Search results for "Radical"
showing 10 items of 1401 documents
Cytotoxic Glial Swelling by Arachidonic Acid
1994
Arachidonic acid (AA, 20:4) is a major constituent of membrane phospholipids in brain tissue. Normally, the free fatty acid is present only in a small amount, but it accumulates under adverse conditions, such as ischemia or brain injury [1,9]. The release of free fatty acid involves activation of phospholipases and breakdown of membrane phospholipids. AA in particular is considered to mediate pathological processes. The polyunsaturated compound is a precursor of prostaglandins, leukotrienes, and oxygen-derived free radicals [11]. In cerebral ischemia concentrations of free AA of up to 0.5 mM/kg have been found in brain tissue [9].
Structural induced modifications in blends of polyamide with gamma irradiated low density polyethylene
1992
Abstract Blends of gamma irradiated and unirradiated low density polyethylene and polyamide 6 were made in order to study possible modifications induced by this irradiation. Results indicate that blends with gamma irradiated polyethylene have structure and properties significantly different with respect to blends made with the unirradiated one. This difference has been ascribed to the formation of functionalized groups in the polyethylene chains, which interact with polyamide.
γ-radiation-initiated polymerization of vinylidene fluoride in dense carbon dioxide
2002
The γ-ray-initiated batch polymerization of vinylidene fluoride (VF2) has been investigated in dense carbon dioxide under relatively mild operative conditions (T ≤ 40 °C and P < 25 MPa). When the initial VF2 molar concentration was increased from 3.4 to 6.4 mol/L, monomer conversion increased from 20 to 73%; a similar trend was observed for the number-average molecular weight and the molecular complexity of synthesized poly(vinylidene fluoride) (PVDF) as determined from rheological measurements. Under all adopted experimental conditions, a synthesized PVDF polymer was collected in the form of a white powder. Despite the inherent heterogeneous character of the polymerization process, a homog…
Cyclodextrins in Polymer Synthesis: Enantiodiscrimination in Free-Radical Polymerization of Cyclodextrin-Complexed Racemic N -Methacryloyl-D,L -pheny…
2003
The enantiodiscriminating polymerization of racemic cyclodextrin-complexed N-methacryloylphenylalanine methyl ester is investigated 1 H NMR spectra of the complexes with methylated β-cyclodextrin in D 2 O manifest splittings due to chiral recognition. The different stabilities of the diastereomeric complexes influence the kinetics of the homopolymerization, particularly at 0°C. An enrichment of the residual N-methacryloyl-L-phenylalanine methyl ester of 14% was achieved after 21 h of polymerization.
Overview on oxidation mechanisms of organic compounds by TiO2 in heterogeneous photocatalysis
2012
This review provides the reader with a general overview on heterogeneous photocatalytic oxidation mechanisms in the presence of TiO2, with a special address to conversion of aliphatic and aromatic organic species. The aim was to clarify the steps of the photo-oxidation of the various classes of compounds and to relate them with the properties of the catalysts and the experimental conditions used. Reactions carried out to perform complete degradation and photocatalytic partial oxidations have been deeply discussed. Recent isotopic studies highlighted new reaction pathways concerning partial oxidation of alcohols to aldehyde and oxidation of benzene while EPR investigations confirmed that not…
The chemistry of melatonin's interaction with reactive species
2002
Melatonin has been shown to be an effective antioxidant in a number of experimental models both in vitro and in vivo. Considering the data available, it is now clear that the indoleamine is involved in antioxidative mechanisms more complex than originally envisaged. These range from the direct radical scavenging of a variety of radicals and reactive species to the control and/or modulation of a number of processes which may trigger a redox imbalance between antioxidant and prooxidant species. This review focuses on the direct radical scavenging activity of melatonin and provides a summary of the mechanisms of the reactions between the indoleamine and reactive species in pure chemical soluti…
Lipoperoxyl Radical Scavenging and Antioxidative Effects of Red Beet Pigments
2012
Aerobic life is characterized by a steady formation of reactive oxygen species and free radicals, which is almost entirely counteracted by endogenous primary and secondary antioxidant systems. Maintenance of these systems is then imperative to ensure a continuous defense to cells and to avoid conditions known as oxidative stress. Apart from antioxidant vitamins, many compounds from the plant kingdom are now considered very helpful to maintain a proper cell redox balance. Among them, betalain pigments have received recent attention. Betanin (betanidin-5-O-β glucoside) is the main betacyanin from red beet. Redox potential, ability to interact with lipid structures and bioavailability in human…
Contact probe voltammetry for in situ monitoring of the reactivity of phenolic tomato (Solanum lycopersicum L.) compounds with ROS
2015
The application of an in situ electrochemical contact probe methodology for monitoring reactivity of antioxidant polyphenolic compounds in tomato fruits is described. Upon electrochemical generation of reactive oxygen species (ROS), characteristic voltammetric responses were recorded for compounds resulting from the reaction of such species with tomato compounds. This suggests that new electrochemically oxidizable compounds are generated from the oxidation of highly reactive polyphenolic compounds with ROS. Therefore, an evaluation of the antioxidant capacity of such species could be made from voltammetric data for different tomato varieties.
ChemInform Abstract: Investigations Concerning the COX/5-LOX Inhibiting and Hydroxyl Radical Scavenging Potencies of Novel 4,5-Diaryl Isoselenazoles.
2008
The aim of this study was to investigate 4,5-diaryl isoselenazoles as multiple target non-steroidal anti-inflammatory drugs (MTNSAIDs) which can intervene into the inflammatory processes via different mechanisms of action creating a new class of compounds. Here we describe the synthesis of COX/LOX inhibitors which additionally reduce the level of reactive oxygen species, such as hydroxyl radicals which are well known for supporting inflammation processes in Parkinson's disease, Alzheimer's disease and rheumatoid arthritis.
Biological Activity of Flavonoids Copper Complexes
2005
Three flavonoid copper(II) complexes Cu2(quercetin)(CH3COO)3(CH3OH) (1), Cu(anthrarufin)(CH3COO)·1/2H2O (2) and Cu(naringin)(OCH3)(CH3OH)2 (3) have been synthesized and characterized by elemental analysis, IR, electronic absorption and EPR (X-band) spectroscopy. The complexes have a strong protective action over the Δsod1 mutant of S. cerevisiae against reactive oxygen radicals generated by an external source of free radicals (H2O2 or the superoxide-generating, menadione). On the other hand, the complexes cleave DNA efficiently even in the absence of reducing agents. The main reactive oxygen species responsible for the DNA strand cleavage have been determined using radical scavengers. A pro…