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Original

LC/ESR/MS study of spin trapped carbon-centred radicals formed from in vitro lipoxygenase-catalysed peroxidation of γ-linolenic acid

, , & , PhD
Pages 442-455 | Received 05 Dec 2007, Published online: 07 Jul 2009
 

Abstract

γ-Linolenic acid (GLA) has been reported as a potential anti-cancer and anti-inflammatory agent and has received substantial attention in cancer care research. One of the many proposed mechanisms for GLA biological activity is free radical-mediated lipid peroxidation. However, no direct evidence has been obtained for the formation of GLA-derived radicals. In this study, a combination of LC/ESR and LC/MS was used with α-[4-pyridyl-1-oxide]-N-tert-butyl nitrone (POBN) to profile the carbon-centred radicals that are generated in lipoxygenase-catalysed GLA peroxidation. A total of four classes of GLA-derived radicals were characterized including GLA-alkyl, epoxyallylic, dihydroxyallylic radicals and a variety of carbon-centred radicals stemming from the β-scissions of GLA-alkoxyl radicals. By means of an internal standard in LC/MS, one also quantified each radical adduct in all its redox forms, including an ESR-active form and two ESR-silent forms. The results provided a good starting point for ongoing research in defining the possible biological effects of radicals generated from GLA peroxidation.

Abbreviations
ACN=

acetonitrile

EIC=

extracted ion chromatography

ESR=

electron spin resonance

GLA=

gamma linolenic acid (all-cis-6, 9, 12-octadecatrienoic acid)

HOAc=

glacial acetic acid

HPLC (LC)=

high performance liquid chromatography

I.S.=

internal standard

LA=

linoleic acid (cis, cis-9, 12-octadecadienoic acid)

LOX=

lipoxygenase

L=

lipid alkyl radicals

L(OH)2=

lipid dihydroxyallylic radicals

MRM=

multiple reaction monitoring

OL=

lipid epoxyallylic radicals

POBN=

α-[4-pyridyl-1-oxide]-N-tert-butyl nitrone

PUFAs=

polyunsaturated fatty acids

TIC=

total ion current

tR=

retention time.

Abbreviations
ACN=

acetonitrile

EIC=

extracted ion chromatography

ESR=

electron spin resonance

GLA=

gamma linolenic acid (all-cis-6, 9, 12-octadecatrienoic acid)

HOAc=

glacial acetic acid

HPLC (LC)=

high performance liquid chromatography

I.S.=

internal standard

LA=

linoleic acid (cis, cis-9, 12-octadecadienoic acid)

LOX=

lipoxygenase

L=

lipid alkyl radicals

L(OH)2=

lipid dihydroxyallylic radicals

MRM=

multiple reaction monitoring

OL=

lipid epoxyallylic radicals

POBN=

α-[4-pyridyl-1-oxide]-N-tert-butyl nitrone

PUFAs=

polyunsaturated fatty acids

TIC=

total ion current

tR=

retention time.

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