Search results for " Radical"
showing 10 items of 757 documents
Ring splitting of azetidin-2-ones via radical anions
2012
The radical anions of azetidin-2-ones, generated by UV-irradiation in the presence of triethylamine, undergo ring-splitting via N-C4 or C3-C4 bond breaking, leading to open-chain amides. This reactivity diverges from that found for the neutral excited states, which is characterised by alpha-cleavage. The preference for beta-cleavage is supported by DFT theoretical calculations on the energy barriers associated with the involved transition states. Thus, injection of one electron into the azetidin-2-one moiety constitutes a complementary activation strategy which may be exploited to produce new chemistry.
Synthesis and antioxidant evaluation of novel silybin analogues
2006
In this work, we evaluated the antioxidant properties of the eight novel silybin analogues for their capacity to scavenge free radicals including superoxide anion radicals and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals in vitro. Compound 7d demonstrated an excellent antioxidant effect in scavenging superoxide anion free radical with an IC50 value of 26.5 microM, while the IC50 of quercetin (the reference compound) was 38.1 microM. Compounds 7b, 7e, 7h showed certain scavenging activities for both types of free radicals.
ESR and electrochemical studies of 2-acylpyridines and 6,6'-diacyl-2,2'-bipyridines.
2005
Abstract The ESR spectra of radicals obtained by electrolytic reduction of 2-acylpyridines and 6,6′-diacyl-2,2′-bipyridines were measured in dimethylsulfoxide (DMSO) and analyzed by quantum chemical calculations. The electrochemistry of these compounds was characterized using cyclic voltammetry, in DMSO solvent. The results showed a two step reduction mechanism, first wave was assigned to the generation of the correspondent free radical species, and the second wave was assigned to the dianion derivatives. AM1 and DFT calculations were performed to obtain the optimized geometries, theoretical hyperfine constants, and spin distributions, respectively. The theoretical results are in complete a…
Mitochondrial glutathione depletion by glutamine in growing tumor cells.
2000
The effect of L-glutamine (Gln) on mitochondrial glutathione (mtGSH) levels in tumor cells was studied in vivo in Ehrlich ascites tumor (EAT)-bearing mice. Tumor growth was similar in mice fed a Gln-enriched diet (GED; where 30% of the total dietary nitrogen was from Gln) or a nutritionally complete elemental diet (SD). As compared with non-tumor-bearing mice, tumor growth caused a decrease of blood Gln levels in mice fed an SD but not in those fed a GED. Tumor cells in mice fed a GED showed higher glutaminase and lower Gln synthetase activities than did cells isolated from mice fed an SD. Cytosolic glutamate concentration was 2-fold higher in tumor cells from mice fed a GED ( approximately…
The Radical Trap in Atom Transfer Radical Polymerization Need Not Be Thermodynamically Stable. A Study of the MoX3(PMe3)3 Catalysts
2005
The molybdenum(III) coordination complexes MoX(3)(PMe(3))(3) (X = Cl, Br, and I) are capable of controlling styrene polymerization under typical atom transfer radical polymerization (ATRP) conditions, in conjunction with 2-bromoethylbenzene (BEB) as an initiator. The process is accelerated by the presence of Al(OPr(i))(3) as a cocatalyst. Electrochemical and synthetic studies aimed at identifying the nature of the spin trap have been carried out. The cyclic voltammogram of MoX(3)(PMe(3))(3) (X = Cl, Br, I) shows partial reversibility (increasing in the order ClBrI) for the one-electron oxidation wave. Addition of X(-) changes the voltammogram, indicating the formation of MoX(4)(PMe(3))(3) f…
4-dimethylamino-3′,4′-dimethoxychalcone downregulates iNOS expression and exerts anti-inflammatory effects
2001
Abstract Reactive oxygen and nitrogen species contribute to the pathophysiology of inflammatory conditions. We have studied the effects of a novel superoxide scavenger, 4-dimethylamino-3′,4′-dimethoxychalcone (CH11) in macrophages and in vivo. CH11 has been shown to inhibit the chemiluminescence induced by zymosan in mouse peritoneal macrophages and the cytotoxic effects of superoxide. In the same cells, the modulation by superoxide of nitric oxide (NO) production in response to zymosan was investigated. CH11 was more effective than the membrane-permeable scavenger Tiron for inhibition of inducible nitric oxide synthase (iNOS) protein expression and nitrite production. We have shown that CH…
Bioactive aristolactams from Piper umbellatum.
2007
Four alkaloids named piperumbellactams A-D (1-4) were isolated from branches of Piper umbellatum together with known N-hydroxyaristolam II (5), N-p-coumaroyl tyramine (6), 4-nerolidylcatechol (7), N-trans-feruloyltyramine, E-3-(3,4-dihydroxyphenyl)-N-2-[4-hydroxyphenylethyl]-2-propenamide, beta-amyrin, friedelin, apigenin 8-C-neohesperidoside, acacetin 6-C-beta-d-glucopyranoside, beta-sitosterol, its 3-O-beta-d-glucopyranoside and its 3-O-beta-d-[6'-dodecanoyl]-glucopyranoside. Glycosidase inhibition, antioxidant and antifungal activities of these compounds were evaluated. Compounds 1-3 showed moderate alpha-glucosidase enzyme inhibition with IC50 values 98.07+/-0.44, 43.80+/-0.56 and 29.64…
HPLC-DAD profile of phenolic compounds and In vitro antioxidant activity of Ficus carica L. fruits from two Algerian varieties
2022
Ficus carica L., commonly known as the fig tree, is a plant belonging to the Moraceae family whose fruits are traditionally used for edible and therapeutic purposes. The study aimed to investigate the lyophilized aqueous extracts of two native Algerian fig varieties, azendjar (Az) and taamriouth (Ta), as a potential source of antioxidant compounds for possible use as ingredients in pharmaceuticals or nutraceuticals. The HPLC-DAD analysis revealed the presence of two phenolic acids (3,4-dihydroxybenzoic acid and vanillic acid) and two flavonoids (rutin and quercetin) at levels 3.67, 4.80, 84.16, and 6.87 µg/g respectively for Az variety extract, and 6.90, traces, 7.46 and 3.37 µg/g respectiv…
Phenolic Compounds Characterization and Antioxidant Properties of Monocultivar Olive Oils from Northeast Algeria
2020
In Algeria, the olive tree is one of the main fruit species and plays a very important socioeconomic role. The objective of this study was firstly, to identify and quantify the phenolics of some Algerian olive oils, and secondly, to assess the antioxidant activity of the samples. The olive oils used in this study were derived from Algerian cultivars, including Tefahi, Gelb Elfarroudj, Chemlal, and imported cultivar Manzanilla and Zebboudj. For this purpose, gas chromatography&mdash
Coffee and endothelial function: a battle between caffeine and antioxidants ?
2010
Although coffee is largely consumed by adults in Western countries, controversy exists about its impact on the cardiovascular system. We recently demonstrated that caffeinated and decaffeinated espresso coffee have different acute effects on endothelial function in healthy subjects, measured using flow-mediated dilation (FMD) of the brachial artery. In this study, we measured the anti-oxidant capacity of two coffee substances in terms of free stable radical 2,2-diphenyl-1-picryl-hydrazyl 50% inhibition (I(50) DPPH). The caffeinated coffee had a slightly higher anti-oxidant capacity than decaffeinated espresso coffee (I(50) DPPH: 1.13±0.02 vs 1.30±0.03 μl; P0.001). We suggest that the unfavo…