Effect of catechin O-methylated metabolites and analogues on human LDL oxidation.
The effects of catechin metabolites and methylated analogues on LDL oxidation were studied in vitro using either a water-soluble initiator or copper ions to induce lipid peroxidation. Direct addition of catechin O-methylated analogues to the oxidation mixture led to a clear protective effect during lag phase and for the metabolites during both lag and propagation phases. The structure-activity relationships obtained with these selectively O-methylated compounds allowed determination of catechin active moietie: the catechol B-ring. Based on physical chemical studies, these results suggest that the mechanism implied in the scavenging properties of flavan-3-ols is not only hydrogen transfer, as generally described, but mainly an electronic transfer from the phenolate, and that 3'- and 4'-O-methylcatechin seem, moreover, to act as amphiphilic chain-breaking antioxidants. However, the plasma concentration of flavan-3-ols necessary to protect LDL is far greater than those usually found in human plasma. Therefore, the data do not support a direct physiological relevance of flavan-3-ols as antioxidants in lipid processes. Future research should focus on other effects besides simple antioxidant ones.
Cren-Olivé
Cécile
C
Chimie Organique et Macromoléculaire, Université des Sciences et Technologies de Lille, UMR CNRS 8009, Villeneuve d'Ascq, France.
Teissier
Elisabeth
E
Duriez
Patrick
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Rolando
Christian
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D000975:Antioxidants / Q000378:metabolism; D002392:Catechin / Q000737:chemistry* / Q000494:pharmacology*; D003300:Copper / Q000737:chemistry; D005609:Free Radicals; D006801:Humans; D050356:Lipid Metabolism; D015227:Lipid Peroxidation; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008956:Models, Chemical; D010100:Oxygen / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013997:Time Factors
D000975:Antioxidants; D005609:Free Radicals; D008077:Lipoproteins, LDL; D003300:Copper; D002392:Catechin; D010100:Oxygen