Document Detail

Regioselective cis-trans isomerization of arachidonic double bonds by thiyl radicals: the influence of phospholipid supramolecular organization.
MedLine Citation:
PMID:  14746474     Owner:  NLM     Status:  MEDLINE    
Trans unsaturated fatty acids in humans may be originated by two different contributions. The exogenous track is due to dietary supplementation of trans fats and the endogenous path deals with free-radical-catalyzed cis-trans isomerization of fatty acids. Arachidonic acid residue (5c,8c,11c,14c-20:4), which has only two out of the four double bonds deriving from the diet, was used to differentiate the two paths and to assess the importance of a radical reaction. A detailed study on the formation of trans phospholipids catalyzed by the HOCH2CH2S* radical was carried out on L-alpha-phosphatidylcholine from egg lecithin and 1-stearoyl-2-arachidonoyl-L-alpha-phosphatidylcholine (SAPC) in homogeneous solution or in large unilamellar vesicles (LUVET). Thiyl radicals were generated from the corresponding thiol by either gamma-irradiation or UV photolysis, and the reaction course was followed by GC, Ag/TLC, and 13C NMR analyses. The isomerization was found to be independent of cis double bond location (random process) in i-PrOH solution. In the case of vesicles, the supramolecular organization of lipids produced a dramatic change of the isomerization outcome: (i) in egg lecithin, the reactivity of arachidonate moieties is higher than that of oleate and linoleate residues, (ii) in the linoleate residues of egg lecithin, the 9t,12c-18:2 isomer prevailed on the 9c,12t-18:2 isomer (3:1 ratio), and (iii) a regioselective isomerization of SAPC arachidonate residues occurred in the 5 and 8 positions. This effect of "positional preference" indicates that thiyl radicals entering the hydrophobic region of the membrane bilayer start to isomerize polyunsaturated fatty acid residues having the double bonds nearest to the membrane surfaces. We propose that arachidonic acid and its trans isomers can function as biomarkers in membranes for distinguishing the two trans fatty acid-forming pathways.
Carla Ferreri; Abdelouahid Samadi; Fabio Sassatelli; Laura Landi; Chryssostomos Chatgilialoglu
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of the American Chemical Society     Volume:  126     ISSN:  0002-7863     ISO Abbreviation:  J. Am. Chem. Soc.     Publication Date:  2004 Feb 
Date Detail:
Created Date:  2004-01-28     Completed Date:  2004-05-25     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  7503056     Medline TA:  J Am Chem Soc     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1063-72     Citation Subset:  IM    
I.S.O.F., Consiglio Nazionale delle Ricerche, Via P. Gobetti 101, 40129 Bologna, Italy.
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MeSH Terms
2-Propanol / chemistry
Arachidonic Acids / chemistry*,  metabolism*
Cell Membrane / chemistry,  metabolism
Free Radicals / chemistry,  metabolism
Liposomes / chemistry
Phosphatidylcholines / chemistry,  metabolism
Phospholipids / chemistry*,  metabolism*
Substrate Specificity
Sulfhydryl Compounds / chemistry*,  metabolism*
Reg. No./Substance:
0/1-strearoyl-2-arachidonyl-sn-glycero-3-phosphatidylcholine; 0/Arachidonic Acids; 0/Free Radicals; 0/Liposomes; 0/Phosphatidylcholines; 0/Phospholipids; 0/Sulfhydryl Compounds; 67-63-0/2-Propanol

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