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161.
Beel R Kobialka S Schmidt ML Engeser M 《Chemical communications (Cambridge, England)》2011,47(11):3293-3295
SOMO catalysis has lately obtained large interest as a new and powerful version of enantioselective organocatalysis which includes radical steps initiated by a one-electron oxidation. The intermediate enamine radical cation has been postulated, but has not been observed directly so far. This communication now reports the direct detection of this key intermediate. 相似文献
162.
Ana Rita de Mello Costa Flávia Silva Marquiafável Mirela Mara de Oliveira Lima Leite Vaz Bruno Alves Rocha Paula Carolina Pires Bueno Pedro Luiz M. Amaral Hernane da Silva Barud Andresa Ap. Berreta-Silva 《Journal of Thermal Analysis and Calorimetry》2011,104(1):273-278
Quercetin is a flavonoid very well studied and has already entered clinical trials emerging as prospective anticancer drug candidate. In addition, quercetin has being reported to its free-radical scavenging activity and suggests potential uses for the prevention and treatment of pathologies as atherosclerosis, chronic inflammation, and others. However, quercetin is sparingly soluble in water, which may be responsible for its limited absorption upon oral administration. The solid dispersion of quercetin with polyvinylpyrrolidone Kollidon® 25 (PVP K25) suggests an interesting way to increase quercetin solubility, antioxidant activity, and consequently bioavailability. Then, the purpose of this study was to prepare solid dispersions of quercetin with PVP K25 and evaluate their thermal characterization, antioxidant activity and quercetin improvement solubility. For this purpose, quercetin-PVP K25 solutions were dried and quercetin-PVP K25 solids were obtained. The formation of quercetin-PVP K25 solid dispersion was evaluated by solubility studies, powder X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), thermogravimetry (TG), and antioxidant activity. It was observed that PVP K25 was able to provide quercetin clear aqueous solutions and that quercetin solubility was increased in a PVP K25 concentration dependent manner, improving solubility even 436-fold the pure quercetin. The results obtained with XRD, FT-IR, DSC, and TG demonstrated possible quercetin-PVP K25 solid dispersion formation. Besides, the antioxidant activity of the quercetin-PVP K25 solid dispersions dissolved in aqueous solution and pure quercetin dissolved in methanol showed IC50 value of 0.61 ± 0.03 and 1.00 ± 0.02 μg/mL, respectively, demonstrating that the solid dispersions presented a significant increase in antioxidant activity (P < 0.05). Putting results together, it was possible to conclude there was the formation of quercetin-PVP K25 solid dispersion. 相似文献
163.
Medeiros MR Prado LA Fernandes VC Figueiredo SS Coppede J Martins J Fiori GM Martinez-Rossi NM Beleboni RO Contini SH Pereira PS Fachin AL 《Natural product communications》2011,6(2):193-196
Tabernaemontana catharinensis root bark ethanol extract, EB2 fraction and the MMV alkaloid (12-methoxy-4-methylvoachalotine) were evaluated for their antimicrobial activities. T. catharinensis ethanol extract was effective against both strains of the dermatophyte Trichophyton rubrum at concentrations of 2.5 mg/mL (wild strain) and 1.25 mg/mL (mutant strain), while the EB2 fraction and MMV alkaloid showed a strong antifungal activity against wild and mutant strains with MIC values of <0.02 and 0.16 mg/mL, respectively. The EB2 fraction showed a strong antibacterial activity against ATCC strains of S. aureus, S. epidermidis, E. coli and P. aeruginosa with MICs from <0.02 to 0.04 mg/mL, as well as against resistant clinical isolates species of Enterococcus sp, Klebsiella oxytoca, Citrobacter, K. pneumoniae, P. mirabilis, S. aureus, S. epidermidis, E. coli and P. aeruginosa with MIC values ranging from 0.04 to 0.08 mg/mL. The MMV alkaloid presented a MIC of 0.16 mg/mL against the strains of S. aureus and E. coli ATCC. For the resistant clinical isolates Enterococcus sp, Citrobacter, S. aureus, S. epidermidis, E. coli and P. aeruginosa the MIC of MMV ranged from 0.08 to 0.31 mg/mL. The chromatography analysis of the EB2 fraction revealed the presence of indole alkaloids, including MMV, possibly responsible for the observed antimicrobial activity. 相似文献
164.
The network loading problem (NLP) is a specialized capacitated network design problem in which prescribed point-to-point demand between various pairs of nodes of a network must be met by installing (loading) a capacitated facility. We can load any number of units of the facility on each of the arcs at a specified arc dependent cost. The problem is to determine the number of facilities to be loaded on the arcs that will satisfy the given demand at minimum cost.This paper studies two core subproblems of the NLP. The first problem, motivated by a Lagrangian relaxation approach for solving the problem, considers a multiple commodity, single arc capacitated network design problem. The second problem is a three node network; this specialized network arises in larger networks if we aggregate nodes. In both cases, we develop families of facets and completely characterize the convex hull of feasible solutions to the integer programming formulation of the problems. These results in turn strengthen the formulation of the NLP.Research of this author was supported in part by a Faculty Grant from the Katz Graduate School of Business, University of Pittsburgh. 相似文献
165.
We report the results of the Monte Carlo simulation of the phase diagram of fcc binary alloys using a 3-D Ising model with
nearest and next-nearest neighbour repulsive interactions. Calculations are carried out for a ratio of second- to first-neighbour
interaction energies of 0.4. The resulting phase diagram contains three superstructures A2B2, A2B and A5B, each separated by a disordered fcc phase. There was no evidence for the formation of an A3B phase. These results are in qualitative agreement with CVM results. 相似文献
166.
167.
Rita CagnoliFranco Ghelfi Ugo M PagnoniAndrew F Parsons Luisa Schenetti 《Tetrahedron》2003,59(50):9951-9960
The benzoylamino group was identified as a useful radical cyclization auxiliary that can be smoothly removed on hydro-de-halogenation of chlorinated N-substituted-pyrrolidin-2-ones with Raney-Ni. This methodology was successfully implemented in a new and appealing route to the anti-epileptic drug gabapentin. 相似文献
168.
169.
Rita Mehra 《Journal of Chemical Sciences》2003,115(2):147-154
Density and refractive index have been experimentally determined for binary liquid mixtures of hexadecane and heptadecane
with 1-butanol, 1-pentanol, 1-hexanol and 1-heptanol at 298.15, 308.15 and 318.15 K. A comparative study of Lorentz—Lorenz
(L-L), Weiner (W) and Heller (H), and Gladstone-Dale (G-D) relations for predicting the refractive index of a liquid has been
carried out to test their validity for the eight binaries over the entire mole fraction range of hexadecane and heptadecane
at the three temperatures. Comparison of various mixing rules has been expressed in terms of average percentage deviation.
The performance of the Lorentz-Lorenz and Heller relations is relatively better than that of the Weiner and Gladstone-Dale
relations. 相似文献
170.
Janak Singh Thomas P. Kissick Rita Fox Octavian Kocy Richard H. Mueller 《Journal of heterocyclic chemistry》1989,26(1):17-21
The β-lactam antibiotic Tigemonam 2 undergoes desulfation to the N-hydroxyazetidinone 4 , which rearranges to the isoxazolidin-5-one 6 . The structure of the rearrangement product 6 was confirmed by synthesis. 相似文献