Inclusion complexes with cyclodextrin and usnic acid

Molecular inclusion complexes of usnic acid (UA) with β-cyclodextrin (β-CD) and 2-hydroxypropyl β-cyclodextrin (HP β-CD) were prepared by the co-precipitation method in the solid state in the molar ratio of 1:1. Structural complexes characterization was based on different methods, FTIR, ¹H NMR, XRD and DSC. Parallel to the complex by the above methods, corresponding physical mixtures of UA with cyclodextrins and complexing agents (β-CD, HP β-CD and UA) were analyzed. The results of DSC analysis showed that, at around 200 °C, the endothermal peak in the complexes with cyclodextrins originating from the UA melting has disappeared. Complex diffractogram patterns do not contain peaks characteristic for the pure UA. They are more appropriate to cyclodextrin diffractogram. This fact points to the molecular encapsulation of UA in the cyclodextrin cavity. Chemical shifts in ¹H NMR spectra after the inclusion of UA into the cyclodextrin cavity, especially H-3 protons (0.0012 and 0.0102 ppm in the β-CD and HP β-CD, respectively) and H-5 and H-6 (0.0134 ppm) and hydrogen from CH₃ (0.0073 ppm) HP β-CD also points to the formation of molecular inclusion complexes. The improved solubility of UA in water was achieved by molecular incapsulation. In the complex with β-CD the solubility is 0.3 mg/cm³, with HP β-CD 4.2 mg/cm³ while the uncomplexed UA solubility is 0.06 mg/cm³. The microbial activity of UA and both complexes was tested against eight bacteria and two fungi and during the test no reduced activity of UA in the complexes was observed.     

Azo and azoxythiacrown ethers: synthesis and properties

A series of 16- and 18-membered azo- and azoxythiacrown ethers have been synthesized by reductive macrocyclization of the respective bis(nitrophenoxy)oxaalkanes. The aromatic residues located in the polyether region of the molecule were introduced to macrocyclic skeletons and their affinities toward different groups of metal cations in ion-selective electrodes were described. X-ray structures for one dinitropodand and one azoxybenzothiacrown exhibiting strong π–π and π–H interactions have been found.     

Synthesis of new iron–NHC complexes as catalysts for hydrosilylation reactions

A series of new piano‐stool iron(II) complexes comprising N‐heterocyclic carbene ligands [Fe(Cp)(CO)₂(NHC)]I (NHC = 1,3‐disubstituted imidazolidin‐2‐ylidene) have been synthesized and analyzed by ¹H NMR, ¹³C NMR, IR, elemental analysis and mass spectrometric techniques. These compounds were easily prepared from the reaction of disubstituted imidazolidin‐2‐ylidene with [FeI(Cp)(CO)₂] in toluene at room temperature. These complexes were tested in the catalytic hydrosilylation reaction of aldehydes and ketones with phenylsilane in solvent‐free conditions. After a basic hydrolysis step, the corresponding alcohols were obtained in good yields. Copyright © 2013 John Wiley & Sons, Ltd.     

New Nanostructured Materials: Synthesis of Dodecanuclear NiII Complexes and Surface Deposition Studies

Microwave‐assisted synthesis has been used to obtain the family of dodecanuclear Ni^II complexes [Ni₁₂(NO₃)(MeO)₁₂(MeC₆H₄CO₂)₉(MeOH)₁₀(H₂O)₂][ClO₄]₂ ( 1 ), [Ni₁₂(NO₃)(MeO)₁₂(BrC₆H₄CO₂)₉(MeOH)₁₀(H₂O)₂][ClO₄]₂ ( 2 ), [Ni₁₂(CO₃)(MeO)₁₂(MeC₆H₄CO₂)₉(MeOH)₁₀(H₂O)₂]₂[SO₄] ( 3 ) and [Ni₁₂(NO₃)(MeO)₁₂(MeC₆H₄CO₂)₉(MeOH)₈(H₂O)₇][NO₃]₂ ( 4 ). They contain three {Ni₄O₄} cubane units which template around a central μ₆ anion, either NO₃^? or CO₃^2?. Their magnetic properties have been studied by superconducting quantum interference device (SQUID) magnetometry and high‐field EPR measurements. The nanostructuration of the Ni₁₂ species on mica surfaces is studied by AFM and grazing‐incidence X‐ray diffraction, which reveal the formation of polycrystalline thin layers.     

Hibernation impact on the catalytic activities of the mitochondrial D-3-hydroxybutyrate dehydrogenase in liver and brain tissues of jerboa (<Emphasis Type="Italic">Jaculus orientalis</Emphasis>)

Background

Jerboa (Jaculus orientalis) is a deep hibernating rodent native to subdesert highlands. During hibernation, a high level of ketone bodies i.e. acetoacetate (AcAc) and D-3-hydroxybutyrate (BOH) are produced in liver, which are used in brain as energetic fuel. These compounds are bioconverted by mitochondrial D-3-hydroxybutyrate dehydrogenase (BDH) E.C. 1.1.1.30. Here we report, the function and the expression of BDH in terms of catalytic activities, kinetic parameters, levels of protein and mRNA in both tissues i.e brain and liver, in relation to the hibernating process.

Results

We found that: 1/ In euthemic jerboa the specific activity in liver is 2.4- and 6.4- fold higher than in brain, respectively for AcAc reduction and for BOH oxidation. The same differences were found in the hibernation state. 2/ In euthermic jerboa, the Michaelis constants, K_M BOH and K_M NAD⁺ are different in liver and in brain while K_M AcAc, K_M NADH and the dissociation constants, K_D NAD⁺and K_D NADH are similar. 3/ During prehibernating state, as compared to euthermic state, the liver BDH activity is reduced by half, while kinetic constants are strongly increased except K_D NAD⁺. 4/ During hibernating state, BDH activity is significantly enhanced, moreover, kinetic constants (K_M and K_D) are strongly modified as compared to the euthermic state; i.e. K_D NAD⁺ in liver and K_M AcAc in brain decrease 5 and 3 times respectively, while K_D NADH in brain strongly increases up to 5.6 fold. 5/ Both protein content and mRNA level of BDH remain unchanged during the cold adaptation process.

Conclusions

These results cumulatively explained and are consistent with the existence of two BDH enzymatic forms in the liver and the brain. The apoenzyme would be subjected to differential conformational folding depending on the hibernation state. This regulation could be a result of either post-translational modifications and/or a modification of the mitochondrial membrane state, taking into account that BDH activity is phospholipid-dependent.

     

Enantioseparation of aromatic amino acids using CEC monolith with novel chiral selector,N‐methacryloyl‐l‐histidine methyl ester

A new type of polymethacrylate‐based monolithic column with chiral stationary phase was prepared for the enantioseparation of aromatic amino acids, namely d ,l ‐phenylalanine, d ,l ‐tyrosine, and d ,l ‐tryptophan by CEC. The monolithic column was prepared by in situ polymerization of butyl methacrylate (BMA), N‐methacryloyl‐l ‐histidine methyl ester (MAH), and ethylene dimethacrylate (EDMA) in the presence of porogens. The porogen mixture included DMF and phosphate buffer. MAH was used as a chiral selector. FTIR spectrum of the polymethacrylate‐based monolith showed that MAH was incorporated into the polymeric structure via in situ polymerization. Some experimental parameters including pH, concentration of the mobile phase, and MAH concentration with regard to the chiral CEC separation were investigated. Single enantiomers and enantiomer mixtures of the amino acids were separately injected into the monolithic column. It was observed that l ‐enantiomers of aromatic amino acids migrated before d ‐enantiomers. The reversal enantiomer migration order for tryptophan was observed upon changing of pH. Using the chiral monolithic column (100 μm id and 375 μm od), the best chiral separation was performed in 35:65% ACN/phosphate buffer (pH 8.0, 10 mM) with an applied voltage of 12 kV in CEC. SEM images showed that the chiral monolithic column has a continuous polymeric skeleton and large through‐pore structure.     

Differential Pulse Voltammetric Determination of Montelukast in Tablets and Human Plasma by Using Chitosan Modified Carbon Paste Electrode

Electrochemical reduction and determination of montelukast (MKS) was studied in methanol – 0.1 M HCl solution (1 : 1, v/v) by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) at chitosan modified carbon paste electrode. The linear range was 1.70×10^?7–1.83×10^?5 M for DPV analysis. Limit of detection (LOD) and limit of quantification (LOQ) were 5.32×10^?8 M and 1.61×10^?7 M, respectively. The developed method was successfully applied to the determination of MKS in tablets and spiked human plasma. The results obtained were in good agreement with those obtained using a reported spectrofluorimetric technique.     

Electroanalysis of Caffeic Acid in Red Wine and Investigation of Thermodynamic Parameters Using an Ag Nanoparticles Modified Poly(Thiophene) Film Glassy Carbon Electrode

A silver nanoparticle decorated poly(thiophene) modified glassy carbon electrode (GCE) was prepared for determination of caffeic acid. The Ag/PTh/GCE surface was characterized by scanning electron microscopy (SEM) and energy‐dispersive X‐ray (EDX) spectroscopy. The modified electrode has shown higher electrocatalytic activity towards the oxidation of caffeic acid. The peak current of was found linear in the concentration range from 1.00×10^?8 to 4.83×10^?6 M with a detection limit of 5.3×10^?9 M (S/N=3). The modified electrode was used for determination of CA concentration in red wine samples. The thermodynamic constants, entropy change (ΔS), enthalpy change (ΔH) and Gibbs free energy change (ΔG) were calculated as ?166.34 J/(mol K), ?154.24 kJ/mol and ?104.75 kJ/mol at 25 °C, respectively.     

Synthesis of Two Alnustone-Like Natural Diarylheptanoids via 4 + 3 Strategy

The first total synthesis of (4E,6E)-1,7-bis(3,4-dihydroxyphenyl)-hepta-4,6-dien-3-one and an alternative synthesis of (4E,6E)-1,7-bis(4-hydroxyphenyl)-hepta-4,6-dien-3-one, two natural diarylheptanoids, mainly based on Claisen–Schmidt condensation were described. The crucial steps of the syntheses were the condensation of OH-protected 4-aryl-2-butanones with OH-protected 3-aryl-acrylaldehydes by the in situ enamination and then deprotection of OH groups to give the corresponding natural diarylheptanoids.