The real radical generator other than main‐product hydroperoxide in lipid autoxidation

Morita, Makio; Tokita, Masako

doi:10.1007/s11745-006-5075-9

Cited by 29 publications

(38 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Although H(P)NE was not mentioned, other interesting aldehydes, including hexanal, 2-octenal, and 2,4-decadienal, important in food technologies, received mechanistic attention. The work culminated in identification of the active components as peroxide-linked dimers containing two hydroperoxy groups (37). Their overall conclusion is that radical generation and aldehyde production are two facets of the same process, sparked by the inherent instability of the dimeric peroxyhydroperoxides.…”

Section: Involvement In the Initiation Of Lipidmentioning

confidence: 99%

Routes to 4-Hydroxynonenal: Fundamental Issues in the Mechanisms of Lipid Peroxidation

Schneider

Porter

Brash

2008

Journal of Biological Chemistry

238

205

View full text Add to dashboard Cite

Although investigation of the toxicological and physiological actions of ␣/␤-unsaturated 4-hydroxyalkenals has made great progress over the last 2 decades, understanding of the chemical mechanism of formation of 4-hydroxynonenal and related aldehydes has advanced much less. The aim of this review is to discuss mechanistic evidence for these non-enzymatic routes, especially of the underappreciated intermolecular pathways that involve dimerized and oligomerized fatty acid derivatives as key intermediates. These cross-molecular reactions of fatty acid peroxyls have also important implications for understanding of the basic initiation and propagation steps during lipid peroxidation and the nature of the products that arise.

show abstract

Section: Involvement In the Initiation Of Lipidmentioning

confidence: 99%

Routes to 4-Hydroxynonenal: Fundamental Issues in the Mechanisms of Lipid Peroxidation

Schneider

Porter

Brash

2008

Journal of Biological Chemistry

238

205

View full text Add to dashboard Cite

show abstract

“…Recently, however, Morita & Tokita (2006 reported that in methyl linoleate autoxidation the non-hydroperoxide peroxides that are responsible for the autocatalytic activity consist of two peroxide-linked linoleate moieties with two hydroperoxyl groups. Such dimer fatty acids would be prone to breakage of the cross-molecular peroxide bond and would produce, as depicted in Fig.…”

Section: Autoxidationmentioning

confidence: 99%

“…Hence, the ability of a high concentration of -tocopherol to promote hydroperoxide formation was exploited in studies I to IV. It is difficult, however, to estimate the importance of the reactions that account for the pro-oxidant properties of -tocopherol, because it is plausible, based on the recent studies on the initiation process of methyl linoleate (Morita & Tokita 2006, that unstable oligomeric peroxides are the main source of autocatalytic radicals also in the autoxidation of CLA methyl esters.…”

Section: Role Of -Tocopherol (I To Iv)mentioning

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

“…In our previous paper [6], the lack of autocatalytic activity was also clearly showed by using a highly rigorous and sensitive detecting method when the purified main-product hydroperoxide of methyl linoleate was examined under the usual storage conditions and at body temperature; in addition, a type of substance revealing potent autocatalytic activity was found in autoxidizing methyl linoleate.…”

Section: Introductionmentioning

confidence: 92%

“…Scheme 1 We assumed [6] that the mechanism of their homolytic decomposition and radical supply is an energetically favorable concerted one as depicted also in Scheme 1. The mechanism predicted the formation of hydroxy radicals and hexanal as direct products of the homolysis, and the formation of 2,4-decadienal via the b-scission route from linoleate-skeleton alkoxy radicals.…”

Section: Introductionmentioning

confidence: 99%

Hydroxy Radical, Hexanal, and Decadienal Generation by Autocatalysts in Autoxidation of Linoleate Alone and with Eleostearate

Morita

Tokita

2008

Lipids

Self Cite

View full text Add to dashboard Cite

The formation of hydroxy radicals, hexanal, and 2,4-decadienal was demonstrated from the autocatalytic dimer peroxide which had been reported by us in autoxidizing linoleate (Morita and Tokita in Lipids 41:91-95, 2006). Then, autoxidizing linoleate containing eleostearate was investigated for new autocatalytic substances. The substances obtained were identified as peroxide-linked polymers consisting of both linoleate- and eleostearate-origin units with one hydroperoxy group, and also revealed activity of hydroxy-radical generation. The background of this study is as follows: the above paper reported this autocatalytic dimer peroxide as one of the real radical generators in linoleate autoxidation; this is a peroxide-linked dimer consisting of two linoleate moieties with two hydroperoxy groups, and was much more important than the main-product hydroperoxide in autocatalytic radical supply; its proposed decomposition mechanism has suggested the generation of hydroxy radicals, hexanal, and 2,4-decadienal; on the other hand, analogy to the formation mechanism of this dimer peroxide has predicted the formation of similar polymeric products from conjugated polyene components in lipids. In this study, these two predictions were successfully verified and a discussion is presented in connection with them.

show abstract

The real radical generator other than main‐product hydroperoxide in lipid autoxidation

Cited by 29 publications

References 14 publications

Routes to 4-Hydroxynonenal: Fundamental Issues in the Mechanisms of Lipid Peroxidation

Routes to 4-Hydroxynonenal: Fundamental Issues in the Mechanisms of Lipid Peroxidation

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

Hydroxy Radical, Hexanal, and Decadienal Generation by Autocatalysts in Autoxidation of Linoleate Alone and with Eleostearate

Contact Info

Product

Resources

About