Antioxidant effects of alpha- and gamma-carboxyethyl-6-hydroxychromans.
Carboxyethyl-6-hydroxychromans (CEHC), the major metabolites of both tocopherols (Toc) and tocotrienols (Toc-3), have been found in human plasma. In the present study, the antioxidant properties of alpha- and gamma-CEHC were measured and compared with alpha- and gamma- tocopherols. Following results were obtained: (1)alpha- and gamma-CEHC have the same reactivities toward radicals and exert the same antioxidant activities against lipid peroxidation in organic solution as the corresponding parent tocopherols respectively; (2) the partition coefficient decreased in the order alpha-Toc (3.36) > gamma-Toc (3.14) > alpha-CEHC (2.26) > pentamethyl-6-chromanol (1.92) > gamma-CEHC (1.83) > 0 > Trolox (-0.97); (3) alpha- and gamma-CEHC scavenge aqueous radicals more efficiently but they inhibit the lipid peroxidation within the membranes less efficiently than the corresponding alpha- and gamma-Toc, respectively; (4) alpha-CEHC inhibits the oxidation synergistically with ascorbate; and (5) alpha- and gamma-CEHC reduce Cu(II) to give Cu(I) and corresponding quinones as major product, but the prooxidant effect of CEHC in the presence of cupric ion was small. These results imply that CEHC may act as an antioxidant in vivo especially for those who take tocopherol supplement.
Yoshida
Yasukazu
Y
Human Stress Signal Research Center, National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31Midorigaoka, Ikeda, Osaka 563-8577, Japan. yoshida-ya@aist.go.jp
Niki
Etsuo
E
D000975:Antioxidants / Q000737:chemistry / Q000494:pharmacology*; D001205:Ascorbic Acid / Q000494:pharmacology; D002839:Chromans / Q000737:chemistry / Q000494:pharmacology*; D003300:Copper / Q000737:chemistry; D005609:Free Radicals / Q000737:chemistry; D008041:Linoleic Acids; D015227:Lipid Peroxidation / Q000187:drug effects; D008081:Liposomes / Q000737:chemistry; D008823:Micelles; D010084:Oxidation-Reduction; D010545:Peroxides / Q000737:chemistry; D011422:Propionates / Q000737:chemistry / Q000494:pharmacology*; D012996:Solutions; D013053:Spectrophotometry; D024505:Tocopherols / Q000737:chemistry
D000975:Antioxidants; D002839:Chromans; D005609:Free Radicals; D008041:Linoleic Acids; D008081:Liposomes; D008823:Micelles; D010545:Peroxides; D011422:Propionates; D012996:Solutions; C005575:methyl linoleate; C049375:perhydroxyl radical; D003300:Copper; D001205:Ascorbic Acid; D024505:Tocopherols