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排序方式: 共有1479条查询结果,搜索用时 15 毫秒
1.
Prof. Andrea Baier Dr. Anne Kokel Dr. William Horton Ewa Gizińska Dr. Garima Pandey Prof. Ryszard Szyszka Prof. Béla Török Prof. Marianna Török 《ChemMedChem》2021,16(12):1927-1932
A set of novel hydrazone derivatives were synthesized and analyzed for their biological activities. The compounds were tested for their inhibitory effect on the phosphorylating activity of the protein kinase CK2, and their antioxidant activity was also determined in three commonly used assays. The hydrazones were evaluated for their radical scavenging against the DPPH, ABTS and peroxyl radicals. Several compounds have been identified as good antioxidants as well as potent protein kinase CK2 inhibitors. Most hydrazones containing a 4-N(CH3)2 residue or perfluorinated phenyl rings showed high activity in the radical-scavenging assays and possess nanomolar IC50 values in the kinase assays. 相似文献
2.
In this work, the kinetics and mechanism of free-radical polymerisation of glycidyl methacrylate (GMA) using potassium peroxydisulphate
(PDS) as water soluble initiator in the presence of synthesized 1, 4-Bis (tributyl methyl ammonium) benzene dichloride (TBMABDC)
as multi-site phase transfer catalyst (MPTC) was studied. The polymerisation reactions were carried out under inert and unstirred
conditions at constant temperature of 60 ± 1°C in cyclohexane/water biphase media. The role of concentrations of monomer,
initiator, catalyst and volume fraction of aqueous phase, solvent polarity and temperature on the rate of polymerisation (Rp)
was ascertained. The order with respect to monomer and initiator was found to be unity. The order with respect to catalyst
was found to be 0.51. The rate of polymerisation is independent of ionic strength and pH of the medium. However, an increase
in the polarity of solvent has slightly increased the Rp value. Based on the results obtained, a suitable kinetic scheme has
been proposed to account for the experimental observations and its significance discussed. 相似文献
3.
A non-invasive headspace analysis method to measure rate and amount of oxygen uptake in oxygen-scavenging polymers is presented. Oxygen uptake data for metal-catalyzed poly(1,4-butadiene) at 30 °C are provided to illustrate the method. These data were obtained by measuring oxygen headspace concentration above the scavenging polymer with an OxySense® 200T non-invasive oxygen sensor, and, for comparison, oxygen uptake was measured with an analytical balance. Excellent agreement was observed between these two independent experiments. 相似文献
4.
Alkyl radicals produced in the indirect reduction of alkyl halides or alkyldimethylsulfonium salts by electrochemically generated aromatic radical anions couple fast with the latter and alkylated or dialkylated dihydro compounds are formed. Rate constants measured for the coupling reaction between on one hand methyl, primary, secondary and tertiary alkyl radicals as well as benzyl and cumyl radicals and on the other hand a wide spectrum of electrochemically generated aromatic radical anions are found to be about 1×109 M−1 s−1. Previous measurements of coupling rate constants for primary alkyl radicals have been re-evaluated since they were affected by the presence of an SN2 reaction occurring between the alkyl halides used as radical precursors and the aromatic radical anions. New experiments are also included using alkyldimethylsulfonium salts as precursors in order to prevent such SN2 artefacts. It is concluded that sterical hindrance does not play a significant role for the radical-radical anion coupling reactions. In general the rate constants for the coupling reactions are all close to 109 M−1 s−1. 相似文献
5.
6.
本研究以济源冬凌草多糖为原料,选用化学合成方法对多糖进行结构修饰。采用UV、FT-IR、SEM、TGA、HPLC等方法对冬凌草多糖以及硒多糖结构特征进行了表征;通过DPPH(1,1-二苯基-2-三硝基苯肼)自由基法、羟自由基法等4种方法对其抗氧化活性进行了探究。结果:制备的硒多糖中硒质量分数为1.35 mg/g。硒化修饰后,冬凌草多糖的基本骨架得到保留,单糖种类未发生改变,但其分解温度降低、稳定性下降,多糖形貌也发生明显变化,球状与条状形貌增多,片状形貌减少。此外,在体外抗氧化性实验中,当硒多糖质量浓度为1.6mg/mL时,对DPPH自由基、ABTS自由基、羟自由基清除率分别为68.68%、86.69%、45.12%,均强于冬凌草多糖。 相似文献
7.
Francis W. Maloba Michael L. Rooney Paul Wormell Minh Nguyen 《Journal of the American Oil Chemists' Society》1996,73(2):181-185
The oxidative stability of sunflower oil (SFO) was measured during storage at 23 and 37°C in the presence of a novel oxygen-scavenging
film that contained polyfuryloxirane (PFO). Commercially refined and deodorized SFO was stored in a lighted room in sealed
transparent packages containing either PFO film or an antioxidant, 0.02% butylated hydroxytoluene (BHT). Oxidative stability
was evaluated by determination of peroxide values and gas-chromatographic measurement of headspace hexanal. SFO stored in
the presence of the oxygen-scavenging film was more stable than oil stored without the film, or than film stored with 0.02%
BHT. The PFO film scavenges oxygen through energy-transfer sensitization of singlet oxygen. The film is doped with eosin and
the naturally-occurring dye, curcumin, which absorb over a wide range of visible wavelengths. Curcumin transfers its absorbed
energy to eosin, which sensitizes the production of singlet oxygen. The singlet oxygen is scavenged by PFO. The use of two
dyes increases the efficiency of the sensitization process, reducing the illumination time and intensity required for effective
oxygen scavenging. 相似文献
8.
M.?NaczkEmail author R.?B.?Pegg R.?Zadernowski F.?Shahidi 《Journal of the American Oil Chemists' Society》2005,82(4):255-260
Possible use of canola hulls as a source of natural anti-oxidants was explored. Cyclone canola hulls were extracted with methanol
(30 to 80%, vol/vol) and acetone (30 to 80%, vol/vol). The free radical-scavenging activity of phenolic extracts so prepared
was evaluated using the 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS) radical ion (ABTSo−), 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, and chemiluminescence assays. The total content of phenolics in prepared
extracts from canola hulls ranged from 15 to 136 mg sinapic acid equivalents per gram of extract. Higher levels of condensed
tannins were detected in the acetone extracts than in the corresponding methanolic counterparts. Seventy and 80% (vol/vol)
acetone extracts displayed markedly stronger antioxidant activity than any of the other extracts investigated. Statistically
significant linear correlations were found between TEAC (Trolox equivalent antioxidant capacity) values (expressed in mM of
Trolox equivalents per gram of extract) and total pehnolics, TEAC and total condensed tannins (i.e., determined using the
modified vanillin and pronthocyanidin assays), as well as TEAC and protein precipitation activity of phenolic extracts (i.e.,
measured using the dye-labeled assay). The antioxidant activities of extracts as determined by the ABTSo− radical ion assay correlated highly with those of the chemiluminescence and DPPH radical assays. 相似文献
9.
The process of ozonation of glyoxal in aqueous solution has been studied by following its chemical and kinetic evolution. Results show that the oxidative process leads to formation of carboxylic functions and carbon dioxide according to a constant selectivity ratio at varying conversion degree.. Comparison between the oxygen amounts of reaction products and the corresponding ozone consumptions reveals that molecular oxygen takes part in the reaction process. System behavior is explained on the basis of radical reaction mechanism. 相似文献
10.
Nikolaos?Nenadis Maria?TsimidouEmail author 《Journal of the American Oil Chemists' Society》2002,79(12):1191-1195
Rapid 1,1-diphenyl-2-picrylhydrazyl (DPPH•) tests are often applied to classify the scavenging activity of phenolic compounds (AH). Published analytical protocols differ
in more than one experimental condition, and results for the relative order or magnitude of activity are often contradictory.
In this work, parameters such as duration of test, [AH]/[DPPH•] molar ratio, and solvent effects were examined and discussed. The test duration and the value of the [AH]/[DPPH•] ratio did not influence the order of activity among tested antioxidants. Ethanol, commonly used as solvent in such tests,
was compared with acetonitrile and tert-butyl alcohol. Solvent properties such as the ability to form hydrogen bonds with the AH seem to influence the level of the
relative activity (%RSA). Higher %RSA values were observed in ethanol. The activity of the most polar compounds was affected
the most, and in some cases (caffeic, dihydrocaffeic, and rosmarinic acids) the order of activity was changed owing to different
kinetics. Standardization of the analytical protocol should include a 20-min reaction period and a molar ratio that permits
attainment of a 60–80% RSA value for the most potent antioxidant. Solvent choice is critical for classifying activity. Safe
classification can be based only on results from kinetic studies. 相似文献