Search results for "OXIDATION"

Beauvericin and ochratoxin A mycotoxins individually and combined in HepG2 cells alter lipid peroxidation, levels of reactive oxygen species and glut…

2020

The co-presence of more than one mycotoxin in food is being evidenced in last food surveys as reported in the literature. Beauvericin (BEA) is a non-legislated emergent mycotoxin while Ochratoxin A (OTA) has been widely studied and legislated. Concentration range individually studied was from 2.5 to 0.3 μM for BEA and from 25 to 3.1 μM for OTA; binary mixture [BEA + OTA] comprised concentrations of 1:10 ratio from [2.5 + 25] to [3.1 + 0.3] μM. Potential of toxicity of BEA in HepG2 cells was the highest at all times assayed (24, 48 and 72h). LPO was performed through malondyaldehyde (MDA) detection denoting in the binary mixture for [1.25 + 12.5] μM and at 24 and 72h the highest disturbance …

Effect of storage on quality parameters and phenolic content of Italian extra-virgin olive oils

2019

The quality of extra virgin olive oils is affected mainly by hydrolytic and oxidative reactions. The present paper investigated the changes of major and minor components and oxidation indices of three monovarietal extra virgin olive oils after 18 months of storage at room temperature and in dark glass bottles conditions. After storage, the basic quality parameters such as free acidity, peroxide values, extinction coefficients, fatty acids composition, chlorophyll and carotenoid content, did not exceed the upper limits set by European Community Regulations for extra-virgin olive oils. Given the importance of the phenolic fraction, UHPLC-HESI-MS metodology was used. A decrease in 3,4-DHPEA-ED…

Homogeneous Metal-Based Catalysis in Supercritical Carbon Dioxide as Reaction Medium

2016

Above 31.1 degrees C and 73.8 bar, carbon dioxide reaches the supercritical state, being transformed into a fluid (scCO(2)) that has attracted interest in the last few decades as reaction medium for several transition-metal-catalyzed organic transformations. The main feature of this fluid rests on its capability to dissolve large amounts of other gases such as hydrogen, carbon monoxide, ethylene, or even methane and light alkanes. In this manner, very high concentrations of these reactants are available for catalysis. In this contribution a review of the main achievements of the use of transition-metal complexes as catalysts in scCO(2) is presented.

Oxidative changes in Sicilian extra virgin olive oil under heating treatment detected by FTIR spectroscopy, viscosimetry and time-resolved luminescen…

2007

2015

Oxidative stress is thought to be one of the main mediators of neuronal damage in human neurodegenerative disease. Still, the dissection of causal relationships has turned out to be remarkably difficult. Here, we have analyzed global protein oxidation in terms of carbonylation of membrane proteins and cytoplasmic proteins in three different mammalian species: aged human cortex and cerebellum from patients with or without Alzheimer's disease, mouse cortex and cerebellum from young and old animals, and adult rat hippocampus and cortex subjected or not subjected to cerebral ischemia. Most tissues showed relatively similar levels of protein oxidation. However, human cortex was affected by sever…

Inverse solvent effects in the heterogeneous and homogeneous epoxidation of cis-2-heptene with [2-percarboxyethyl]-functionalized silica and meta-chl…

2014

The rate constants for the epoxidation of cis-2-heptene with [2-percarboxyethyl]-functionalized silica (1a) and meta-chloroperbenzoic acid (mCPBA) (1b) in different solvents have been determined at temperatures in the −10 to 40 °C range. The heterogeneous epoxidation exhibits a dependence of the reaction rate on solvent polarity opposite to its homogeneous counterpart and anomalous activation parameters in n-hexane, which are interpreted in terms of the surface-promoted solvent structure at the solid–liquid interface. The results show that highly polar solvents can strongly inhibit heterogeneous reactions performed with silica-supported reagents or catalysts.

Effect of Substituents on Partial Photocatalytic Oxidation of Aromatic Alcohols Assisted by Polymeric C3N4

2019

In the present work we scrutinize the effect of substituents in the phenyl ring of the benzyl alcohol on its photo-oxidation to the corresponding benzaldehyde driven by polymeric carbon nitride photocatalyst in aqueous medium. It has been established that electron donating (ED) substituents in para- and ortho-position with respect to the CH2OH-group promote the reactivity of the substrate without compromising the selectivity towards benzaldehyde formation, maintaining it in the range of 84–98 %, if compared to the unsubstituted molecule. The same observation is true for meta-substituted benzyl alcohol with an electron withdrawing (EW) group. On the other hand, the presence of ED-group in me…

Effect of heating of organo-montmorillonites under different atmospheres

2009

Abstract We studied the influence of heating on the behaviour of two organo-montmorillonites paying particular attention to the possible degradation effects of the organic modifier under different atmospheres. Hoffmann elimination and anucleophilic substitution on the nitrogen led to rapid degradation of the modifier. As confirmed by deconvoluted FTIR spectra, the presence of oxygen accelerated the degradation rate. The degradation products of the modifier (α-olefins transforming into various carboxyl compounds if oxygen is present) initially increased the basal spacing, followed by a collapse of the particle layers when the decomposition products migrated toward the surface and eventually …

Stabilisation of LDPE cross-linked in the presence of peroxidesII. FTIR study of chemical changes taking place in the LDPE–dicumyl peroxide–Irganox 1…

2000

Abstract The chemical changes taking place in the systems: LDPE–Irganox 1081, LDPE–dicumyl peroxide and LDPE–Irganox 1081–dicumyl peroxide, after homogenisation (in a rolling mill at 130°C) and after homogenisation and cross-linking (at 180°C and 5.0 MPa for 20 min) were investigated by FTIR. It was found that the OH groups in Irganox 1081 were in a bound form, and were most probably linked to the sulphur co-ordination centre. Further, the presence of dicumyl peroxide without Irganox 1081 in LDPE resulted in the formation of hydroperoxide groups at a temperature of 130°C, which were replaced by free hydroxy and carbonyl groups of a ketonic type after cross-linking. Simultaneous addition of …

Water oxidation catalyzed by molecular di- and nonanuclear Fe complexes: importance of a proper ligand framework.

2016

The synthesis of two molecular iron complexes, a dinuclear iron(III,III) complex and a nonanuclear iron complex, based on the di-nucleating ligand 2,2-(2-hydroxy-5-methyl-1,3-phenylene)bis(1H-benzo[d]imidazole-4-carboxylic acid) is described. The two iron complexes were found to drive the oxidation of water by the one-electron oxidant [Ru(bpy)(3)](3+). Funding Agencies|Knut and Alice Wallenberg Foundation; Swedish Research Council [621-2013-4872]; Carl Trygger Foundation; DFG (Metal Sites in Biomolecules: Structures, Regulation and Mechanisms) [IRTG 1422]; Swedish Energy Agency