Determination of the alpha-tocopherol inhibition rate constant for peroxidation in low-density lipoprotein.

Culbertson SM, Antunes F, Havrilla CM, Milne GL, Porter NA
Chem Res Toxicol. 2002 15 (6): 870-6

PMID: 12067255 · DOI:10.1021/tx020012t

This work reports an estimate of the inhibition rate constant (k(inh)) for alpha-tocopherol (alpha-TOH) in low-density lipoproteins (LDL) based on cholesteryl linoleate hydroperoxide products formed during autoxidation of intact lipoproteins. The ratio of cis,trans/trans,trans product hydroperoxides was determined during the consumption of the antioxidant. For a reasonable determination of k(inh) in LDL, the pro-oxidant behavior of alpha-TOH was minimized by oxidizing LDL with an unsymmetrical amphiphilic azo initiator which significantly reduces phase-transfer mediated pro-oxidant effects of alpha-TOH. This initiator delivers a more constant flux of initiator radicals into LDL lipid regions and permits determination of alpha-TOH k(inh) in LDL. Development of a tocopherol-mediated peroxidation (TMP) model and analysis of cholesteryl linoleate hydroperoxide cis,trans/trans,trans product ratios provided an estimated value for the inhibition rate constant of alpha-TOH in a lipoprotein of k(inh) = 5.9 +/- 0.5 x 10(5) M(-)(1) s(-)(1)

MeSH Terms (15)

alpha-Tocopherol Antioxidants Free Radicals Humans Kinetics Linoleic Acid Lipid Peroxidation Lipid Peroxides Lipoproteins, LDL Liposomes Models, Chemical Oxidation-Reduction Regression Analysis Stereoisomerism Thermodynamics

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