Isolation and characterization of addition products of α-tocopherol with peroxyl radicals of dilinoleoylphosphatidylcholine in liposomes

Hara

Murase³

et al. 2000

Lipids

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A chemiluminescence-based high-performance liquid chromatographic method was developed for the analysis of the addition products of alpha-tocopherol with phosphatidylcholine-peroxyl radicals (TOO-PC). The TOO-PC eluted from a reversed-phase column was reacted with a chemiluminescent reagent consisting of a Cypridina luciferin analog and a lipid-soluble iron chelate in acidic methanol at 50 degrees C, and the generated chemiluminescence was monitored. The detection limit for TOO-PC by this method was about 1 pmol. This method was applied to the detection of TOO-PC in the peroxidized membranes prepared from rabbit erythrocyte ghosts. When the erythrocyte ghosts were peroxidized by the addition of a water-soluble free radical initiator, a peak corresponding to TOO-PC was detected on the chromatogram with chemiluminescent detection. The amount of TOO-PC in the erythrocyte membranes increased with the depletion of endogenous alpha-tocopherol. The results indicate that this method proved useful for the detection of the TOO-PC formed by the peroxyl-radical scavenging reactions of alpha-tocopherol in biological systems.

Section: Methodsmentioning

confidence: 99%

Analysis of the addition products of α‐tocopherol with phosphatidylcholine‐peroxyl radicals by high‐performance liquid chromatography with chemiluminescent detection

Hara

Murase³

et al. 2000

Lipids

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“…Phospholipid liposomal systems have been employed to model the peroxyl-radical trapping reactions of cY-tocopherol in biological membranes (Liebler et al, 1991;Liebler & Burr, 1992;Ham & Liebler, 1995;Yamauchi et al, 1994Yamauchi et al, , 1996. The effectiveness of a-tocopherol depends not only on its ability to trap peroxyl radicals but also on the ability of the resulting a-tocopheroxyl radical to trap additional peroxyl radicals in biological membranes.…”

Section: Reaction Of A-tocopherol With Phospholipid-peroxyl Radicals mentioning

confidence: 99%

“…Therefore, products of the latter reaction may be useful markers for the antioxidative activity of a-tocopherol in biological systems. a-Tocopherol was reacted with peroxyl radicals of phosphatidylcholine at 37"C in liposomes (Yamauchi et al, 1994).…”

Section: Reaction Of A-tocopherol With Phospholipid-peroxyl Radicals mentioning

confidence: 99%

“…Each molecule of o!-tocopherol consumes thus two lipid free radicals and terminates the free-radical chain reaction. To elucidate the free-radical scavenging mechanism of tocopherols, the reaction products of tocopherols with lipid free radicals have been investigated (Winterle et al, 1984;Ham & Liebler, 1995, 1997Liebler et al, 1990Liebler et al, , 1991Liebler & Burr, 1992;Matsuo et a/, 1989;Yamauchi et al, 1989Yamauchi et al, , 1990aYamauchi et al, , 1990bYamauchi et al, , 1990cYamauchi et al, , 1993Yamauchi et al, , 1994Yamauchi et al, , 1995a). …”

mentioning

confidence: 99%

See 1 more Smart Citation

Vitamin E: Mechanism of Its Antioxidant Activity.

1997

FSTI

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The antioxidant activity of vitamin E (a-tocopherol) during the peroxidation of unsaturated lipids has been reviewed based on its reaction products. Free-radical scavenging reactions of a-tocopherol take place via the a-tocopheroxyl radical as an intermediate. If a suitable free radical is present, a non-radical product can be formed from the coupling of the free radical with the a-tocopheroxyl radical. The reaction products of a-tocopherol with lipid-peroxyl radicals are 8a-(lipid-dioxy)-a-tocopherones which are hydrolyzed to a-tocopherylquinone. If the supply of oxygen is insufficient, a-tocopherol can trap the carbon-centered radicals of lipids to form 6-0-(lipidalkyl)-a-tocopherols. On the other hand, the dimer and trimer of a-tocopherol is formed by the bimolecular self-reaction of the a-tocopheroxyl radical in a reaction mixture containing a large amount of a-tocopherol. The other product-forming pathway yields isomeric epoxy-a-tocopherylquinones and their precursors, epoxyhydroperoxy-a-tocopherones, but the mechanism of this pathway remains unknown. The reaction products of other vitamin E compounds (7-and 6-tocopherols) during lipid peroxidation are almost the same as those formed from the a-tocopherol. The tocopheroxyl radicals of 7-and 6-tocopherols prefer to react with each other to form dimeric products that are still effective as antioxidants.

“…13) Second, a-tocopherol was oxidized in phosphatidylcholine liposomes, and three products, a-tocopherylquinone (T2), 2,3-epoxy-a-tocopherylquinone (T3), and 5,6-epoxy-a-tocopherylquinone (T4), were obtained. 17,28,29) Third, the spirodiene dimer of atocopherol (T5) was synthesized following the procedure of Nelan and Robeson. 30) Fourth, a-tocopherol was left to stand in an autoxidation system of methyl linoleate under air-insu‹cient conditions.…”

Section: )mentioning

confidence: 99%

Subsequent Products After Antioxidant Actions of β-Carotene and α-Tocopherol Have NoSalmonellaMutagenicity

Sun

Bioscience, Biotechnology, and Biochemistry

Ashida

et al. 2002

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b-Carotene and a-tocopherol are important antioxidants biologically, but whether their oxidized products are toxic or not remains to be discovered. Here, we chromatographically separated 5 pure products or isomeric mixtures from reaction mixtures of b-carotene and reactive oxygens, and 17 lipid-radical scavenging products of a-tocopherol. The products were tested for mutagenicity using Salmonella typhimurium TA98, TA100, TA102, and TA104, in the presence and absence of S9. None showed mutagenicity against any of the four strains, or cytotoxicity that in‰uenced the survival of the bacteria. Lipid-peroxides have been known to increase the formation of mutagens from dietary procarcinogens such as heterocyclic amines. So, we also measured the activity to increase 3-amino-1-methyl-5 H-pyrido [4,3-b]indole (Trp-P-2) mutagenicity. The products from b-carotene and a-tocopherol did not increase, but rather several of them suppressed, the mutagenicity of Trp-P-2. Thus, the products of b-carotene and a-tocopherol formed after the antioxidant actions were not genotoxic.