in the fields of aesthetical purposes, biomedical engineering, and three-dimensional printing applications. While the fluorescent materials are prepared by the polymerization of fluorescent monomer or the blending a fluorescent dye with common polymer, the covalent immobilization of fluorescent dye onto common polymers is not the practical technique. In this paper, dansylated nitrile N-oxide (Dansyl-NO) has been designed and synthesized to be a stable nitrile N-oxide as the derivative of 2-hydroxy-1-naphthaldehyde. While Dansyl-NO shows good reactivity to an alkene and an alkyne to give fluorescent Dansyl-Ene and Dansyl-Yne, respectively, it hardly reacts to a nitrile. The results indicate that Dansyl-NO serves as a fluorescent dye clickable to alkenes and alkynes. To know the effects of solvent on the fluorescent properties, the UV-vis and fluorescence spectra of Dansyl-Ene are measured in three solvents. Dansyl-Ene shows fluorescent solvatochromism, which appears to be red-shifted along with the increase in solvent polarity. Poly(styrene-co-butadiene) directly reacts with Dansyl-NO to give fluorescent modified SB. The emission spectrum of modified SB is blue-shifted compared with that of Dansyl-Ene. The blue-shift could be possibly attributed to the presence of less polar polymer skeleton around the dansyl moieties of modified SB.

Background factors of idiopathic peptic ulcers and optimal treatment methods: a multicenter retrospective Japanese study.

This study investigated the trends in idiopathic peptic ulcers, examined the characteristics of refractory idiopathic peptic ulcer, and identified the optimal treatment. The characteristics of 309 patients with idiopathic peptic ulcer were examined. We allocated idiopathic peptic ulcers that did not heal after 8 weeks' treatment (6 weeks for duodenal ulcers) to the refractory group and those that healed within this period to the healed group. The typical risk factors for idiopathic peptic ulcer (atherosclerosis-related underlying disease or liver cirrhosis complications) were absent in 46.6% of patients. Absence of gastric mucosal atrophy (refractory group: 51.4%, healed group: 28.4%; p = 0.016), and gastric fundic gland polyps (refractory group: 17.6%, healed group: 5.9%; p = 0.045) were significantly more common in the refractory group compared to the healed group. A history of H. pylori eradication (refractory group: 85.3%, healed group: 66.0%; p = 0.016), previous H. pylori infection (i.e., gastric mucosal atrophy or history of H. pylori eradication) (refractory group: 48.5%, healed group: 80.0%; p = 0.001), and potassium-competitive acid blocker treatment (refractory group: 28.6%, healed group, 64.1%; p = 0.001) were significantly more frequent in the healed group compared to the refractory group. Thus, acid hypersecretion may be a major factor underlying the refractoriness of idiopathic peptic ulcer.

Synthesis and Conformational Behaviors of Unnatural Peptides Alternating Chiral and Achiral α,α-Disubstituted α-Amino Acid Units.

The development of peptidomimetics to modulate the conformational profile of peptides has been extensively studied in the fields of biological and medicinal chemistry. However, large-scale synthesis of peptidomimetics with both an ordered sequence and a controlled secondary structure is highly challenging. In this paper, the framework of peptidomimetics has been designed to be alternating an achiral α,α-disubstituted α-amino acid unit and a chiral α-methylphenylalanine unit. The polymers are synthesized via invented Ugi reaction-based polycondensation technique. The chiral higher-order structures of the alternating peptides are evaluated mainly through circular dichroism (CD) spectroscopy. The UV-Vis and CD spectra of the polymers in three solvents are systematically measured at various temperatures. The anisotropic factors of CD (gCD ) values are calculated to know the chiroptical response. The results indicate the characteristic conformational behaviors. In a polar solvent, the hydrogen bonds between the N-H group of MePhe unit and the C=O of α,α-diphenylglycine unit outweigh the intraresidue hydrogen bonds in α,α-diphenylglycine unit, leading to the formation of a prevailing preferred-handed 310 -helical conformation. On the other hand, in a less polar solvent, the intrachain hydrogen bonds switch to intraresidue hydrogen bonds in α,α-diphenylglycine unit, which make the polymer adopting a prevailing extended planar C5 -conformation.

Treating an Intractable Jejunocutaneous Fistula by Endoscopic Metallic Stent Placement: A Case Report of Successful Palliative Endoscopic Treatment in a Case Demonstrating Peritoneal Dissemination with Terminal Stage Gastric Cancer.

A 74-year-old woman with recurrent gastric cancer underwent laparotomy for peritoneal dissemination, and the damaged jejunum formed a jejunocutaneous fistula. Because conservative treatment alone could not cure the fistula, we performed an endoscopic placement of a partially covered self-expandable metallic stent (SEMS) to cover the fistula. After the procedure, the contrast medium no longer leaked from the intestinal lumen. One month after stent placement, the cutaneous opening had closed. This case report demonstrates the potential for using partially covered SEMS to treat intractable jejunocutaneous fistula in patients with terminal-stage malignant tumors.

Betulin Attenuates TGF-ß1- and PGE2-Mediated Inhibition of NK Cell Activity to Suppress Tumor Progression and Metastasis in Mice.

Transforming growth factor (TGF)-ß1 and prostaglandin E2 (PGE2) are humoral factors critically involved in the induction of immunosuppression in the microenvironment of various types of tumors, including melanoma. In this study, we identified a natural compound that attenuated TGF-ß1- and PGE2-induced immunosuppression and examined its effect on B16 melanoma growth in mice. By screening 502 natural compounds for attenuating activity against TGF-ß1- or PGE2-induced suppression of cytolysis in poly(I:C)-stimulated murine splenocytes, we found that betulin was the most potent compound. Betulin also reduced TGF-ß1- and PGE2-induced downregulation of perforin and granzyme B mRNA expression and cell surface expression of NKG2D and CD69 in natural killer (NK) cells. Cell depletion and coculture experiments showed that NK cells, dendritic cells, B cells, and T cells were necessary for the attenuating effects of betulin. Structure-activity relationship analysis revealed that two hydroxyl groups at positions C3 and C28 of betulin, their cis-configuration, and methyl group at C30 played crucial roles in its attenuating activity. In a subcutaneous implantation model of B16 melanoma in mice, intratumor administration of betulin and LY2157299, a TGF-ß1 type I receptor kinase inhibitor, significantly retarded the growth of B16 melanoma. Notably, betulin increased significantly the number of CD69 positive NK cells in tumor sites at early stages of post-tumor cell injection. Our data suggest that betulin inhibits the growth of B16 melanoma by enhancing NK cell activity through attenuating the immunosuppressive tumor microenvironment.

Severe Anemia Caused by Gastric Antral Vascular Ectasia and Autoimmune Gastritis.

An 80-year-old man presented to our hospital with general fatigue on exertion that had gradually worsened over 6 months. His blood test revealed severe anemia, and gastroscopy revealed findings consistent with gastric antral vascular ectasia (GAVE) and autoimmune gastritis. We diagnosed the patient with severe anemia caused by GAVE and autoimmune gastritis. The present case suggested that GAVE is triggered by autoimmune gastritis, and the mechanism is likely related to hypergastrinemia. The reporting of this rare case may help elucidate the cause of GAVE, which is currently unknown.

Tannin-phytobezoars with Gastric Outlet Obstruction Treated by Dissolution with Administration and Endoscopic Injection of Coca-Cola®, Endoscopic Crushing, and Removal (with Video).

A 77-year-old man complained of postmeal vomiting and sustained general fatigue. An abdominal computed tomography scan showed massive gastric expansion and fluid storage. Gastroscopy revealed four gastric bezoars that were considered to have caused pyloric ring obstruction. The patient was asked to drink 500 mL per day of Coca-Cola® for 4 days. On the fourth day, we performed endoscopic crushing and removal by injecting Coca-Cola®, cutting the softened bezoar with endoscopic snares, and collecting the pieces with endoscopic nets. We herein report (with a video presentation) a rare case of tannin-phytobezoars endoscopically removed with the administration and injection of Coca-Cola®.

Effects of Glycon and Temperature on Self-Assembly Behaviors of α-Galactosyl Ceramide in Water.

α-Galactosyl ceramide (GalCer) is an anticancer glycolipid consisting of d-galactose and phytosphingosine-based ceramide. Although the amphiphilic structure of GalCer is expected to form self-associates in water, the self-assembly behaviors of GalCer and its derivatives have not been systematically investigated at this moment in spite of its great importance. The evaluation of morphologies and properties of the associates should open new insights into glycolipid chemistry such as the application of GalCer derivatives to a nanocarrier and the elucidation of the detailed pharmacological mechanism of GalCer. Herein, we show the synthesis of the aglycon fragment (Aglycon) of GalCer and the self-assembly behaviors of both GalCer and Aglycon in water. The critical aggregation concentrations of Aglycon and GalCer were determined using UV-vis spectral measurements at various concentrations. The transmission electron microscopy observations of the aqueous sample solutions indicated that the solution of GalCer includes vesicles, while that of Aglycon comprises giant micelles in the absence of vesicles. The vesicle formation in the solution of GalCer was also confirmed by Triton X-100-triggered dye-release experiments. To reveal the effects of glycon on the self-assembly behaviors in detail, we performed the measurements of dynamic light scattering, temperature-dependence of turbidity, differential scanning calorimetry, and wide-angle X-ray diffraction. The results clarify that the glycon moiety of GalCer has a significant role in the formation inhibition of second associates and the plasticization of the hydrophobe. This work will shed light on the other natural glycosides to evaluate the self-assembly behaviors for supramolecular and pharmacological applications in the near future.

Computational Analysis of the Selective Formation of the C4α-C8' Bond in the Intermolecular Coupling of Catechin Derivatives.

Procyanidin B3 is a natural flavonoid composed of two catechins connected via a C4α-C8' bond. The couplings of catechin derivatives, promoted by Lewis acids, have been widely applied to the syntheses of procyanidin B3 and related flavonoids because the reactions construct the C4α-C8' bond in a highly stereo- and regioselective manner. However, the structural complexity of the catechin derivatives has complicated the exploration of a detailed mechanism for this selectivity. Here, we report the results of a computational study to provide plausible origins for the selective C4α-C8' bond formation of catechin derivatives 1 and 2 by using models 5 and 7. Although a systematic search did not provide SN2-like transition states, we successfully identified transition states TS-A, TS-B, and TS-C for the SN1-type C4α-C8', C4ß-C8', and C4α-C6' bond formations, respectively, from a total of 233 transition states to justify the stereo- and regioselectivity of the experimental results. The analysis of these structures by NCIPLOT mapping and the distortion/interaction strain model suggests that the eclipsed interaction at the forming C-C bond between the electrophile and the nucleophile destabilizes TS-B, while the strain of the electrophile destabilizes TS-C. Consequently, the C4α-C8' bond is formed via the lowest energy transition state TS-A.

Biomimetic Oxidation of Monolignol Acetate and p-Coumarate by Silver Oxide in 1,4-Dioxane.

Lignin acylated with acetate and/or p-coumarate is common in many herbaceous plants. Herein, the biomimetic oxidation of γ-acylated monolignols with Ag2O was studied to understand the effect of γ-acyl groups on monolignol polymerization. The oxidation of sinapyl acetate gave γ-acylated and α-acylated ß-O-4 dimers in 71 and 9.5% yields, respectively. The oxidation of sinapyl p-coumarate produced γ-acylated ß-O-4 and γ-acylated tetralin ß-ß dimers in 53 and 16% yields, respectively. Only the sinapyl alcohol moiety in sinapyl p-coumarate reacted, and the p-coumarate moiety remained unchanged, suggesting that p-coumaric acid is not incorporated into the lignin backbone in the acylated lignins. All of the γ-acylated monolignols used in this study produced the γ-acylated ß-O-4 dimers, which suggests that the γ-acylated monolignols act as lignin monomers. The relatively high yields of the ß-O-4 dimers indicate that Ag2O oxidation of the monolignols can be used as an easy method for synthesizing the ß-O-4 dimer model compounds.

A Computational Study on the Stereo- and Regioselective Formation of the C4α-C6' Bond of Tethered Catechin Moieties by an Exhaustive Search of the Transition States.

We previously reported the total synthesis of procyanidin B6 by using the stereo- and regioselective C-C bond formation of tethered catechin moieties as the key step. The reaction afforded the product bearing a new C4α-C6' bond linkage instead of the inherently preferable C4α-C8' bond. However, the origin of this selectivity remained unclear due to the complex structure of the substrate. Here we report the results of computational exploration of this C-C bond formation to gain mechanistic insights into the selectivity. The computational study of highly flexible compounds was realized by an exhaustive search of transition states. A large library of candidate transition states was generated by a conformational search of constrained models using molecular mechanics simulations and semiempirical molecular orbital calculations. Subsequent DFT-based transition state calculations provided 367 transition states for C4-C6' and C4-C8' bond formations. Comparison of the geometries and energies showed that the C4α-C6' linkage is preferentially formed via two competing transition states, leading to a C6'-diastereomeric mixture. Interactive atomic distances and visualization of the nonbonding interactions suggest the importance of nonclassical hydrogen bonding and CH-π, π-π, and lone pair-π interactions in stabilizing the two transition states. The present study supports preferential C4α-C6' bond formation of the tethered catechins.

Lymphatic metabolites of quercetin after intestinal administration of quercetin-3-glucoside and its aglycone in rats.

Quercetin is a major flavonoid, present as its glycosidic forms in plant foods. In this study, quercetin-3-glucoside (Q3G) was administered intraduodenally to thoracic lymph-cannulated rats, and its lymphatic transport was investigated. The resulting lymphatic and plasma metabolites were identified with LC-MS/MS and compared with those after administration of quercetin aglycone. The total concentration of quercetin metabolites in the lymph was about four times lower than that in the plasma, and quercetin and its methylated form isorhamnetin were detected as their glucuronides, sulfates and diglucuronides both in the lymph and the plasma after Q3G and quercetin administrations. The lymph levels of the glucuronides after Q3G administration were lower than those after quercetin administration, whereas those in the plasma showed the opposite pattern. Both the lymph and plasma levels of the sulfates after Q3G administration were lower than those after quercetin administration. Some of the intestinal metabolites like quercetin monoglucuronides were transported directly into the lymph and the hepatic metabolites like the diglucuronides were eventually transferred from the plasma into the lymph. These results indicate that the absorbed Q3G is partly transported into the intestinal lymph as quercetin metabolites. Deglycosylation in the enterocyte is also suggested to affect the subsequent metabolic pathways.

Regioselective Synthesis of Procyanidin B6, A 4-6-Condensed (+)-Catechin Dimer, by Intramolecular Condensation.

Proanthocyanidins, also known as condensed tannins or oligomeric flavonoids, are found in many edible plants and exhibit interesting biological activities. Herein, we report a new, simple method for the stereoselective synthesis of procyanidin B6, a (+)-catechin-(4-6)-(+)-catechin dimer, by Lewis acid-catalyzed intramolecular condensation. The 5-O-t-butyldimethylsilyl (TBDMS) group of 5,7,3'4'-tetra-O-TBDMS-(+)-catechin was regioselectively removed using trifluoroacetic acid, leading to the "regio-controlled" synthesis of procyanidin B6. The 5-hydroxyl group of the 7,3',4'-tri-O-TBDMS-(+)-catechin nucleophile and the 3-hydroxyl group of 5,7,3',4'-tetra-O-benzylated-(+)-catechin electrophile were connected with an azelaic acid. The subsequent SnCl4-catalyzed intramolecular condensation proceeded smoothly to give the 4-6-condensed catechin dimer. This is the first report on the complete regioselective synthesis of a 4-6-connected oligomer without modifying the 8-position.

Biosynthesis of Drug Glucuronide Metabolites in the Budding Yeast Saccharomyces cerevisiae.

Glucuronidation is one of the most common pathways in mammals for detoxification and elimination of hydrophobic xenobiotic compounds, including many drugs. Metabolites, however, can form active or toxic compounds, such as acyl glucuronides, and their safety assessment is often needed. The absence of efficient means for in vitro synthesis of correct glucuronide metabolites frequently limits such toxicological analyses. To overcome this hurdle we have developed a new approach, the essence of which is a coexpression system containing a human, or another mammalian UDP-glucuronosyltransferases (UGTs), as well as UDP-glucose-6-dehydrogenase (UGDH), within the budding yeast, Saccharomyces cerevisiae. The system was first tested using resting yeast cells coexpressing UGDH and human UGT1A6, 7-hydroxycoumarin as the substrate, in a reaction medium containing 8% glucose, serving as a source of UDP-glucuronic acid. Glucuronides were readily formed and recovered from the medium. Subsequently, by selecting suitable mammalian UGT enzyme for the coexpression system we could obtain the desired glucuronides of various compounds, including molecules with multiple conjugation sites and acyl glucuronides of several carboxylic acid containing drugs, namely, mefenamic acid, flufenamic acid, and zomepirac. In conclusion, a new and flexible yeast system with mammalian UGTs has been developed that exhibits a capacity for efficient production of various glucuronides, including acyl glucuronides.

Structure-Activity Relationship of Oligomeric Flavan-3-ols: Importance of the Upper-Unit B-ring Hydroxyl Groups in the Dimeric Structure for Strong Activities.

Proanthocyanidins, which are composed of oligomeric flavan-3-ol units, are contained in various foodstuffs (e.g., fruits, vegetables, and drinks) and are strongly biologically active compounds. We investigated which element of the proanthocyanidin structure is primarily responsible for this functionality. In this study, we elucidate the importance of the upper-unit of 4-8 condensed dimeric flavan-3-ols for antimicrobial activity against Saccharomyces cerevisiae (S. cerevisiae) and cervical epithelioid carcinoma cell line HeLa S3 proliferation inhibitory activity. To clarify the important constituent unit of proanthocyanidin, we synthesized four dimeric compounds, (-)-epigallocatechin-[4,8]-(+)-catechin, (-)-epigallocatechin-[4,8]-(-)-epigallocatechin, (-)-epigallocatechin-[4,8]-(-)-epigallocatechin-3-O-gallate, and (+)-catechin-[4,8]-(-)-epigallocatechin and performed structure-activity relationship (SAR) studies. In addition to antimicrobial activity against S. cerevisiae and proliferation inhibitory activity on HeLa S3 cells, the correlation of 2,2-diphenyl-l-picrylhydrazyl radical scavenging activity with the number of phenolic hydroxyl groups was low. On the basis of the results of our SAR studies, we concluded that B-ring hydroxyl groups of the upper-unit of the dimer are crucially important for strong and effective activity.

Biomimetic oxidative coupling of sinapyl acetate by silver oxide: preferential formation of ß-O-4 type structures.

Biomimetic oxidations of sinapyl alcohol and sinapyl acetate were carried out with Ag2O to better understand the high frequency of ß-O-4 structures in highly acylated natural lignins. The major products from the Ag2O oxidation of sinapyl alcohol were sinapyl aldehyde (14% yield), ß-O-4-coupled dimer (32% yield), and ß-ß-coupled dimer (3% yield). In contrast, the Ag2O oxidation of sinapyl acetate produced ß-O-4-coupled dimer in 66% yield. Oligomeric products with predominantly ß-O-4 structures were also obtained in 18% yield. The yield of the ß-O-4-coupled products from sinapyl acetate was much higher than that from sinapyl alcohol. Computational calculations based on density functional theory showed that the negative charge at Cß was significantly reduced by the γ-acetyl group. The computational calculations suggest that the Coulombic repulsion between Cß and O4 in sinapyl acetate radicals was significantly reduced by the γ-acetyl group, contributing to the preferential formation of ß-O-4 structures from sinapyl acetate.

Inhibitory activity of synthesized acetylated Procyanidin B1 analogs against HeLa S3 cells proliferation.

Proanthocyanidins, also known as condensed tannins and/or oligomeric flavonoids, occur in many edible plants and have various interesting biological activities. Previously, we reported a synthetic method for the preparation of various procyanidins in pure form and described their biological activities. Here, we describe the synthesis of procyanidin B1 acetylated analogs and discuss their inhibition activities against HeLa S3 cell proliferation. Surprisingly, the lower-unit acetylated procyanidin B1 strongly inhibited the proliferation of HeLa S3 cells. This molecule showed much stronger inhibitory activity than did epigallocatechin-3-O-gallate (EGCG), green tea polyphenol, and dimeric compounds that included EGCG as a unit. This result suggests that the phenolic hydroxyl groups of the upper-units in flavan-3-ols are important for their inhibitory activity against cancer cell proliferation and that a hydrophobic lower unit dimer enhances this activity.

Isolation of a new phlorotannin, a potent inhibitor of carbohydrate-hydrolyzing enzymes, from the brown alga Sargassum patens.

Ethanol extracts from 15 kinds of marine algae collected from the coast of the Noto Peninsula in Japan were examined for their inhibitory effects on human salivary α-amylase. Four extracts significantly suppressed the enzyme activity. An inhibitor was purified from the extract of Sargassum patens . The compound was a new phloroglucinol derivative, 2-(4-(3,5-dihydroxyphenoxy)-3,5-dihydroxyphenoxy) benzene-1,3,5-triol (DDBT), which strongly suppressed the hydrolysis of amylopectin by human salivary and pancreatic α-amylases. The 50% inhibitory activity (IC(50)) for α-amylase inhibition of DDBT (3.2 µg/mL) was much lower than that of commercially available α-amylase inhibitors, acarbose (26.3 µg/mL), quercetagetin (764 µg/mL), and α-amylase inhibitor from Triticum aestivum (88.3 µg/mL). A kinetic study indicated that DDBT was a competitive α-amylase inhibitor with a K(i) of 1.8 µg/mL. DDBT also inhibited rat intestinal α-glucosidase with an IC(50) value of 25.4 µg/mL for sucrase activity and 114 µg/mL for maltase activity. These results suggest that DDBT, a potent inhibitor of carbohydrate-hydrolyzing enzymes, may be useful as a natural nutraceutical to prevent diabetes.