Autoxidation and antioxidant activity of ubiquinol homologues in large unilamellar vesicles.
The antioxidant activity of ubiquinol homologues with different side-chain length such as ubiquinol-3 and ubiquinol-7 was compared with that of alpha-tocopherol when peroxidation was induced by the water-soluble initiator 2,2'-azobis-(2-amidinopropane hydrochloride). In large unilamellar vesicles containing equal amounts of alpha-tocopherol, ubiquinol-3 and ubiquinol-7 the rates of inhibition were very similar but the stoichiometric factor of quinols was approximately 1. To explain this low value, which is one-half of that found when the autoxidation was performed in apolar solvents (Chem. Phys. Lipids (1992) 61, 121-130), the oxidation of alpha-tocopherol and ubiquinol-3 initiated by the azocompound was studied both in methanol and in dimiristoyl-lecithin vesicles. The results obtained show that the ubiquinol homologues undergo a radical chain reaction taking place at the polar interface and suggest that the average preferred location of both quinol headgroups is near to the outer surface of the bilayer.
Cipollone
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Dipartimento di Biochimica G. Moruzzi, Università degli Studi di Bologna, Italy.
Fiorentini
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D
Galli
M C
MC
Sechi
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AM
Landi
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L
D000975:Antioxidants / Q000737:chemistry*; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D066298:In Vitro Techniques; D007700:Kinetics; D008051:Lipid Bilayers / Q000737:chemistry*; D010084:Oxidation-Reduction; D010713:Phosphatidylcholines / Q000737:chemistry; D014451:Ubiquinone / Q000031:analogs & derivatives* / Q000737:chemistry; D014810:Vitamin E / Q000737:chemistry
D000975:Antioxidants; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D014451:Ubiquinone; D014810:Vitamin E; C003741:ubiquinol