Anchoring of a [Mn(salen)Cl] complex onto mesoporous carbon xerogels

Carbon xerogels were synthesized by the conventional sol-gel approach using formaldehyde and resorcinol. The wet gel was dried by two different procedures followed by carbonization, leading to mesoporous carbon xerogels with considerably different pore size distributions. The materials were subsequently oxidized with air, in order to introduce functional groups on the surface, in particular phenols, anhydrides and carbonyls. The capacity of the carbon xerogels for direct immobilization of metal complexes was tested with a manganese(III) salen complex which possesses an extended ligand pi system and two reactive hydroxyl groups on the aldehyde fragment. The manganese loadings of the various samples indicate that larger amounts of Mn(III) complex were immobilized in the oxidized carbon xerogels when compared with the parent unactivated materials, suggesting that complex immobilization took place preferably by covalent bond between the surface oxygen functional groups and the ligand reactive groups, rather than by pi-pi interactions. The size and shape of the carbon xerogel pores were also shown to play an important role in the final loading of the manganese(III) salen complex.     

BORAZANs: tunable fluorophores based on 2-(pyrazolyl)aniline chelates of diphenylboron

The reaction between 2-pyrazolyl-4-X-anilines, H(pzAnX), (X = para-OMe (L1), Me (L2), H (L3), Cl (L4), CO2Et (L5), CF3 (L6), CN (L7)) and triphenylboron in boiling toluene affords the respective, highly emissive N,N'-boron chelate complexes, BPh2(pzAnX) (X = para-OMe (1), Me (2), H (3), Cl (4), CO2Et (5), CF3 (6), CN (7)) in high yield. The structural, electrochemical, and photophysical properties of the new boron complexes can be fine-tuned by varying the electron-withdrawing or -donating power of the para-aniline substituent (delineated by the substituent's Hammett parameter). Those complexes with electron-withdrawing para-aniline substituents such as CO2Et (5), CF3 (6), and CN (7) have more planar chelate rings, more 'quinoidal' distortion in the aniline rings, greater chemical stability, higher oxidation potentials, and more intense (phiF = 0.81 for 7 in toluene), higher-energy (blue) fluorescent emission compared to those with electron-donating substituents. Thus, for 1 the oxidation potential is 0.53 V versus Ag/AgCl (compared to 1.12 V for 7), and the emission is tuned to the yellow-green but at an expense in terms of lower quantum yields (phiF = 0.07 for 1 in toluene) and increased chemical reactivity. Density functional calculations (B3LYP/6-31G*) on PM3 energy-minimized structures of the ligands and boron complexes reproduced experimentally observed data and trends and provided further insight into the nature of the electronic transitions.     

Seasonal and biological variations of Epidendrum mosenii: quantification of 24-methylenecycloartanol using gas chromatography

Epidendrum mosenii is a Brazilian medicinal plant, traditionally used to treat infective and dolorous processes. The present article reports a comparative study of the chemical and pharmacological aspects of different parts and seasons of this plant. The results demonstrate that 24-methylenecycloartanol (1), one of the main active principles present in this plant, is located practically in all the parts and during all seasons, but it is much more concentrated in the stems when collected in spring and summer. The pharmacological results indicate that dichloromethane extracts collected in spring and summer were the most active when evaluated against the writhing test in mice, being several times more potent than some reference drugs used as comparison. Together, the results strongly suggest that the antinociceptive effect of E. mosenii is related, at least in part, to the presence of compound 1, and this finding could be useful for quality control of phytopreparations based on this plant.     

Mixed unsymmetric oxadiazoline and/or imine platinum(II) complexes

Iminoacylation of acetone oxime Me(2)C[double bond, length as m-dash]NOH upon reaction with trans-[PtCl(2)(NCCH(2)CO(2)Me)(2)] and [2 + 3] cycloaddition of acyclic nitrone (-)O(+)N(Me) = C(H)(C(6)H(4)Me-4) to a nitrile ligand in lead to the formation of mono-imine trans-[PtCl(2)(imine-a)(NCCH(2)CO(2)Me)] [imine-a = NH[double bond, length as m-dash]C(CH(2)CO(2)Me)ON = CMe(2)] and mono-oxadiazoline trans-[PtCl(2)(oxadiazoline-a)(NCCH(2)CO(2)Me)] [oxadiazoline-a = [upper bond 1 start]N[double bond, length as m-dash]C(CH(2)CO(2)Me)ON(Me)C[upper bond 1 end](H)(C(6)H(4)Me-4)] unsymmetric mixed ligand complexes, respectively, as the main products. Reactions of or with acetone oxime , cyclic nitrone (-)O(+)N = CHCH(2)CH(2)C[upper bond 1 end]Me(2) or N,N-diethylhydroxylamine give access, in moderate to good yields, to the unsymmetric mixed ligand oxadiazoline and/or imine complexes trans-[PtCl(2)(oxadiazoline-a)(imine-a)] , trans-[PtCl(2)(oxadiazoline-a)(oxadiazoline-b)] [oxadiazoline-b = [upper bond 1 start]N[double bond, length as m-dash]C(CH(2)CO(2)Me)O[lower bond 1 start]NC[upper bond 1 end](H)CH(2)CH(2)C[lower bond 1 end]Me(2)], trans-[PtCl(2)(imine-a)(imine-b)] [imine-b = NH = C(CH(2)CO(2)Me)ONEt(2)] or trans-[PtCl(2)(imine-a)(oxadiazoline-b)] . The cis mono-imine mixed ligand complex cis-[PtCl(2)(imine-a)(NCCH(2)CO(2)Me)] is the major product from the reaction of cis-[PtCl(2)(NCCH(2)CO(2)Me)(2)] with the oxime , while the di-imine compound cis-[PtCl(2)(imine-a)(2)] is a minor product. Reaction of cis-[PtCl(2)(imine-a)(NCCH(2)CO(2)Me)] with N,N-diethylhydroxylamine or the cyclic nitrone affords, in good yields, the unsymmetric mixed ligand complexes cis-[PtCl(2)(imine-a)(imine-b)] or cis-[PtCl(2)(imine-a)(oxadiazoline-b)] , respectively. All these complexes were characterized by elemental analyses, IR and (1)H, (13)C and (195)Pt NMR spectroscopies, and FAB(+)-MS. The X-ray structural analysis of trans-[PtCl(2){NH=C(CH(2)CO(2)Me)ON=CMe(2)}(NCCH(2)CO(2)Me)] is also reported.     

Experimental and computational study of the thermochemistry of the fluoromethylaniline isomers

The standard (po = 0.1 MPa) molar enthalpies of formation in the condensed phase of seven isomers of fluoromethylaniline were derived from the standard molar energies of combustion, in oxygen, to yield CO2(g), N2(g) and HF.10H2O(l), at T = 298.15 K, measured by rotating bomb combustion calorimetry. The standard molar enthalpies of vaporization or sublimation of these compounds, also at T = 298.15 K, were determined using Calvet microcalorimetry, while the enthalpies of fusion of the solid compounds were determined by differential scanning calorimetry. The standard molar enthalpies of formation in the gaseous phase, at T = 298.15 K, were derived from the former two experimental quantities. G3MP2//B3LYP calculations were performed for all possible fluoromethylanilines allowing the estimation of data for the isomers that were not studied experimentally. The Cox scheme was applied with two different approaches for the estimation of the standard molar enthalpies of formation of all the isomers studied, and this led to the conclusion that the literature values for the enthalpies of formation of the meta and para isomers of methylaniline seem to be not reliable. Further G3MP2//B3LYPs calculations on the methylaniline isomers yielded new values for the standard molar enthalpies of formation of the isomers of methylaniline, which have been tested under the Cox scheme, resulting in better estimates.     

Photoinduced electron transfer between the cationic complexes Ru(NH3)5pz2+ and trans-RuCl([15]aneN4)NO2+ mediated by phosphate ion: visible light generation of nitric oxide for biological targets

The photochemical behavior of the tetraazamacrocyclic complex trans-RuCl([15]ane)(NO)2+ (RuNO2+) in a 10 mM phosphate buffer solution, pH 7.4, and in the presence of Ru(NH3)5pz2+ (Rupz2+) is reported. Irradiation (436 nm) of an aqueous solution containing both cationic complexes as PF6- salts labilizes NO from RuNO2+ with a quantum yield (phiNO) dependent on the concentration of Rupz2+ with a maximum value of phiNO (1.03(11)x10(-3) einstein mol-1) found for a solution with equimolar concentrations (5x10(-5) M) of the two complexes in phosphate buffer solution. The quantitative behavior of this system suggests that the two cations undergo preassociation such that photoexcitation of the visible absorbing Rupz2+ is followed by electron or energy transfer to RuNO2+, which does not absorb appreciably at the excitation wavelength, and this leads to NO release from the reduced nitrosyl complex. Notably, the NO release was not seen in the absence of phosphate buffer; thus, it appears that phosphate ions mediate NO generation, perhaps by facilitating formation of a supramolecular complex between the two ruthenium cations. Reexamination of the cyclic voltammetry of Rupz2+ showed that the electrochemical behavior of this species is also affected by the presence of the phosphate buffer.     

Immobilization of hexokinase onto chitosan decorated particles

Chitosan (CH) decorated polystyrene (PS) particles were synthesized within complexes of CH, a polycation under acid conditions, and tiny amounts of sodium dodecylsulfate (SDS). Particle characterization was performed by means of dynamic light scattering, zeta potential measurements, and transmission electron microscopy. All dispersions were stable in the ionic strength of 2.0 mol L-1 NaCl during 2 months. The outstanding colloidal stability was attributed to the presence of a hydrated CH layer around the particles. CH decorated PS particles were attached to atomic force microscopy cantilevers and probed against Si wafers in water and in NaCl 0.01 mol/L. The mean thickness of CH layer amounted to 35 +/- 11 and 16 +/- 6 nm, when the medium was water and NaCl 0.01 mol/L, respectively. Adsorption isotherm of hexokinase (HK) onto PS/CH particles studied by means of spectrophotometry showed three regions: an initial step; adsorption plateau and multilayer formation. Enzymatic activity of free HK and immobilized HK was monitored by means of spectrophotometry as a function of storing time and reuse. After 3 days, storing HK free in solution dramatically lost its catalytic properties. On the contrary, HK-covered PS/CH particles retained enzymatic activity over 1 month. Moreover, HK-covered PS/CH particles could be reused in the determination of glucose two times consecutively, without losing activity. These interesting findings were discussed in light of the role of water in enzyme conformation.     

Molecular dynamics study of ethanolamine as a pure liquid and in aqueous solution

Molecular dynamics simulations have been carried out for ethanolamine as a pure liquid and in aqueous solution at 298 and 333 K. The ethanolamine force field has been parametrized to reproduce intramolecular energies from quantum mechanical calculations and experimentally determined properties of the liquid. The results are presented for conformer distributions, density, enthalpy of vaporization, self-diffusion constant, dielectric constant, and radial distribution functions. The results strongly suggest that the main (O-C-C-N) dihedral tends to stay in its gauche conformers in solution and that the ethanolamine molecules populate conformers with a significant degree of intramolecular hydrogen bonding. This result is also supported by results from a continuum solvation model. Simulation of a 10 mol % aqueous ethanolamine system suggests that ethanolamine is preferentially solvated to by water molecules. The results suggest that ethanolamine dimer formation in aqueous solution is very limited. Simulations were also carried out for CO2 in an aqueous ethanolamine system. The results suggest that CO2 has a comparable level of attraction to ethanolamine and water. The degree of interaction between CO2 and the amine and alcohol functionalities in ethanolamine also appear to be of comparable strength.     

Pharmacological and Therapeutic Potential of Myristicin: A Literature Review

Natural products have been used by humanity for many centuries to treat various illnesses and with the advancement of technology, it became possible to isolate the substances responsible for the beneficial effects of these products, as well as to understand their mechanisms. In this context, myristicin, a substance of natural origin, has shown several promising activities in a large number of in vitro and in vivo studies carried out. This molecule is found in plants such as nutmeg, parsley, carrots, peppers, and several species endemic to the Asian continent. The purpose of this review article is to discuss data published in the last 10 years at Pubmed, Lilacs and Scielo databases, reporting beneficial effects, toxicity and promising data of myristicin for its future use in medicine. From 94 articles found in the literature, 68 were included. Exclusion criteria took into account articles whose tested extracts did not have myristicin as one of the major compounds.     

Development and Validation of QuEChERS Followed by UHPLC-ToF-MS Method for Determination of Multi-Mycotoxins in Pistachio Nuts

Pistachios are one of the types of tree nut fruits with the highest mycotoxin contamination, especially of aflatoxins, worldwide. This study developed a Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) method that was followed by Ultra-High Performance Liquid Chromatography combined with Time-of-Flight Mass Spectrometry (UHPLC–ToF-MS) for the determination of mycotoxins in pistachios. Different approaches to dispersive solid phase extraction as a clean-up method for high lipid matrices were evaluated. For this, classic sorbents such as C18 (octadecyl-modified silica) and PSA (primary secondary amine), and new classes of sorbents, namely EMR-Lipid (enhanced matrix removal-lipid) and Z-Sep (modified silica gel with zirconium oxide), were used. The QuEChERS method, followed by Z-Sep d-SPE clean-up, provided the best analytical performance for aflatoxins (AFB1, AFB2, AFG1 and AFG2), ochratoxin A (OTA), zearalenone (ZEA), toxin T2 (T2) and toxin HT-2 (HT2) in pistachios. The method was validated in terms of linearity, sensitivity, repeatability, interday precision and recovery; it achieved good results according to criteria imposed by Commission Regulation (EC) no. 401/2006. The method was applied to real samples and the results show that pistachios that are available in Portuguese markets are safe from mycotoxins that are of concern to human health.