Spin-trapping in early and some recent nitroso chemistry

1982 ◽  
Vol 60 (12) ◽  
pp. 1602-1609 ◽  
Author(s):  
Th. J de Boer
Keyword(s):  
Radical Reaction ◽  
Radical Scavenging ◽  
Esr Spectra ◽  
Spin Trapping ◽  
Nitroso Compounds ◽  
Organic Radical ◽  
Organometallic Reagents ◽  
Alkyl Nitrites ◽  
Radical Scavenging Properties ◽  
High Yields

The radical scavenging properties of nitroso compounds were discovered accidentally during investigations of photochemical nitrosation of hydrocarbons with alkyl nitrites. Depending on the nature of substrates and nitrosating agent, various nitroxides can be generated. Identification of these nitroxides by their esr spectra has triggered the development of the spin-trapping technique which has been useful in the elucidation of many organic radical reaction mechanisms. Recent studies have shown that the behavior of nitrosocyclopropanes and α-chloro-nitroso alkanes is unorthodox upon irradiation. Dark reactions of α-chloro-nitroso alkanes with Grignard reagents lead to nitrones by a polar mechanism and to oximes by electron transfer. In the latter case high yields of hydrocarbon dimers are sometimes obtained from the Grignard and other organometallic reagents, despite the presence of nitroso compounds. In the postulated reaction mechanism dimers and higher associates from the organometallic reagent play an essential role.

Spin trapping by use of nitrosodurene and its derivatives

1982 ◽  
Vol 60 (12) ◽  
pp. 1532-1541 ◽  
Author(s):  
Ryusei Konaka ◽  
Shigeru Terabe ◽  
Taiichi Mizuta ◽  
Shigeru Sakata
Keyword(s):  
Hydrogen Peroxide ◽  
Esr Spectra ◽  
Spin Trapping ◽  
Nitroso Compounds ◽  
Spin Adduct ◽  
Spin Traps ◽  
Spectral Pattern ◽  
Alkyl Radicals ◽  
Alkyl Hydroperoxides ◽  
Tert Butyl Hydroperoxide

In spin trapping the N-methyl-N-phenylaminomethyl radical with nitrosodurene, an esr spectmm exhibiting line width alternation was observed despite the normal spectral pattern found with the use of nitroso-tert-butane. Nitrosodurene derivatives, N-duryl nitrone and methyl N-duryl nitrone, have been revealed to be other excellent spin traps for the N-, 0-, and S-centered radicals. Spin adducts of these radicals, which can be independently prepared by spin trapping with nitrosodurene, are stable and can be easily discriminated by large differences in β-hydrogen splittings or characteristic patterns. Methyl N-duryl nitrone reacted with tert-butyl hydroperoxide to give a spin adduct which could be clearly distinguished in the esr spectra from the tert-butoxy adducts prepared independently from other sources. Accordingly, it seems to be the tert-butylperoxy adduct. Similarly, hydrogen peroxide gave a different spectrum from the hydroxy adducts. Alkyl hydroperoxides caused molecule-induced homolysis with the nitroso compounds to produce alkoxy adducts of the respective nitroso compounds. Some phenyl and duryl alkoxy nitroxides undergo decomposition to give alkyl radicals which were trapped by the nitroso compounds.

Alkoxy radical intermediates in the thermal and photochemical oxidation of alcohols

1973 ◽  
Vol 332 (1589) ◽  
pp. 151-166 ◽  
Keyword(s):  
Uranyl Nitrate ◽  
Radical Scavenging ◽  
Lead Tetraacetate ◽  
Photochemical Oxidation ◽  
Nitroso Compounds ◽  
Alkoxy Radical ◽  
Alkoxy Radicals ◽  
Radical Intermediates ◽  
Alkyl Nitrites ◽  
Oxidation Of Alcohols

Radical scavenging by nitrone and nitroso compounds, used in conjunction with e. s. r. spectroscopy, has demonstrated that alkoxy radicals are important intermediates during the thermal and photochemical oxidation of primary and secondary aliphatic alcohols: R 1 R 2 CHOH+X(ox) → R 1 R 2 CHȮH + + X(red) R 1 R 2 CHȮH + +R 1 R 2 CHOH → R 1 R 2 CHO. + R 1 R 2 CHOH + 2 R 1 R 2 CHO. + PhCH ═ NBu t → R 1 R 2 CHO─CHPh─.O─NBu t ─R 1 R 2 CHoH→R 1 R 2 C─OH + Bu t N ═ O → R 1 R 2 C─N─Bu t ─OH─O. Oxidants include the herbicidal paraquat ion, peroxydisulphate ion, the peroxydisulphatesilver (ɪ) couple, lead tetraacetate and uranyl nitrate. Independet generation of alkoxy radicals (photolysis of the corresponding alkyl nitrites R 1 R 2 CHONO) and their hydroxyalkyl isomers (H abstraction from the parent alcohol) confirms the e. s. r. assignments: mechanistic consequences of the results are discussed.

Spin trapping of the azide radical with nitroso compounds

1982 ◽  
Vol 60 (12) ◽  
pp. 1597-1597 ◽  
Author(s):  
Walter Kremers ◽  
Grant W Koroll ◽  
Ajit Singh
Keyword(s):  
Electron Spin Resonance ◽  
Aqueous Solutions ◽  
Hydroxyl Radicals ◽  
Electron Spin ◽  
Esr Spectra ◽  
Spin Trapping ◽  
Nitroso Compounds ◽  
Spin Traps ◽  
Spin Resonance

Azide radicals (N3·) are formed in aqueous solutions by the reaction of hydroxyl radicals (·OH) with azide anions (N3aq−). Azide radicals have been spin trapped with three nitroso spin traps: nitrosodurene (ND), 2,6-dideutero-3,5-dibromo-4-nitrosobenzene sulfonate (DDNBS), and 2-methyl-2-nitrosopropane (MNP). The electron spin resonance (esr) spectra show the presence of two molecules of the spin traps in the spin-trapped species.

The Mechanisms Behind the Biological Activity of Flavonoids

2019 ◽  
Vol 26 (39) ◽  
pp. 6976-6990 ◽  
Author(s):  
Ana María González-Paramás ◽  
Begoña Ayuda-Durán ◽  
Sofía Martínez ◽  
Susana González-Manzano ◽  
Celestino Santos-Buelga
Keyword(s):  
Gene Expression ◽  
Biological Activity ◽  
Phenolic Compounds ◽  
Intracellular Signaling ◽  
Molecular Mechanisms ◽  
Radical Scavenging ◽  
Model Organism ◽  
Stress Theory ◽  
Radical Scavenging Properties

: Flavonoids are phenolic compounds widely distributed in the human diet. Their intake has been associated with a decreased risk of different diseases such as cancer, immune dysfunction or coronary heart disease. However, the knowledge about the mechanisms behind their in vivo activity is limited and still under discussion. For years, their bioactivity was associated with the direct antioxidant and radical scavenging properties of phenolic compounds, but nowadays this assumption is unlikely to explain their putative health effects, or at least to be the only explanation for them. New hypotheses about possible mechanisms have been postulated, including the influence of the interaction of polyphenols and gut microbiota and also the possibility that flavonoids or their metabolites could modify gene expression or act as potential modulators of intracellular signaling cascades. This paper reviews all these topics, from the classical view as antioxidants in the context of the Oxidative Stress theory to the most recent tendencies related with the modulation of redox signaling pathways, modification of gene expression or interactions with the intestinal microbiota. The use of C. elegans as a model organism for the study of the molecular mechanisms involved in biological activity of flavonoids is also discussed.

scholarly journals Chemical Constituents of the Essential Oil from Ecuadorian Endemic Species Croton ferrugineus and Its Antimicrobial, Antioxidant and α-Glucosidase Inhibitory Activity

Molecules ◽  
2021 ◽  
Vol 26 (15) ◽  
pp. 4608
Author(s):  
Eduardo Valarezo ◽  
Génesis Gaona-Granda ◽  
Vladimir Morocho ◽  
Luis Cartuche ◽  
James Calva ◽  
...  
Keyword(s):  
Gas Chromatography ◽  
Essential Oil ◽  
Endemic Species ◽  
Chemical Constituents ◽  
Radical Scavenging ◽  
Moderate Activity ◽  
Gram Positive Bacteria ◽  
Flame Ionization ◽  
Total Composition ◽  
Radical Scavenging Properties

Croton ferrugineus Kunth is an endemic species of Ecuador used in traditional medicine both for wound healing and as an antiseptic. In this study, fresh Croton ferrugineus leaves were collected and subjected to hydrodistillation for extraction of the essential oil. The chemical composition of the essential oil was determined by gas chromatography equipped with a flame ionization detector and gas chromatography coupled to a mass spectrometer using a non-polar and a polar chromatographic column. The antibacterial activity was assayed against three Gram-positive bacteria, one Gram-negative bacterium and one dermatophyte fungus. The radical scavenging properties of the essential oil was evaluated by means of DPPH and ABTS assays. The chemical analysis allowed us to identify thirty-five compounds representing more than 99.95% of the total composition. Aliphatic sesquiterpene hydrocarbon trans-caryophyllene was the main constituent with 20.47 ± 1.25%. Other main compounds were myrcene (11.47 ± 1.56%), β-phellandrene (10.55 ± 0.02%), germacrene D (7.60 ± 0.60%), and α-humulene (5.49 ± 0.38%). The essential oil from Croton ferrugineus presented moderate activity against Candida albicans (ATCC 10231) with an MIC of 1000 μg/mL, a scavenging capacity SC50 of 901 ± 20 µg/mL with the ABTS method, and very strong antiglucosidase activity with an IC50 of 146 ± 20 µg/mL.

scholarly journals Chemical Analysis, Toxicity Study, and Free-Radical Scavenging and Iron-Binding Assays Involving Coffee (Coffea arabica) Extracts

Molecules ◽  
2021 ◽  
Vol 26 (14) ◽  
pp. 4169
Author(s):  
Nuntouchaporn Hutachok ◽  
Pimpisid Koonyosying ◽  
Tanachai Pankasemsuk ◽  
Pongsak Angkasith ◽  
Chaiwat Chumpun ◽  
...  
Keyword(s):  
Free Radical ◽  
Mononuclear Cells ◽  
Radical Scavenging ◽  
Free Radical Scavenging ◽  
Chemical Compositions ◽  
Coffee Bean ◽  
Dependent Manner ◽  
Roasted Coffee ◽  
Instant Coffee ◽  
Radical Scavenging Properties

We aimed to analyze the chemical compositions in Arabica coffee bean extracts, assess the relevant antioxidant and iron-chelating activities in coffee extracts and instant coffee, and evaluate the toxicity in roasted coffee. Coffee beans were extracted using boiling, drip-filtered and espresso brewing methods. Certain phenolics were investigated including trigonelline, caffeic acid and their derivatives, gallic acid, epicatechin, chlorogenic acid (CGA) and their derivatives, p-coumaroylquinic acid, p-coumaroyl glucoside, the rutin and syringic acid that exist in green and roasted coffee extracts, along with dimethoxycinnamic acid, caffeoylarbutin and cymaroside that may be present in green coffee bean extracts. Different phytochemicals were also detected in all of the coffee extracts. Roasted coffee extracts and instant coffees exhibited free-radical scavenging properties in a dose-dependent manner, for which drip coffee was observed to be the most effective (p < 0.05). All coffee extracts, instant coffee varieties and CGA could effectively bind ferric ion in a concentration-dependent manner resulting in an iron-bound complex. Roasted coffee extracts were neither toxic to normal mononuclear cells nor breast cancer cells. The findings indicate that phenolics, particularly CGA, could effectively contribute to the iron-chelating and free-radical scavenging properties observed in coffee brews. Thus, coffee may possess high pharmacological value and could be utilized as a health beverage.

scholarly journals Melatonin in Wine and Beer: Beneficial Effects

Molecules ◽  
2021 ◽  
Vol 26 (2) ◽  
pp. 343
Author(s):  
Javier Marhuenda ◽  
Débora Villaño ◽  
Raúl Arcusa ◽  
Pilar Zafrilla
Keyword(s):  
Intracellular Signaling ◽  
Plasma Concentrations ◽  
Radical Scavenging ◽  
Direct Interaction ◽  
Melatonin Receptors ◽  
Current Evidence ◽  
Sleep Cycle ◽  
Beneficial Effects ◽  
Neuroprotective Actions ◽  
Radical Scavenging Properties

Melatonin is a hormone secreted in the pineal gland with several functions, especially regulation of circadian sleep cycle and the biological processes related to it. This review evaluates the bioavailability of melatonin and resulting metabolites, the presence of melatonin in wine and beer and factors that influence it, and finally the different benefits related to treatment with melatonin. When administered orally, melatonin is mainly absorbed in the rectum and the ileum; it has a half-life of about 0.45–1 h and is extensively inactivated in the liver by phase 2 enzymes. Melatonin (MEL) concentration varies from picograms to ng/mL in fermented beverages such as wine and beer, depending on the fermentation process. These low quantities, within a dietary intake, are enough to reach significant plasma concentrations of melatonin, and are thus able to exert beneficial effects. Melatonin has demonstrated antioxidant, anticarcinogenic, immunomodulatory and neuroprotective actions. These benefits are related to its free radical scavenging properties as well and the direct interaction with melatonin receptors, which are involved in complex intracellular signaling pathways, including inhibition of angiogenesis and cell proliferation, among others. In the present review, the current evidence on the effects of melatonin on different pathophysiological conditions is also discussed.

Free radical scavenging properties and phenolic characterization of some edible plants

2009 ◽  
Vol 114 (1) ◽  
pp. 276-281 ◽  
Author(s):  
Ilkay Orhan ◽  
Murat Kartal ◽  
Mahmoud Abu-Asaker ◽  
F. Sezer Şenol ◽  
Gülderen Yilmaz ◽  
...  
Keyword(s):  
Free Radical ◽  
Radical Scavenging ◽  
Free Radical Scavenging ◽  
Edible Plants ◽  
Radical Scavenging Properties

The formation and radical scavenging properties of ethylenediaminetetra-acetic acid N,N′-dioxide in aqueous m-chloroperbenzoic acid

1986 ◽  
Vol 0 (13) ◽  
pp. 987-987 ◽  
Author(s):  
D. Martin Davies ◽  
David Dunn ◽  
Mohammad Haydarali ◽  
Roland M. Jones ◽  
J. Mark Lawther
Keyword(s):  
Acetic Acid ◽  
Radical Scavenging ◽  
Radical Scavenging Properties
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