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81.
[reaction: see text] Alpha-nitro ketones can be transformed selectively into trialkyl-substituted pyrazines via reaction with alpha-amino ketones using octyl viologen as an electron-transfer reagent. The new synthetic method, and the optimal reaction conditions that allow for the regiochemical control, are described. 相似文献
82.
Two procedures are proposed for the potentiometric determination of Ag(I), Pd(II) and Au(III) in binary mixtures, by titration with potassium iodide solution, and use of a commercial iodide electrode as sensor. In the first procedure, two aliquots of the mixture are titrated, at pH 2.0 ± 0.2 and 9.0 ± 0.2, adjusted with dilute sulphuric acid and ammonia solution. At pH 2.0, the titrant reacts with both metals, whereas at pH 9.0, Ag(I) is the only reactant. The second procedure utilizes titration of two aliquots of the mixture in the presence and absence of a selective masking agent. The methods have been applied to the determination of these metals in some jewellery alloys. 相似文献
83.
Ahmad J. Almalki Tarek S. Ibrahim Ehab S. Taher Mamdouh F. A. Mohamed Mahmoud Youns Wael A. H. Hegazy Amany M. M. Al-Mahmoudy 《Molecules (Basel, Switzerland)》2022,27(3)
Since the synthesis of prontosil the first prodrug shares their chemical moiety, sulfonamides exhibit diverse modes of actions to serve as antimicrobials, diuretics, antidiabetics, and other clinical applications. This inspiring chemical nucleus has promoted several research groups to investigate the synthesis of new members exploring new clinical applications. In this study, a novel series of 5(4H)-oxazolone-based-sulfonamides (OBS) 9a–k were synthesized, and their antibacterial and antifungal activities were evaluated against a wide range of Gram-positive and -negative bacteria and fungi. Most of the tested compounds exhibited promising antibacterial activity against both Gram-positive and -negative bacteria particularly OBS 9b and 9f. Meanwhile, compound 9h showed the most potent antifungal activity. Moreover, the OBS 9a, 9b, and 9f that inhibited the bacterial growth at the lowest concentrations were subjected to further evaluation for their anti-virulence activities against Pseudomonas aeruginosa and Staphylococcus aureus. Interestingly, the three tested compounds reduced the biofilm formation and diminished the production of virulence factors in both P. aeruginosa and S. aureus. Bacteria use a signaling system, quorum sensing (QS), to regulate their virulence. In this context, in silico study has been conducted to assess the ability of OBS to compete with the QS receptors. The tested OBS showed marked ability to bind and hinder QS receptors, indicating that anti-virulence activities of OBS could be due to blocking QS, the system that controls the bacterial virulence. Furthermore, anticancer activity has been further performed for such derivatives. The OBS compounds showed variable anti-tumor activities, specifically 9a, 9b, 9f and 9k, against different cancer lines. Conclusively, the OBS compounds can serve as antimicrobials, anti-virulence and anti-tumor agents. 相似文献
84.
Yingying Wang Yan-Xin Chen Tarek Barakat Tian-Ming Wang Alain Krief Yu-Jia Zeng Marvin Laboureur Luca Fusaro Hong-Gang Liao Bao-Lian Su 《Journal of Energy Chemistry》2021,(5):141-151
The"one pot"simultaneous carbon coating and doping of TiO2 materials by the hydrolysis of TiCl4 in fructose is reported.The synergistic effect of carbon doping and coating of TiO2 to significantly boost textural,optical and electronic properties and photocurrent of TiO2 for high performance visible light H2 production from water splitting has been comprehensively investigated.Carbon doping can significantly increase the thermal stability,thus inhibiting the phase transformation of the Titania material from anatase to rutile while carbon coating can suppress the grain aggregation of TiO2.The synergy of carbon doping and coating can not only ensure an enhanced narrowing effect of the electronic band gap of TiO2 thus extending the absorption of photocatalysts to the visible regions,but also promote dramatically the separation of electron-hole pairs.Owing to these synergistic effects,the carbon coated and doped TiO2 shows much superior photocatalytic activity for both degradation of organics and photocatalytic/photoelectro chemical(PEC)water splitting under simulated sunlight illumination.The photocatalytic activity of obtained materials can reach 5,4 and 2 times higher than that of pristine TiO2,carbon doped TiO2 and carbon coated TiO2,respectively in the degradation of organic pollutants.The carbon coated and doped TiO2 materials exhibited more than 37 times and hundreds of times photocurrent enhancement under simulated sunlight and visible light,respectively compared to that of pristine TiO2.The present work providing new comprehensive understanding on carbon coating and doping effect could be very helpful for the development of advanced TiO2 materials for a large series of applications. 相似文献
85.
The electrochemical oxidation of the three fluoroquinolone drugs FQs: gatifloxacin GTF, moxifloxacin MXF and sparfloxacin SPF, at the bare and DNA‐modified glassy carbon electrodes has been studied by voltammetric techniques. The three FQs showed one irreversible oxidation peak at potential range 0.85–0.91 V vs. Ag‐AgCl, in phosphate buffer of pH 7.0. Differential pulse voltammetry (DPV) and UV‐absorption spectroscopic techniques were employed to probe the interaction between the FQs and calf thymus double stranded deoxyribonucleic acid (ds CT‐DNA). From electrochemical data, the binding constant between DNA and the gatifloxacin, moxifloxacin and sparfloxacin are calculated to be 3228, 2596 and 2857 M?1 respectively. Based on electrochemical and spectroscopic results, the mode of binding of fluoroquinolone to DNA through combined effect of intercalation and electrostatic interaction was concluded. A detection scheme based on a preconcentration and differential pulse voltammetric (DPV) determination at dsDNA modified glassy carbon electrode (DNA/GCE) was proposed for the trace determination of the studied analytes. The developed method was successfully applied to the determination of the FQs in pharmaceutical formulations. 相似文献
86.
Adel M. Ahmad Hamdoon A. Mohammed Tarek M. Faris Abeer S. Hassan Hebatallah B. Mohamed Mahmoud I. El Dosoky Esam M. Aboubakr 《Molecules (Basel, Switzerland)》2021,26(24)
The study aimed to develop a new glutathione (GSH) oral formulation to enhance the delivery of GSH and counter the nephrotoxicity of the anticancer drug, cyclophosphamide (CP). A nanostructured lipid carrier glutathione formulation (GSH-NLCs) composed of glutathione (500 mg), stearic and oleic acid (300 mg, each), and Tween® 80 (2%, w/v) was prepared through the emulsification-solvent-evaporation technique, which exhibited a 452.4 ± 33.19 nm spheroidal-sized particulate material with narrow particle size distributions, −38.5 ± 1.4 mV zeta potential, and an entrapment efficiency of 79.8 ± 1.9%. The GSH formulation was orally delivered, and biologically tested to ameliorate the CP-induced renal toxicity in a rat model. Detailed renal morphology, before and after the GSH-NLCs administration, including the histopathological examinations, confirmed the ameliorating effects of the prepared glutathione formulation together with its safe oral delivery. CP-induced oxidative stress, superoxide dismutase depletion, elevation of malondialdehyde levels, depletion of Bcl-2 concentration levels, and upregulated NF-KB levels were observed and were controlled within the recommended and near normal/control levels. Additionally, the inflammatory mediator marker, IL-1β, serum levels were marginally normalized by delivery of the GHS-NLCs formulation. Oral administration of the pure glutathione did not exhibit any ameliorating effects on the renal tissues, which suggested that the pure glutathione is reactive and is chemically transformed during the oral delivery, which affected its pharmacological action at the renal site. The protective effects of the GSH-NLCs formulation through its antioxidant and anti-inflammatory effects suggested its prominent role in containing CP-induced renal toxicity and renal tissue damage, together with the possibility of administrating higher doses of the anticancer drug, cyclophosphamide, to achieve higher and effective anticancer action in combination with the GSH-NLCs formulation. 相似文献
87.
Tarek Benameur Raffaella Soleti Maria Antonietta Panaro Maria Ester La Torre Vincenzo Monda Giovanni Messina Chiara Porro 《Molecules (Basel, Switzerland)》2021,26(16)
The nutrients and their potential benefits are a new field of study in modern medicine for their positive impact on health. Curcumin, the yellow polyphenolic compound extracted from Curcuma longa species, is widely used in traditional Ayurvedic medicine to prevent and contrast many diseases, considering its antioxidant, immunomodulatory, anti-inflammatory, anti-microbial, cardio-protective, nephron-protective, hepato-protective, anti-neoplastic, and anti-rheumatic proprieties. In recent years, the investigations of curcumin have been focused on its application to aging and age-associated diseases. Aging is a physiological process in which there is a decreasing of cellular function due to internal or external stimuli. Oxidative stress is one of the most important causes of aging and age-related diseases. Moreover, many age-related disorders such as cancer, neuroinflammation, and infections are due to a low-grade chronic systemic inflammation. Curcumin acting on different proteins is able to contrast both oxidative stress than inflammation. In the brain, curcumin is able to modulate inflammation induced by microglia. Finally in brain tumors curcumin is able to reduce tumor growth by inhibition of telomerase activity. This review emphasizes the anti-aging role of curcumin focusing on its mechanism to counteract aging in the brain. Moreover, new formulations to increase the bioavailability of curcumin are discussed. 相似文献
88.
Tarek Boudiar Boualem Harfi Maria del Mar Contreras Antonio Segura-Carretero 《Natural product research》2019,33(15):2208-2214
Rosmarinus eriocalyx (rosemary or Elyazir) is an endemic species growing in arid steppe and rocky mountain in the South-West Algeria. This plant is well known in Algeria and Morocco due to its medicinal properties. However, little is known about its phytochemical composition. For this purpose, natural antioxidant compounds from R. eriocalyx were recovered by solid-liquid extraction and characterized by reversed-phase high-performance liquid chromatography coupled to quadrupole-time-of-flight mass spectrometry using negative and positive ionization modes. This analytical methodology enabled the characterization of 101 compounds, which were distributed in five major categories namely hydroxycinnamic acid derivatives, hydroxybenzoic acid derivatives, flavonoids, phenolic diterpenes and phenolic triterpenes. Moreover, the studied extract generally showed free radical-scavenging and reductive abilities in the range of butylated hydroxyanisole, butylated hydroxytoluene, α-tocopherol, and ascorbic acid. Therefore, the result suggests that the aqueous-methanolic extract of R. eriocalyx could serve as a potential source of antioxidants. 相似文献
89.
Preparation of high molecular weight polybenzoxazine prepolymers containing siloxane unites and properties of their thermosets 总被引:1,自引:0,他引:1
Tsutomu Takeichi Takuya Kano Tarek Agag Takehiro Kawauchi Nobuyuki Furukawa 《Journal of polymer science. Part A, Polymer chemistry》2010,48(24):5945-5952
High‐molecular‐weight polybenzoxazine prepolymers containing polydimethylsiloane unit in the main‐chain have been synthesized from α,ω‐bis(aminopropyl)polydimethylsiloxane (PDMS) (molecular weight = 248, 850, and 1622) and bisphenol‐A with formaldehyde. Moreover, another type of prepolymers was prepared using methylenedianiline (MDA) as codiamine with PDMS. The weight average molecular weight of the obtained prepolymers was estimated from size exclusion chromatography to be in the range of 8000–11,000. The chemical structures of the prepolymers were investigated by 1H NMR and IR analyses. The prepolymers gave transparent free standing films by casting their dioxane solution. The prepolymer films after thermally cured up to 240 °C gave brown colored transparent and flexible polybenzoxazine films. Tensile test of the films revealed that the elongation at break increased with increasing the molecular weight of PDMS unit. Dynamic mechanical analysis of the thermosets showed that the Tgs were as high as 238–270 °C. The thermosets also revealed high thermal stability as evidenced by the 5% weight loss temperatures in the range of 324–384 °C from thermogravimetic analysis. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
90.
Tarek M. Trad Kyle B. Donley David C. Look Kurt G. Eyink David H. Tomich Curtis R. Taylor 《Journal of Crystal Growth》2010,312(24):3675-3679
ZnO nanoparticles as small as 80 nm were successfully synthesized using a modified vapor phase transport (VPT) process at substrate temperatures as low as 222 °C. Particle size distribution and morphology were characterized by scanning electron microscopy and atomic force microscopy. Energy dispersive X-ray spectroscopy and X-ray diffraction indicate the synthesis of high quality crystalline ZnO structures. Low temperature (4.2 K) photoluminescence (PL) spectroscopy was used to characterize the optical quality of the nanoparticles. Ultraviolet emission and a nanostructure specific feature at 3.366 eV are strong in the PL spectra. The 3.366 eV feature is observed to predominate the spectrum with decrease in particle size. This size effect corroborates the luminescence as a nanostructure-specific surface related exciton feature as previously speculated in the literature. In addition, self-assembled ZnO mesoparticles (>100 nm) were realized by increasing the growth time. Low growth temperatures of the particles allow for their potential utilization in flexible organic hybrid optoelectronics. However, this work focuses mainly on the modified synthesis and optical characterization of nanoparticles. 相似文献