High-performance liquid chromatographic determination and metabolic study of sennoside a in daiokanzoto by mouse intestinal bacteria

Daiokanzoto (DKT, combination of rhubarb and glycyrrhiza), a Kampo medicine, is clinically effective for constipation. Sennoside A is well known to induce diarrhea. Sennoside A is a prodrug that is transformed into an active metabolite, rheinanthrone, by intestinal bacteria. In this study, we investigated the effects of glycyrrhiza on the activity of sennoside A metabolism in intestinal bacteria using mouse feces. A high-performance liquid chromatography (HPLC) method for the determination of sennoside A in incubation mixture of DKT with mouse feces was established. The retention time of sennoside A was 9.26±0.02 min with a TSKgel ODS-80TsQA column by linear gradient elution using a mobile phase containing aqueous phosphoric acid and acetonitrile and detection at 265 nm. We found that the activity of sennoside A metabolism in intestinal bacteria was significantly accelerated when glycyrrhiza, liquiritin or liquiritin apioside coexisted with sennoside A, whereas that of glycyrrhizin was not altered. This method is applicable for determination of the activity of sennoside A metabolism by anaerobic incubation of DKT with mouse feces.     

New Syntheses of Geiparvarin and 2,5-Dimethyl-3(2H)-furanone Via Co2 Mediated Bond Reorganization

A new synthesis of 3(2H)-furanones from 4-hydroxy-2-alkyn-1-one derivatives via CO₂ mediated bond reorganization has been developed to the preparation of an antitumor agent, geiparvarin and a constituent of flavors, 2,5-dimethyl-3(2H)-furanone.     

Reaction of Metal-Free Triorganogermyl Anions with Aldehydes

Hexaorganosilylgermane (2) reacted with aldehydes and ketones (1) in the presence of catalytic amounts of fluoride ion in THF or HMPA to give 1-(triorgano-germyl)alkyl alcohols (3).     

Electrokinetic supercharging preconcentration prior to CGE analysis of DNA: Sensitivity depends on buffer viscosity and electrode configuration

Aiming to high sensitivity DNA analysis by CGE, electrokinetic supercharging (EKS) approach was adopted in this article. EKS is known as an online preconcentration technique that combines electrokinetic sample injection (EKI) with transient ITP (tITP). Herein, two factors of buffer viscosity and electrode configuration were studied to further improve EKS performance. An ultralow‐viscosity Tris‐Boric acid‐EDTA (TBE) buffer solution, consisted of 2% low‐molecular‐weight hydroxypropyl methyl cellulose (HPMC) and 6% mannitol and with pH 8.0 adjusted by boric acid, was applied. The boric acid would make a complex with mannitol and generates borate polyanion, which acts as the leading ion for tITP process. The new electrode configuration, a Pt ring around capillary, was modified on Agilent CE system to lead large amount sample introduction during EKS. The standard DNA sample of φX174/HaeIII digest was used to evaluate the qualitative and quantitative abilities of the proposed strategy. The 170 000‐fold highly diluted sample at concentration of 3.0 ng/mL was enriched by EKS and detected by normal UV detection method. The obtained LOD of the weakest peak of 72 bp fragment was around 7.7 pg/mL, apparently improved more than 10 000‐fold in comparison with conventional CGE with UV detection.     

Synthesis and characterization of 6-[4-(trans -4-pentylcyclohexyl)phenoxy]hexyl acrylate homopolymer and copolymers

The compound 6-[4-(trans -4-pentylcyclohexyl)phenoxy]hexyl acrylate (2) was prepared and homopolymerized. The block copolymer and copolymer of 2 with styrene were synthesized by photopolymerization and solution techniques, respectively. These polymers were characterized by IR and ¹H NMR spectra and size exclusion chromatography. Polarizing optical microscopy (POM) and X-ray diffraction (XRD) studies revealed that these polymers exhibited smectic A (SmA) phases. POM showed that the homopolymer showed a higher order SmA phase than did the block copolymer and copolymer. After magnetically forced alignment the samples exhibited similar optical texture but the domain size of the liquid crystalline phase increased. Differential scanning calorimetry, POM and XRD data suggest that the SmA domain size decreased in the order hompolymer > block copolymer > copolymer.     

Wide‐Ranging Host Capability of a PdII‐Linked M2L4 Molecular Capsule with an Anthracene Shell

This article reports that an M₂L₄ molecular capsule is capable of encapsulating various neutral molecules in quantitative yields. The capsule was obtained as a single product by mixing a small number of components; two Pd^II ions and four bent bispyridine ligands containing two anthracene panels. Detailed studies of the host capability of the Pd^II‐linked capsule revealed that spherical (e.g., paracyclophane, adamantanes, and fullerene C₆₀), planar (e.g., pyrenes and triphenylene), and bowl‐shaped molecules (e.g., corannulene) were encapsulated in the large spherical cavity, giving rise to 1:1 and 1:2 host–guest complexes, respectively. The volume of the encapsulated guest molecules ranged from 190 to 490 ų. Within the capsule, the planar guests adopt a stacked‐dimer structure and the bowl‐shaped guests formed an unprecedented concave‐to‐concave capsular structure, which are fully shielded by the anthracene shell. Competitive binding experiments of the capsule with a set of the planar guests established a preferential binding series for pyrenes≈phenanthrene>triphenylene. Furthermore, the capsule showed the selective formation of an unusual ternary complex in the case of triphenylene and corannulene.     

Complexation Thermodynamics of p-tert-Butylcalix[4]arene Derivatives with Light Lanthanoid Nitrates in Acetonitrile

Abstract

Calorimetric titrations have been performed for the first time in anhydrous acetonitrile at 25°C to give the complex stability constant (K _S) and thermodynamic quantities for the complexation of light lanthanoid(III) nitrates (La-Gd) with 5,11,17,23-tetra-tert-butyl-26,28-bis(cyanomethoxy)-25,27-dihydroxy-calix[4]arene (1) and 5,11,17,23-tetra-tert-butyl-26, 28-bis(2-aminoethoxy)-25,27-dihydroxycalix[4]arene (2). X-ray crystallographic structures of 1 and 2 were also determined and compared. Possessing the cyanomethoxy and aminoethyl substituents, 1 and 2 displayed strikingly different cation binding abilities and selectivity profiles with much higher K _S values for La³⁺ and Ce³⁺, which may be related to the original structures in the solid state. Thus, the binding profile for 2 showed a rapid decrease in K _S with decreasing ionic diameter from La³⁺ to Pr³⁺ and then became flat up to Gd³⁺, while 1 gave a very flat profile which is superimposable with that for 2 between Pr³⁺-Gd³⁺. Thermodynamically, the complexation is driven absolutely by enthalpy which compensates the entropic loss arising from the structural freezing of the calix[4]arene derivatives upon simultaneous binding of lanthanoid ion by the phenolic oxygen and acetonitrile molecule in the cavity. The general validity and the meaning of the compensative enthalpy-entropy relationship observed are discussed.     

Pyrene bichromophores composed of polyaminopolycarboxylate interlink: pH response of excimer emission

Fluorescent response to pH has been studied on water-soluble pyrene-based bichromophores, (edtapy)H₂ and (dtpapy)H₃, in which two pyrenyl groups are linked by an ethylenediaminetetraacetate (EDTA) and a diethylenetriaminepentaacetate (DTPA) unit, respectively, through amide linkages. The excimer emission of the EDTA derivative is strengthened sharply with increasing pH at two steps; the first step is associated with the dissociation of acidic hydrogen from amino nitrogen in partially protonated species (edtapy)H^?  and the second step is attributable to the amide group. The excitation spectra have evidenced the formation of a static excimer in the ground state of completely deprotonated species (edtapy)^2 ? . The close contact between pyrenyl groups in (edtapy)^2 ?  has been confirmed by density functional theory, which has also shown that the close contact is broken when amino nitrogen is protonated. The DTPA derivative exhibits a strong excimer emission, which shows an intensity–pH profile of an ‘off–on–off–on’ type. This rare pH response is ascribable to multiple protonation sites in the DTPA chain, as confirmed by ¹H NMR. The novel pH-sensing capabilities in specific pH regions are due to the combination of the fluorescent group with the polyaminopolycarboxylate chains whose conformations are reversibly altered by protonation–deprotonation processes.     

Preparation and Properties of Novel Cyclophosphazenes Containing Cyanato Groups

Abstract

Novel cyclotriphosphazenes containing cyanato group (PZCN) derivatives were synthesized by a substitution reaction of 4-hydroxyphenoxycyclotriphosphazenes and cyanogen bromide (BrCN) in the presence of triethylamine (TEA). The PZCNs were characterized by FT-IR, liquid chromatography–mass spectrometry (LC-MS), ¹H NMR, ¹³C NMR, and ³¹P NMR spectroscopy. Curing reactions of the PZCNs were evaluated by FT-IR spectroscopy, thermogravimetry/differential thermal analysis (TG/DTA), and differential scanning, calorimetry (DSC). The PZCNs exhibited an exothermic peak due to curing within the temperature range of 140–300°C by DSC. The PZCNs were completely cured at 220°C. The cured PZCNs exhibited high thermal stability up to 350°C, a high char-forming capability, and electrical properties, such as dielectric constants (Dks) between 2.68 and 2.87, and dissipation factors (Dfs) between 0.008 and 0.013 at 1 MHz.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Synthesis of End-Reactive Polymers with Controlled Molecular Weight by Metalloporphyrin Catalyst

α, β, γ δ-Tetraphenylporphinatoaluminum carboxylate (TPPA10COR) and phenoxide (TPPA10Ar) bring about the polymerization of β-lactone and epoxide to give polymers with controlled chain length having a carboxylic ester or phenoxy group at the end of each polymer molecule. Acrylate (TPPA10COCH=CH2) and p-vinylphenoxide (TPPA1-OC₆H₄,CH[dbnd]CH₂ (p)) as initiator give polyester or polyether macromer with narrow molecular weight distribution.