Use of ESR to Investigate Formation of Free Radicals on Compounding Rubbers with Carbon Blacks

1978 ◽  
Vol 51 (1) ◽  
pp. 81-88 ◽  
Author(s):  
M. Jamroz˙ ◽  
K. Kozłowski ◽  
M. Sieniakowski ◽  
B. Jachym
Keyword(s):  
Free Radicals ◽  
Free Radical ◽  
Radical Formation ◽  
Chemical Interactions ◽  
Carbon Blacks ◽  
Physicochemical State ◽  
Free Radical Formation ◽  
Open Question ◽  
Rubber Filler

Abstract The problem of rubber reinforcement is of great importance in rubber technology. Free radicals formed during mastication play an important role in the reinforcement of the rubber-filler system. The reinforcement of rubber systems is usually explained in terms of chemical interactions between rubber and filler; however, there are also opinions that the interactions are physical in nature. So far, the mechanism of reinforcement is an open question. Undoubtedly, reinforcement is influenced by free radicals formed during mastication and the physicochemical state of the surface of active fillers. The formation of free radicals during plasticization of rubbers has been already reported. Investigations by an ESR technique of free-radical formation during compounding of rubbers with various carbon blacks are described in the present paper.

scholarly journals Influence of Temperature on Free Radical Generation in Propolis-Containing Ointments

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Paweł Olczyk ◽  
Pawel Ramos ◽  
Katarzyna Komosinska-Vassev ◽  
Lukasz Mencner ◽  
Krystyna Olczyk ◽  
...  
Keyword(s):  
Free Radicals ◽  
Free Radical ◽  
Heating Temperature ◽  
Radical Formation ◽  
Paramagnetic Resonance ◽  
Influence Of Temperature ◽  
Spin Lattice ◽  
Influence Of Temperature On ◽  
Free Radical Formation ◽  
C 50

Free radicals thermally generated in the ointments containing propolis were studied by electron paramagnetic resonance (EPR) spectroscopy. The influence of temperature on the free radical concentration in the propolis ointments was examined. Two ointment samples with different contents of propolis (5 and 7%, resp.) heated at temperatures of 30°C, 40°C, 50°C, and 60°C, for 30 min., were tested. Homogeneously broadened EPR lines and fast spin-lattice interactions characterized all the tested samples. Free radicals concentrations in the propolis samples ranged from 1018 to 1020 spin/g and were found to grow in both propolis-containing ointments along with the increasing heating temperature. Free radical concentrations in the ointments containing 5% and 7% of propolis, respectively, heated at temperatures of 30°C, 40°C, and 50°C were only slightly different. Thermal treatment at the temperature of 60°C resulted in a considerably higher free radical formation in the sample containing 7% of propolis when related to the sample with 5% of that compound. The EPR examination indicated that the propolis ointments should not be stored at temperatures of 40°C, 50°C, and 60°C. Low free radical formation at the lowest tested temperatures pointed out that both examined propolis ointments may be safely stored up to the temperature of 30°C.

scholarly journals Hydrogen Peroxide Effects on Natural-Sourced Polysacchrides: Free Radical Formation/Production, Degradation Process, and Reaction Mechanism—A Critical Synopsis

Foods ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 699
Author(s):  
Chigozie E. Ofoedu ◽  
Lijun You ◽  
Chijioke M. Osuji ◽  
Jude O. Iwouno ◽  
Ngozi O. Kabuo ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Free Radicals ◽  
Free Radical ◽  
Structural Characteristics ◽  
Radical Formation ◽  
Research Attention ◽  
Natural Sources ◽  
Polysaccharide Degradation ◽  
Free Radical Formation

Numerous reactive oxygen species (ROS) entities exist, and hydrogen peroxide (H2O2) is very key among them as it is well known to possess a stable but poor reactivity capable of generating free radicals. Considered among reactive atoms, molecules, and compounds with electron-rich sites, free radicals emerging from metabolic reactions during cellular respirations can induce oxidative stress and cause cellular structure damage, resulting in diverse life-threatening diseases when produced in excess. Therefore, an antioxidant is needed to curb the overproduction of free radicals especially in biological systems (in vivo and in vitro). Despite the inherent properties limiting its bioactivities, polysaccharides from natural sources increasingly gain research attention given their position as a functional ingredient. Improving the functionality and bioactivity of polysaccharides have been established through degradation of their molecular integrity. In this critical synopsis; we articulate the effects of H2O2 on the degradation of polysaccharides from natural sources. Specifically, the synopsis focused on free radical formation/production, polysaccharide degradation processes with H2O2, the effects of polysaccharide degradation on the structural characteristics; physicochemical properties; and bioactivities; in addition to the antioxidant capability. The degradation mechanisms involving polysaccharide’s antioxidative property; with some examples and their respective sources are briefly summarised.

scholarly journals Influence of Spray-Drying and Room Temperature Storage on the Anti- and Prooxidant Properties of Fermented Juçara Pulp

2020 ◽  
Vol 58 (1) ◽  
pp. 29-37
Author(s):  
Karla Bigetti Guergoletto ◽  
Kamila Landucci Bonifácio ◽  
Décio Sabbatini Barbosa ◽  
Daniel Farinha Valezi ◽  
Aroldo Salviato ◽  
...  
Keyword(s):  
Free Radicals ◽  
Free Radical ◽  
Antioxidant Capacity ◽  
Spray Drying ◽  
Room Temperature ◽  
Gum Arabic ◽  
Radical Formation ◽  
Total Phenolic ◽  
Free Radical Formation ◽  
And Storage

Many fruits and vegetables contain compounds with antioxidant properties, but the processing and storage conditions of the food industry may damage these beneficial compounds and produce free radicals that are associated with oxidative stress. This study aims to evaluate in vitro the antioxidant capacity and prooxidant effects of juçara pulp fermented with Lactobacillus reuteri or Lactobacillus plantarum before and after spray-drying with maltodextrin, gum arabic or gelatin and storage at 25 °C for 90 days. The antioxidant capacity was assessed by measuring the ability to scavenge reactive oxygen species (ROS) in the neutrophil respiratory burst and free radical 2,2-diphenyl-1-picryl-hydrazyl (DPPH), and by determining the total phenolic content. The prooxidant effects were analyzed as free radical formation measured by electronic paramagnetic resonance (EPR). Fermentation by both bacteria increased the antioxidant activity, while the spray-drying process decreased the content of phenolic compounds (65-85 %) and the DPPH scavenging ability, depending on the carrier usage. All of the samples inhibited ROS in the neutrophil burst, and the juçara pulp fermented by L. reuteri and dried with gum arabic exhibited the best performance. Spray-drying did not influence the intensity or type of free radicals detected by EPR. However, storage at room temperature decreased the antioxidant capacity and increased free radical formation.

Blue ‘turn-on’ fluorescent probes for the direct detection of free radicals and nitric oxide in Pseudomonas aeruginosa biofilms

2016 ◽  
Vol 14 (7) ◽  
pp. 2272-2281 ◽  
Author(s):  
Mina Barzegar Amiri Olia ◽  
Athanasios Zavras ◽  
Carl H. Schiesser ◽  
Stefanie-Ann Alexander
Keyword(s):  
Nitric Oxide ◽  
Pseudomonas Aeruginosa ◽  
Free Radicals ◽  
Free Radical ◽  
Fluorescent Probes ◽  
Direct Detection ◽  
Radical Formation ◽  
Turn On ◽  
Blue Cell ◽  
Free Radical Formation

Novel blue cell-permeable ‘turn-on’ fluorescent probes have been developed to visualize and quantify nitric oxide and free radical formation and reaction within aPseudomonas aeruginosabiofilm.

Spectrochemistry of Polycarbohydrate Free Radicals Generated by Argon Plasmolysis: Effect of Tertiary Structure on Free Radical Formation

1994 ◽  
Vol 98 (44) ◽  
pp. 11301-11307 ◽  
Author(s):  
Masayuki Kuzuya ◽  
Kazue Morisaki ◽  
Junji Niwa ◽  
Yukinori Yamauchi ◽  
Kaijun Xu
Keyword(s):  
Free Radicals ◽  
Free Radical ◽  
Tertiary Structure ◽  
Radical Formation ◽  
Free Radical Formation

Interaction of cytokinins with lipid-associated oxy free radicals during senescence: a prospective mode of cytokinin action

1984 ◽  
Vol 62 (12) ◽  
pp. 2943-2949 ◽  
Author(s):  
Ya'acov Y. Leshem
Keyword(s):  
Free Radicals ◽  
Free Radical ◽  
Xanthine Oxidase ◽  
Radical Scavenging ◽  
Free Radical Scavenger ◽  
Radical Formation ◽  
Radical Scavenger ◽  
Substrate Affinity ◽  
Xanthine Oxidase Inhibitors ◽  
Free Radical Formation

In senescence physiology, experimental data indicate causative relationships among cytokinin, lipoxygenation, anti-oxidation, and lipid-associated free radical scavenging. During both normal and induced senescence, there is a rise in lipoxygenase (LOX) which catalyzes the oxidation of polyunsaturated fatty acids containing the cis, cis-1,4-pentadiene configuration. These include linoleic and linolenic acids, which are of common occurrence in plants and inter alia may be situated in membranal phospholipids. Lipoxygenation causes the production of free radicals such as the superoxide, fatty acid, and peroxy species. Cytokinin (CK) lowers LOX and superoxide dismutase activities significantly in senescing foliage and is mimicked by the endogenous lipid antioxidant, α-tocopherol (vitamin E), in its chlorophyll-retaining and LOX-lowering effects. Further experimentation indicated that CK interaction with free radicals may occur in two ways, (i) CK may act as a direct free radical scavenger by virtue of the fact that the hydrogens of the α-carbon atom in the amine bond can be extracted, resulting in the formation of an amide: [Formula: see text][Formula: see text] (this mechanism may also, in part, explain polyamine effects), (ii) CK may serve as an incipient preventative of free radical formation by inhibiting oxidation of plant purine compounds, which at certain stages of breakdown release superoxide and hydroxyl free radicals. This effect is probably associated with a lowering of substrate affinity for xanthine oxidase. This assumption is further borne out by similar senescence-retarding effects of selective xanthine oxidase inhibitors such as allopurinol. These observations collectively indicate that prevention of free radical formation and (or) their direct scavenging should be included in the multifactorial antisencscence mode of action of cytokinin.

Modulation of Free Radical Formation by Pterin Derivatives

Pteridines ◽  
2004 ◽  
Vol 15 (3) ◽  
pp. 97-101 ◽  
Author(s):  
Oettl Karl ◽  
Joachim Greilberger ◽  
Gilbert Reibnegger
Keyword(s):  
Free Radicals ◽  
Free Radical ◽  
Biological Systems ◽  
Radical Formation ◽  
Relevant Role ◽  
Free Radical Formation

Abstract All classes of pterins, fully reduced tetrahydropterins, aromatic pterins and dihydropterins have been investigated upon their effects on radical mediated reactions. Meanwhile all these classes were shown to act as both, proand antioxidants by a number of different methods including chemical, biochemical and biological systems. From reduced pterins radicals including oxygen-, nitrogen- and pterin-radicals arc formed enzymatically and non-enzymatically, reduced pterins react with free radicals and serve as reductive agents. All classes of pterins may interfere with enzymes involved in radical formation. Upon the diversity of possibilities the net effect of a particular compound is a question of the experimental settings and the physiological relevant role often remains obscure.

scholarly journals Reactive Oxygen Species (ROS): A Review

2013 ◽  
Vol 01 (03) ◽  
pp. 152-158 ◽  
Author(s):  
Ram Rattan Gupta ◽  
Manu Gupta ◽  
Shivani Bhickta
Keyword(s):  
Biological Sciences ◽  
Reactive Oxygen Species ◽  
Free Radicals ◽  
Free Radical ◽  
Ionizing Radiation ◽  
Oxygen Toxicity ◽  
Radical Formation ◽  
Oxygen Species ◽  
Combustion Technology ◽  
Free Radical Formation

AbstractIn the late 1950's free radicals and antioxidants were almost unheard of in the clinical and biological sciences but chemists had known about them for years in the context of radiation, polymer and combustion technology. Daniel Gilbert, Rebeca Gerschman and their colleagues related the toxic effects of elevated oxygen levels on aerobes to those of ionizing radiation, and proposed that oxygen toxicity is due to free radical formation.

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