Antioxidant effects of α‐ and γ‐carboxyethyl‐6‐hydroxychromans

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Abstract
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 α- and γ-CEHC were measured and compared with α- and γ- tocopherols. Following results were obtained: (1)α- and γ-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 α-Toc (3.36) > γ-Toc (3.14) > α-CEHC (2.26) > pentamethyl-6-chromanol (1.92) > γ-CEHC (1.83) > 0 > Trolox (-0.97); (3) α- and γ-CEHC scavenge aqueous radicals more efficiently but they inhibit the lipid peroxidation within the membranes less efficiently than the corresponding α- and γ-Toc, respectively; (4) α-CEHC inhibits the oxidation synergistically with ascorbate; and (5) α- andγ-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.

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