Results 1 - 10 of 212
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[en] Two new monocyclic naphthene derivatives (1and 2) along with seven known compounds for the first time from the chloroform soluble fraction of the Tamarix indica. The structures of the isolated compounds were elucidated on the basis of modern sophisticated, EIMS, HREIMS, 1D and 2D-NMR spectroscopic techniques. The known compounds were recognized as 1- eicosanoyl (3), 6-heneicosanyl-1,2,4-trimethoxybenzene (4), 3 hydroxybenzoic acid (5), ethyl gallate (6) gallic acid (7), β-sitosterol (8) and methyl grevillate (9). (author)
[en] A number of per-6-substituted-6-deoxy-β-cyclodextrin derivatives have been synthesized for many years, of them, per-6-deoxy-6-iodo-β-cyclodextrin is of great importance in supramolecular chemistry. By reviewing all published papers related to synthesis of per-6-deoxy-6-iodo-β-cyclodextrin and combining with our experimental verification, this work has reported an improved method of synthesis of per-6-deoxy-6-iodo-β-cyclodextrin. The approach mainly uses adding a certain amount of methanol instead of removing DMF before adjusting pH. We think this project is simple, efficient, high repeatable and suitable for large-scale preparation, superior even to all the previously reported methods. The synthesis of bromo, chloro substituted -per-6-β-CD may also refer to this improved method. At the same time, the detailed introduction of operation process and precautions will serve as a reference and guidance to the beginner who will engage in the study on the chemical synthesis reaction of sugar and cyclodextrin. (author)
[en] Almost all the elements in the periodic table have at least one natural isotope active in NMR. Although the same principles apply to all of them, accessing to the NMR information greatly depends on the properties of each nucleus. This article describes these issues as the starting point to show the breath of applications derived from the multinuclear approach of this spectroscopic technique across the periodic table based on representative selected examples in solution.
[es]Prácticamente todos los elementos de la tabla periódica tienen al menos un isótopo natural activo en RMN. Aunque todos se rigen por los mismos fundamentos, la accesibilidad de la información de RMN está condicionada por las propiedades de cada núcleo. En este artículo se analizan esos condicionantes como punto de partida para mostrar la amplitud de aplicaciones asociadas al recorrido multinuclear de esta técnica espectroscópica a través de la tabla periódica sobre la base de una selección de ejemplos representativos en disolución.
[en] (20R,24R)-epoxy-dammar-3 beta,6 alpha,12 beta,25-tetraol (1) and (20R,24S)-epoxy-dammar-3 beta, 6 alpha,12 beta,25-tetraol(2) have been synthesized from 20(R)-protopanaxatriol with same polarity. In order to obtain optically pure 1and 2, (20R,24R)-3,6-diacetyl-20,24-epoxydammar-3 beta,6 alpha,12 beta,25-tetraol (3) and (20R,24S)-3,6-diacetyl-20,24-epoxydammar-3 beta,6 alpha,12 beta, 25-tetraol (4) were designed and prepared to enhance the polarity difference of C24 epimers. Two suitable crystals of 3 and 4 were obtained and their structures were determined by 1H NMR, 13C NMR, HR-MS and X-ray single-crystal diffraction. The results indicated that the C-24 configuration of 3 and 4 are R-form and S-form, respectively. 3 has two intramolecular hydrogen bond. While there is only one in 4 and the crystal stacking displays that it generates a right-handed helically chiral channel viewing from the crystallographic b axis via classical O-H O intermolecular hydrogen bond. (author)
[en] Previously we introduced and validated the average pixel intensity (API) method for grading mitral regurgitation (MR) in a heterogeneous MR population. We now investigated the feasibility and added value of the API method more specifically in patients with functional MR (FMR). We consecutively enrolled 283 patients with pure FMR. Transthoracic echocardiography was performed and MR was assessed using the API method and guideline-recommended parameters, including color Doppler, vena contracta width (VCW) and proximal isovelocity surface area (PISA)-based methods. The API method had an applicability of 98% in this FMR cohort, which was significantly higher than VCW (84%) and PISA-based methods (75%). Overall, the API method had significant correlations with direct parameters of FMR severity, ejection fraction, atrial and ventricular dimensions, pulmonary pressures and New York Heart Association class. Analysis of the API dynamics during MR revealed a typical pattern with early and late systolic peaks in API and a midsystolic nadir, which matched the temporal changes of the effective regurgitant orifice (ERO) during FMR. Based on ROC curves of established FMR severity cut-offs, an API value of 125 au was considered the optimal cut-off to determine severe MR. Interestingly, this API severity cut-off is similar to the API severity cut-off for MR in degenerative MR (DMR), despite different EROA/RV cut-offs in current ESC guidelines for FMR and DMR. The API method is an easy, fast and feasible parameter for grading FMR and may complement the multiparametric assessment of FMR in daily clinical practice.
[en] Salvadoramide (1) have been isolated from the ethyl acetate soluble fraction of the whole plant of Salvadora oleoides. The structure, (2R)-2-hydroxy-N-[(2S, 3S, 4R, 5E, 7E)-1, 3, 4 trihydroxy-5, 7-tetra decdiene-2-yl] tetradecanamide), was established by the use of sophisticated modern spectroscopic techniques (1D and 2D-NMR, EIMS, HREIMS, UV and IR) and chemical reactions. The compound was further evaluated for its antimicrobial activity. (author)
[en] A new thorium (IV) selective receptor (S) was developed by reacting 1,10-phenanthroline-2,9-dicarbohydrazide with 2-hydroxy naphthaldehyde. The sensing ability of S towards thorium ion was investigated in solution using spectrophotometric and Red-Green-Blue (RGB) values. The selective interaction of Swas examined with thirty different metal ions. Results shows that upon interacting with S, the colorless solution S turns into yellow-orange with thorium ions while other metal ions did not respond. The receptor S exhibits two absorbance peaks appeared at 320 nm and 375 nm due to ligand-ligand charge transfer (LLCT). On interacting with thorium (IV) ions, the receptor S experience red shift of both the peaks appeared at 335 nm and 440 nm due to metal-ligand charge transfer (MLCT). The spectral studies indicate the formation of a 1:1 complex between the S and thorium (IV) with a binding constant of 4.7×103 M-1. The limit of detection (LOD) of S for the analysis of thorium (IV) using spectrophotometric and RGB values are found to be 1.2 ppb and 3 ppb respectively. Besides, S was applied for the analysis of thorium (IV) content present in various samples such as monazite and lantern mantle. The binding mechanism of S with thorium (IV) are investigated by 1H NMR, ESI-mass and theoretical studies
[en] A convenient and selective method for the preparation of substituted iodoalkynes based on the interaction of prop-2-yn-1-ol, prop-2-yn-1-yl acetate and 2-methylbut-3-yn-2-ol with iodine in the presence of readily available cadmium (II) acetate in ethanol has been developed. The procedure lasts for 5-30 min with stirring at 25°C. The diagnostic test confirming the structure of substituted iodoalkynes are the signals in the 13C NMR spectrum of the alkyne carbon atom associated with iodine. The reaction was monitored by TLC on Silufol UV-254 plates and after the completion of the reaction, the products were extracted by ether (3×10 ml), the combined ethereal extracts were washed with the solutions of 10 percent Na2S2O3 and 20 percent NaHCO3, dried over anhydrous magnesium sulfate and the ether was removed on a rotary evaporator
[en] Foods with high lipid contents are susceptible to deterioration by oxidative processes that lead to the formation of food rancid. Determining the chemical nature of lipid oxidation products presents a nutritional and health interest due to the possibility of formation of compounds related to the development of degenerative diseases such as Parkinson's and Alzheimer's. In this context, the present study describes the use of nuclear magnetic resonance (NMR) spectroscopy and principal component analysis (PCA) to monitor the formation of oxidation products in Brazilian table margarines subjected to the heat treatment at 80, 100, 120, 140, 160 and 180 ° C. Lipid profiles were characterized by 1H NMR experiments. Changes due to heat treatment were identified by NMR-PCA models, which indicated triacylglycerol (TAG) as the main descriptor from 160 °C. At this temperature, were identified signals evolution in 1H NMR spectra whose chemical shifts (δ) indicated the formation of aldehydes and dienes. The results were useful to highlight the need for efficient methods to maintain the oxidative stability of this type of food widely used in industrial and home cooking. (author)
[en] Chemical investigation of the crude PDB extract obtained from the endophytic fungus Schizophyllum commune afforded the pure substances, cyclo(L-Pro-L-Val) (1), uracil (2), cyclo(Pro-Tyr) (3), p-hydroxybenzoic acid (4) and a mixture of Rel.cyclo(Pro-Phe) (5) and Rel.cyclo(Pro-Ile) (6). When cultured in corn, the extract of this fungus yielded N-(2-phenylethyl) acetamide (7) and N-(4-hydroxyphenylethyl) acetamide (8). The structures of all compounds were determined based on the analyses of their MS, 1D and 2D-NMR spectroscopic data. Analysis of the crude extracts obtained from small-scale cultures (in PBD, YM, Nutrient, Czapek, Malt Extract, Corn and Rice) and a large-scale culture (in PDB) by mass spectrometry showed the presence of diketopiperazines 1, 3, 5 and 6. The crude extracts showed promising antioxidant, antifungal and acetylcholinesterase (AChE) inhibitory activities. The metabolites 7 and 8 showed antifungal and AChE inhibitory activities in vitro. This is the first report of the identification and isolation of diketopiperazines, arylethylamides, p-hydroxybenzoic acid in endophytic fungus of the Schizophyllum genus. (author)