Effect of Phenolic Compounds from Cymbopogon citratus (DC) Stapf. Leaves on Micellar Solubility of Cholesterol

Dyslipidemias are one of the risk factors for cardiovascular diseases, the leading cause of death and hospitalization worldwide. One way to control cholesterol levels is to control the exogenous cholesterol intake in the body. Natural polyphenolic compounds, namely theaflavins from plant extracts such as black tea, showed the ability to inhibit the formation of the micellar structure, essential for the absorption of cholesterol in the intestine. There are several methodologies to determine this effect, many of which are expensive and time-consuming. Due to these facts, the main purposes of this work were to optimize an inexpensive colorimetric method to study, in vitro, the micellar solubility of cholesterol and applied it to plant extracts. In this work, Cymbopogon citratus leaf extracts, its phenolic fractions, and flavonoids were evaluated. The non-delipidified infusion (CcI) obtained a maximum percentage of micelle destruction of 59.22% for a concentration of 50 μg/mL and the delipidified infusion (CcdI) obtained a maximum percentage of micelle destruction of 58.01% for a concentration of 200 μg/mL. In the case of the fraction of phenolic acids (CcPAs), 23.85% of maximum micellar destruction was recorded for the concentration of 100 μg/mL, while for the fraction of flavonoids (CcF), the micellar destruction was 92.74% at 1 μg/mL, and for the tannin fraction (CcT) of 99.45% at 25 μg/mL. Luteolin presented a percentage of micelle destruction of 94.83% in the concentration of 1 ng/mL, followed by luteolin-7-O-glucoside with 93.71% and luteo-lin-6-C-glucoside with 91.26% at the concentrations of 25 ng/mL and 50 ng/mL, respectively. These results suggest the capability of polyphenols from Cymbopogon citratus to prevent the cholesterol absorption in the gut by micellar destruction, and its contribution for cholesterol-lowering activity.     

Soluble and polymer-supported 2- and 3-benzylated furans for the preparation of α,β-ethylenic carbonyl compounds

Soluble and polymer-supported 2- and 3-benzylated furans were subjected to a sequence involving a Diels-Alder reaction with α,β-acetylenic carbonyl compounds, a Michael addition, and a subsequent retro-Diels-Alder reaction to yield olefinic compounds. On solid support, this traceless strategy is advantageous since pure compounds were released in the thermal cycloreversion step. The fur-2-ylated resin allowed a highly diastereoselective synthesis.     

Stereocontrolled reduction of chiral pyrrolidine and piperidine β-enamino esters: formal enantioselective synthesis of (+)-calvine

The results of a study dealing with the chemio- and diastereoselective reduction of chiral pyrrolidine and piperidine β-enamino esters 1, 2 and 3, 4 into β-amino esters are reported. This approach was successfully applied to a formal synthesis of (+)-calvine.     

Different adsorption behaviors of methane and carbon dioxide in the isotypic nanoporous metal terephthalates MIL-53 and MIL-47

A distinct step in the isotherm occurs during the adsorption of CO2 on MIL-53 at 304 K. Such behavior is neither observed during the adsorption of CH4 on MIL-53 nor during the adsorption on the isostructural MIL-47. This phenomenon seems to be due to a different mechanism than that of previous adsorption steps on MOF samples. It is suggested that a breathing behavior is induced in MIL-53 during CO2 adsorption.     

Electrospray ionization mass spectrometry of organic-inorganic materials: identification and gas-phase reactivity of functionalized octahedral rhenium(III) clusters

Electrospray ionization mass spectrometry was used for the analysis of functionalized rhenium clusters such as [Re6Se8(o-Me2TTFPPh2)6]2+ (1), {Re6Se8[(o-Me2TTF)2PPh]6}2+ (2) and [Re6Se8(MePPh2)6]2+ (3). The high-resolution mass spectra of the intact clusters, performed in dichloromethane, confirm the identification of the compounds by comparison with the theoretical isotopic distributions. Low-resolution full-scan mass spectra recorded at increasing desolvation cone voltage values allow the study of the intrinsic reactivity of ionic species. The survival yield curves illustrating the bimolecular reactivity of 1 and 2 suggest that a bisdimethyltetrathiafulvalene(phenyl)phosphine ligand increases the stability of the functionalized ML6(2+) cluster 2. In the case of the 3, instead of loss of a neutral ligand, ligand exchange is observed either with traces of water present in dichloromethane or with acetonitrile used as solvent.     

X-ray crystallographic structure of the 9,10-dihydro-11,12bis[(1,3,3-trimethylureido)methyl]-9,10ethanoanthracene dihydrate

As a part of studies on MDR reversal agents, structure of the 9,10-dihydro-11,12-bis[(1,3,3-trimethylureido)methyl]-9,10-ethanoanthracene dihydrate is reported. Crystal data: C₂₆H₃₄N₄O₂ × 2 H₂O; mol. mass 470.60; monoclinic; space group: C2/c, a = 15.7492(6) Å; b = 7.2245(3) Å; c = 24.3442(10) Å; β = 106.795(2)^∘; V = 2651.73(22) ų; z = 4; dx = 1.179 mg/m³; μ = 0.64 mm⁻¹; F(000) = 1016; final R = 0.061 for 2501 reflections [I > 4 σ (I)]. Only half of the molecule is unique. The two nonplanar rings from the independent part of 9,10-dihydro-9,10-ethanoanthracene adopt a boat conformation. Crystallographic data demonstrate the “syn-syn” conformation of urea substituents in the molecule. In the crystal, water molecules are linked to the main species by H-bonds: O3′⋅sH12w—O1—H11w⋅sO3′(1.5 − x, 0.5 − y, 1 − z).     

Universality of local eigenvalue statistics for some sample covariance matrices

We consider random, complex sample covariance matrices X*X, where X is a p × N random matrix with i.i.d. entries of distribution μ. It has been conjectured that both the distribution of the distance between nearest neighbor eigenvalues in the bulk and that of the smallest eigenvalues become, in the limit N → ∞, → 1, the same as that identified for a complex Gaussian distribution μ. We prove these conjectures for a certain class of probability distributions μ. © 2004 Wiley Periodicals, Inc.