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1.
Ren Y Acuña UM Jiménez F García R Mejía M Chai H Gallucci JC Farnsworth NR Soejarto DD Carcache de Blanco EJ Kinghorn AD 《Tetrahedron》2012,68(12):2671-2678
Six new (1-6) and eight known germacranolide-type sesquiterpene lactones, along with several known phenylpropanol coumarates and methylated flavonoids, were isolated from the leaves of Piptocoma rufescens, collected in the Dominican Republic. The new compounds were identified by analysis of their spectroscopic data, with the molecular structure of 3 being established by single-crystal X-ray diffraction. The absolute configurations of the sesquiterpene lactones isolated were determined from their CD and NOESY NMR spectra, together with the analysis of Mosher ester reactions. Bioassay screening results showed the majority of the sesquiterpene lactones isolated (1-13) to be highly cytotoxic toward the HT-29 human colon cancer cell line, with the most potent compound being 15-deoxygoyazensolide (10, IC(50), 0.26 μM). In addition, several of the sesquiterpene lactones exhibited NF-κB (p65) inhibitory activity. 相似文献
2.
A simple analytical scheme for the detection and quantification of amitrol and triazine herbicides (atrazine, ametryn and atraton) and degradation product (2‐hydroxyatrazine) in environmental water samples by CZE is reported. On‐column preconcentration of analytes from untreated water samples (mineral, spring, tap and river water) is accomplished by introducing an acid plug (200 mM citrate of pH 2.0) after the sample and then proceeding with the CZE separation, using 100 mM formiate buffer of pH 3.5 as running buffer and 25.0 KV as separation voltage. UV detection at 200 nm provides LODs from 50 to 300 nM in untreated samples and they were lowered tenfold by sample preconcentration by evaporation. Calculated recoveries were typically higher than 90%. Minimal detectable concentration of the electroactive amitrol could be decreased about 20‐fold when electrochemical detection was employed by monitoring the amperometric signal at +800 mV using a carbon paste electrode (LOD of 9.6 nM, 0.81 μg/L, versus 170 nM, 14.3 μg/L, using amperometric and UV detection, respectively) in untreated water samples. 相似文献
3.
M.Victoria Mart?&#x;nez-D?&#x;azSagrario Esperanza Andrés de la EscosuraMarinella Catellani Sami YunusSilvia Luzzati Tomás Torres 《Tetrahedron letters》2003,44(46):8475-8478
Two new donor-acceptor copolymers comprising a polythiophene backbone, and bearing phthalocyanine chromophores on the side chains have been prepared. Preliminary photophysical characterization of these materials by FTIR photoinduced absorption indicates that electron transfer from the polythiophene to the phthalocyanine units takes place. 相似文献
4.
Severo Vázquez-Prieto Esperanza Paniagua Hugo Solana Florencio M. Ubeira Humberto González-Díaz 《Molecular diversity》2017,21(3):713-718
In the last years, the encryption of system structure information with different network topological indices has been a very active field of research. In the present study, we assembled for the first time a complex network using data obtained from the Immune Epitope Database for fungi species, and we then considered the general topology, the node degree distribution, and the local structure of this network. We also calculated eight node centrality measures for the observed network and compared it with three theoretical models. In view of the results obtained, we may expect that the present approach can become a valuable tool to explore the complexity of this database, as well as for the storage, manipulation, comparison, and retrieval of information contained therein. 相似文献
5.
Sáiz J Bravo JC Velasco Ávila E Torre M García-Ruiz C 《Journal of separation science》2011,34(23):3353-3358
In this study, a sequential extraction method using water and methanol to recover ethylene glycol dinitrate or nitroglycol (EGDN) contained in Goma-2 ECO dynamite was developed. After, an HPLC method was used for the determination of EGDN in the two extracted phases. The analytical method was validated by evaluating its selectivity, sensitivity, linearity, and linear working concentration range, limit of detection and quantitation, precision (as repeatability and intermediate precision), accuracy, and robustness, providing appropriate values (i.e. RSD values for precision about 6% and accuracy about 100%). Finally, the EGDN content of a sample of the Goma-2-ECO dynamite was determined obtaining a concentration of 30.29%, which is in accordance with the manufacturer's specifications for this dynamite (25.7-31.4%). 相似文献
6.
Rubén A. Machado David Rivillo Lindora D’Ornelas Reinaldo Atencio Esperanza Galarza 《Journal of organometallic chemistry》2004,689(15):2486-2493
The reaction of the labile compound [Re2(CO)8(CH3CN)2] with trans-1,2-bis(2-pyridyl)ethene (C12H10N2) at room temperature in tetrahydrofuran affords the compounds [Re2(μ:η3-C12H10N2)(CO)8] (1) and the oxidative addition product [Re2(μ-H)(μ:η3-C12H9N2)(CO)7] (2). When the reaction is carried out at temperatures of refluxing tetrahydrofuran, besides compounds 1 and 2, the oxidative addition product [Re2(μ-H)(μ:η4-C12H9N2)(CO)6] (3), the insertion product [Re2(μ:η4-C12H10N2)(CO)8] (4) and [Re2(μ:η6-C24H18N4)(CO)6] (5) are obtained. Compound 5 contains the organic ligand rtct-tetrakis(2-pyridyl)cyclobutandiyl which is derived from a [2 + 2] cycloaddition of 1,2-bis(2-pyridyl)ethene mediated by its coordination to the bimetallic framework. The molecular structures of 1, 2, 4 and 5 were confirmed by X-ray crystallographic studies. 相似文献
7.
A chlorinated side product was formed under Overman rearrangement conditions from a trichloroacetimidate along with the expected allylic amide. The chlorinated product derived from a hex-2-enopyranoside was obtained in a totally stereoselective manner, and it can be a useful synthetic intermediate for chlorinated sugars. In order to improve the isolated yields of either the expected Overman rearrangement product or the chlorinated compound, we carried out a thorough study on the experimental conditions. The application of the latter for the synthesis of potential calpain inhibitors is also reported. 相似文献
8.
Eliete Marçal Guimarães Raso Maria Esperanza Cortes Karina Imaculada Teixeira Milton Batista Franco Nelcy Della Santina Mohallem Ruben Dario Sinisterra 《Journal of inclusion phenomena and macrocyclic chemistry》2010,67(1-2):159-168
The purpose of this study was to prepare and characterize a controlled release system based on porous silica loaded with chlorhexidine (Cx) and its inclusion compounds in β-cyclodextrin (βcd), and to evaluate its antimicrobial activity. Acetate chlorhexidine (CxA), gluconate chlorhexidine (CxG), βcd:chlorhexidine acetate 2:1 (βcd:CxA) and βcd:chlorhexidine gluconate 2:1 (βcd:CxG) were incorporated into porous silica. Drug loading was characterized by FTIR, powder X-ray diffraction, thermal analysis and BET, and was shown to be in an amorphous state and porous matrix. The kinetics release parameter of the drug was established, which showed that the Cx systems release profile followed zero order release until 400 h and Higuchi model release until 750 h, after the burst effect at the first 8 h. Chlorhexidine therapeutic range was reached near first hour for all systems. The chlorhexidine porous silica system was biologically active against Enterococcus faecalis and Candida albicans in vitro. The systems showed an efficient Cx controlled release modulated by the presence of the β-cyclodextrin and by the porous silica matrices, providing effective antimicrobial activity. 相似文献
9.
Esperanza Menéndez Luis Vega Carmen Andrade 《Journal of Thermal Analysis and Calorimetry》2012,110(1):203-209
In field structures affected by fire, the temperature progress through the material. The progression of temperature in the concrete material can be determined by simultaneous differential thermal analysis and thermogravimetry. Also, the analysis of the behaviour of concrete in real concrete, by different techniques, permits the corroboration of the hypothesis of cover calculation. In this study, the analysis of concrete exposed to a very severe fire is studied in order to corroborate the calculus hypothesis and to determine the progression of the temperature inside the affected structure. In this study, the potentiality of the thermal instrumental techniques is studied to determine the situation of the concrete exposed to fire. These results can be used to calculate the residual strength of the concrete structural elements. Also, other auxiliary techniques are used to have some supplementary information about the situation of the concrete exposed to fire. The results are based in concrete samples from a real fire in the Windsor Building in Madrid. The Windsor Building in Madrid was project in 1974 and built between 1975 and 1979. This building was severely damaged by a serious fire on the 12th of February 2005, which lasted approximately 12?h. 相似文献
10.
Esperanza Salfrn Carlos Seoaneb Margarita Surez Yamila Verdecia Amaury Alvarez Estael Ochoa Roberto Martínez‐Alvarez Nazario Martín 《Journal of heterocyclic chemistry》2004,41(4):509-516
Novel 4‐amino‐6‐aryl‐2‐phenylpyrimidine‐5‐carbonitriles have been prepared in one step procedure from the readily available 4‐aryl‐2‐amino‐3‐cyano‐5,6,7,8‐tetrahydro‐7,7‐dimethyl‐5‐oxo‐4H‐benzopyrans. The mass spectroscopy study under EI conditions shows molecular peaks with high intensity corresponding to the loss of benzonitrile from the C2 position of the pyrimidine ring. Semiempirical (AMI and PM3) and ab initio HF/6–31G* calculations reveal a favored distorted geometry where the three rings are not in the same plane. 相似文献