Crystal structure and theoretical calculations of Julocrotine,a natural product with antileishmanial activity

Julocrotine, N‐(2,6‐dioxo‐1‐phenethyl‐piperidin‐3‐yl)‐2‐methyl‐butyramide, is a potent antiproliferative agent against the promastigote and amastigote forms of Leishmania amazonensis (L.). In this work, the crystal structure of Julocrotine was solved by X‐ray diffraction, and its geometrical parameters were compared with theoretical calculations at the B3LYP and HF level of theory. IR and NMR spectra also have been obtained and compared with theoretical calculations. IR absorptions calculated with the B3LYP level of theory employed together with the 6‐311G+(d,p) basis set, are close to those observed experimentally. Theoretical NMR calculations show little deviation from experimental results. The results show that the theory is in accordance with the experimental data. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

Synthesis of new chiral imidazolium salts derived from amino acids: their evaluation in chiral molecular recognition

A family of new imidazolium salts derived from natural amino acids has been synthesized and tested for NMR enantiodiscrimination, as chiral shift reagents, of carboxylic acids. These imidazolium receptors contain different structural modifications and the splitting of the signals of the acids, after addition of the corresponding CSRs, depends on these structural variables. Compound 8b exhibited the strongest chiral solvating properties for racemic Mosher acid and was recognized as a suitable CSR for the determination of its enantiomeric composition.     

Effects of the attractive interactions in the thermodynamic, dynamic, and structural anomalies of a two length scale potential

Using molecular dynamic simulations, we study a system of particles interacting through a continuous core-softened potentials consisting of a hard core, a shoulder at closest distances, and an attractive well at further distance. We obtain the pressure-temperature phase diagram of this system for various depths of the tunable attractive well. Since this is a two length scale potential, density, diffusion, and structural anomalies are expected. We show that the effect of increasing the attractive interaction between the molecules is to shrink the region in pressure in which the density and the diffusion anomalies are present. If the attractive forces are too strong, particle will be predominantly in one of the two length scales and no density of diffusion anomaly is observed. The structural anomalous region is present for all the cases.     

Are pterins able to modulate oxidative stress?

Pterins (also known as pteridines) are common animal colorants that constitute heterocyclic compounds and have the highest nitrogen content of any pigment analyzed from animals. It has been reported that pterins modulate oxidative stress as these molecules are able to scavenge free radicals. Previous reports suggest three possible mechanisms that are responsible for scavenging free radicals; these are electron transfer (ET) reaction, hydrogen atom transfer (HAT) and radical addition. In this paper, the facility to scavenge free radicals (antiradical power) of pterins is analyzed, using density functional theory calculations and considering two possible mechanisms: ET and HAT. For the electron transfer process, considering the electron donor facility of the free radical scavenger molecules, vertical ionization energy of pterins indicates that the antiradical power of those pterins is lower than the antiradical power of any carotenoids (except for tetrahydrobiopterin). In terms of the HAT mechanism, the bond dissociation energy involved in the removal of one hydrogen atom from pterins is higher than for carotenoids (except for sepiapterin and 7,8-dihydrobiopterin). It can be expected that the most reactive molecules are those that have the smallest dissociation energy since the dissociation of the hydrogen atom is the first step of the reaction. This could indicate that some pterins are depicted as poorer antiradicals than carotenoids in terms of the HAT mechanism. Further studies focusing on the third mechanism (radical addition) and the kinetics of the reactions are necessary in order to fully understand the antiradical power of these substances. For this reason, work continues in order to clarify these aspects.     

A Validated LC Method for the Quantitation of Cefotaxime in pH-Sensitive Nanoparticles

A sensitive and rapid routine LC method was validated for measuring cefotaxime incorporated in three different pH-sensitive nanoparticles. The drug was chromatographed on a C18 reversed-phase column; the mobile phase used was 0.05 M aqueous ammonium acetate, acetonitrile and tetrahydrofuran (87:11:2, v/v) adjusted to pH 5.5 with acetic acid. The flow rate was 1 mL min^?1 and cefotaxime was quantified at 254 nm, with a sensitivity range of 0.005 AUFS. The validated method was specific, linear (R ² ≥ 0.999), precise and accurate in a concentration range of 0.2–50.0 μg mL^?1. The method was rapid, selective and suitable for evaluation of cefotaxime in pH-sensitive Eudragit nanoparticles.     

Morphology and protein content of hepatocytes in type I diabetic rats submitted to physical exercises

The importance of physical exercise practice in the treatment of diabetes has been reported in many studies recently, but only limited data can be found regarding its benefits on liver morphology and protein content of hepatocytes. In order to assess the changes arising from the development of type I diabetes and the benefits of a training protocol, Wistar rats were divided into four groups: sedentary control (SC), trained control (TC), sedentary diabetic (SD) and trained diabetic (TD). The training protocol consisted of swimming for 60 min a day, 5 days/week, during 8 weeks. Liver samples were collected, processed and analyzed by histochemical and ultrastructural techniques. Biochemical tests were also conducted to examine the protein content and quantity of DNA in the liver. In morphological assessment, the presence of areas of cytoplasmic basophilia observed in control subjects was not visualized in sedentary diabetics. It was related to differences in the amount of mitochondria in the cytosol. The mitochondrial structure has not undergone relevant changes, and the number of rough endoplasmic reticulum cisterns was clearly inferior in sedentary diabetics, suggesting lower protein production. However, the biochemical analysis of protein content indicated no statistical differences between groups. The exercise, in turn, was not responsible for major changes in these characteristics. On the whole, the morphological damages arising from type I diabetes were noteworthy. Nevertheless, regular physical training was not responsible for significant improvements in some respects, making evident the need for combined application of a distinct form of treatment.     

Influence of hydrogen bonds on the molecular structure and conformations of two (C30H48O2) pentacyclic triterpene isomers

The structural study of two (C₃₀H₄₈O₂) pentacyclic triterpene (PCTT) isomers is presented. These terpenes, known as 30-hydroxy-lup-20(29)-en-3-one (1) and (11α)-11-hydroxy-lup-20(29)-en-3-one (2), were isolated from Maytenus imbricata Mart. Ex Reissek (Celastraceae). The molecular structure of 1 and 2 differs in the position of the hydroxyl group. Both compounds crystallize in non-centrosymmetric space groups with two molecules in the asymmetric unit. The crystal structure of 1 shows a triclinic P1 space group (a = 9.5518(1) ?, b = 9.7083(1) ?, c = 14.4696(2) ?, α = 93.832(1)°, β = 102.833(1)°, and γ = 103.307(1)°), while compound 2 crystallizes in a monoclinic P2₁ one (a = 13.4439(16) ?, b = 14.4463(14) ?, c = 13.5224(9) ? and β = 99.703(8)°). The two molecules independent by symmetry of 1 differ slightly due to the presence of static disorder in oxygen atoms. In addition, the intermolecular geometries of 1 and 2 were analysed, and in each isomer the crystal packing is stabilized by O-H…O intermolecular hydrogen bonds and van der Waals forces.     

Studies on crude oil‐water biphasic mixtures by low‐field NMR

Low‐field ¹H NMR was used in this work for the analysis of mixtures involving crude oils and water. CPMG experiments were performed to determine the transverse relaxation time (T₂) distribution curves, which were computed by the inverse Laplace transform of the echo decay data. The instrument's ability of quantifying water and petroleum in biphasic mixtures following different methodologies was tested. For mixtures between deionized water and petroleum, one achieved excellent results, with root mean squared error of cross‐validation (RMSECV) of 0.8% for a regression between the water content (wt %) and the relative area of the water peak in the T₂ distribution curve, or a standard deviation of 0.9% for the relationship between the water content and the relative water peak area, corrected by the relative hydrogen index of the crude. In the case of biphasic mixtures of Mn²⁺‐doped water and crude oils, the best result of RMSECV = 1.6% was achieved by using the raw magnetization decay data for a partial least squares regression. Copyright © 2012 John Wiley & Sons, Ltd.