Mechanisms of action and reactivities of the free radicals of inhibitors

Denisov, Evgeniy T.; Khudyakov, I. V.

doi:10.1021/cr00082a003

Cited by 287 publications

(195 citation statements)

References 56 publications

Supporting

Mentioning

193

Contrasting

Order By: Relevance

“…The significance of this reaction may be anticipated to be greater in metal-catalysed autoxidations because alkoxyl radicals are formed through homolytic cleavage of hydroperoxides. Autoxidation is defined as a chain reaction if the chain termination steps are slower than the chain propagation steps (Denisov & Khudyakov 1987).…”

Section: Figurementioning

confidence: 99%

Autoxidation of Conjugated Linoleic Acid Methyl Ester in the Presence of α‐Tocopherol: The Hydroperoxide Pathway

Pajunen

Johansson

Hase

et al. 2008

Lipids

View full text Add to dashboard Cite

The autoxidation of conjugated linoleic acid (CLA) is poorly understood in spite of increasing interest in the beneficial biological properties of CLA and growing consumption of CLA-rich foods. In this thesis, the autoxidation reactions of the two major CLA isomers, 9-cis,11-transoctadecadienoic acid and 10-trans,12-cis-octadecadienoic acid, are investigated. The results contribute to an understanding of the early stages of the autoxidation of CLA methyl ester, and provide for the first time a means of producing and separating intact CLA methyl ester hydroperoxides as well as basic knowledge on lipid hydroperoxides and their hydroxy derivatives.Conjugated diene allylic monohydroperoxides were discovered as primary autoxidation products formed during autoxidation of CLA methyl esters in the presence and absence oftocopherol. This established that one of the autoxidation pathways of CLA methyl ester is the hydroperoxide pathway.Hydroperoxides were produced from the two major CLA methyl esters by taking advantage of the effect of -tocopherol to promote hydroperoxide formation. The hydroperoxides were analysed and separated first as methyl hydroxyoctadecadienoates and then as intact hydroperoxides by HPLC. The isolated products were characterized by UV, GC-MS, and NMR techniques. In the presence of a high amount of -tocopherol, the autoxidation of CLA methyl ester yields six kinetically-controlled conjugated diene monohydroperoxides and is diastereoselective in favour of one particular geometric isomer as a pair of enantiomers. The primary autoxidation products produced from the two major CLA isomers include new positional isomers of conjugated diene monohydroperoxides, the 8-, 10-, 12-, and 14-hydroperoxyoctadecadienoates. Furthermore, two of these new positional isomers have an unusual structure for a cis,trans lipid hydroperoxide where the allylic methine carbon is adjacent to the cis instead of the usual trans double bond.The 1 H and 13 C NMR spectra of nine isomeric methyl hydroxyoctadecadienoates and of ten isomeric methyl hydroperoxyoctadecadienoates including the unusual cis,trans hydroperoxides, i.e. Me 8-OOH-9c,11t and Me 14-OOH-10t,12c, were fully assigned with the aid of 2D NMR spectroscopy. The assigned NMR data enabled determination of the effects of the hydroxyl and hydroperoxyl groups on the carbon chemical shifts of CLA isomers, identification of diagnostic signals, and determination of chemical shift differences of the olefinic resonances that may help with the assignment of structure to as yet unknown lipid hydroperoxides either as hydroxy derivatives or as intact hydroperoxides.A mechanism for the hydroperoxide pathway of CLA autoxidation in the presence of a high amount of -tocopherol was proposed based on the characterized primary products, their relative distribution, and theoretical calculations. This is an important step forward in CLA research, where exact mechanisms for the autoxidation of CLA have not been presented before. Knowledge of these hydroperoxide formation steps is of cr...

show abstract

Section: Figurementioning

confidence: 99%

Autoxidation of Conjugated Linoleic Acid Methyl Ester in the Presence of α‐Tocopherol: The Hydroperoxide Pathway

Pajunen

Johansson

Hase

et al. 2008

Lipids

View full text Add to dashboard Cite

show abstract

“…These findings indicated that these compounds, in parallel with the reaction with hydroperoxides, were also destroyed by direct oxidation. Denisov and Khudyakov (1987) If it does not participate in the chain propagation, the dependence (III) is valid:…”

Section: Resultsmentioning

confidence: 99%

“…The introduction of an antioxidant (inhibitor -InH) into the oxidising lipid system leads to a change in the mechanism of the process and, as a result, in the process kinetics. The effect of the inhibitor depends on the participation of its molecule and the radicals formed from the latter in a series of reactions (Denisov & Khudyakov 1987).…”

Section: Preparation Of Amidesmentioning

confidence: 99%

Antioxidant activity and mechanism of action of some synthesised phenolic acid amides of aromatic amines

Marinova¹,

Georgiev²,

Totseva³

et al. 2013

Czech J. Food Sci.

View full text Add to dashboard Cite

Marinova E., Georgiev L., Totseva I., Seizova K., Milkova T. (2013): Antioxidant activity and mechanism of action of some synthesised phenolic acid amides of aromatic amines. Czech J. Food Sci., 31: 5-13.The antioxidative activities and mechanism of action were studied of eight synthesised cinnamoyl-and hydroxycinnamoyl amides of biogenic amines (caffeoyldopamine, cinnamoyldopamine, p-coumaroyldopamine, feruloyldopamine, sinapoyldopamine, caffeoylphenylethylamine, caffeoyltyramine, and caffeoyltryptamine) in a wide concentration range (2.5-20 × 10 -4 M) during autoxidation of triacylglycerols of sunflower oil. It was established that all amides exhibited excellent antioxidant activity, higher than or comparable with that of caffeic acid. The best activity was shown by caffeoyldopamine followed by cinnamoyldopamine and caffeoyltyramine. The analysis of the kinetic data obtained showed that the presence of hydroxyl groups in the amino part (derivatives of dopamine and tyramine) led to direct oxidation of the molecules during the process and stabilisation of the resulting radicals. In contrast, the amides without hydroxyl groups in the amino part participated in the side reaction with peroxides and the resulting radicals took part in one side reaction of the chain propagation as did caffeic acid.

show abstract

“…[14,26] The colour of the reaction solutions deepened with more dark precipitates generated at higher Fe 3þ concentrations. Fig.…”

Section: Resultsmentioning

confidence: 99%

Photochlorination of aniline in Fe3+-containing saline water under simulated solar light irradiation

2012

Environ. Chem.

View full text Add to dashboard Cite

Environmental context. Aromatic amines are widely used chemicals, which show enhanced toxicity and longer environmental persistence when halogenated. We investigated the chlorination of aniline in seawater and in natural aqueous solutions containing Fe 3þ and Cl À , under simulated sunlight irradiation. The results increase our understanding of the transformation pathway of typical nitrogen-containing aromatic contaminants in the environment.Abstract. Photochlorination of aniline was observed in aqueous solutions containing dissolved Fe III and chloride ions under simulated solar light irradiation. Effects of O 2 , Cl À , Fe 3þ and pH on the formation of chloroanilines (CAs) were investigated. para-chloroaniline (4CA) was identified as the main chlorinated product. The formation of 4CA is enhanced with increased concentrations of Cl À or Fe 3þ , and decreased pH, whereas oxygen plays a negligible role in the process. The results indicate that, Cl is formed mainly by the photodissociation of FeCl 2þ -FeCl 2 þ complexes, and reacts with Cl À to produce Cl 2 À . Aniline is then oxidised by Cl 2 À into an anilino radical cation, which further reacts with Cl 2 À to generate CAs. The photochlorination of aniline in natural seawater was also observed. Other phototransformation products of aniline were detected and a transformation pathway was proposed. This work provides evidence for the photochemical chlorination path of aniline-based aromatic amines in aqueous solutions.

show abstract

Mechanisms of action and reactivities of the free radicals of inhibitors

Cited by 287 publications

References 56 publications

Autoxidation of Conjugated Linoleic Acid Methyl Ester in the Presence of α‐Tocopherol: The Hydroperoxide Pathway

Autoxidation of Conjugated Linoleic Acid Methyl Ester in the Presence of α‐Tocopherol: The Hydroperoxide Pathway

Antioxidant activity and mechanism of action of some synthesised phenolic acid amides of aromatic amines

Photochlorination of aniline in Fe3+-containing saline water under simulated solar light irradiation

Contact Info

Product

Resources

About