Gamma-tocopherol detoxification of nitrogen dioxide: superiority to alpha-tocopherol.
In the vitamin E group, alpha-tocopherol is generally considered to be the most potent antioxidant with the highest vitamin bioactivity, yet gamma-tocopherol is produced in greater amounts by many plants and is the principal tocopherol in the United States diet. This report describes a fundamental difference in the chemical reactivities of alpha-tocopherol and gamma-tocopherol with nitrogen dioxide (NO2), which leads to the formation of a nitrosating agent from alpha-tocopherol, but not from gamma-tocopherol. Nitric oxide (NO) is a major product of the reaction of gamma-tocopherol with NO2, while alpha-tocopherol reacts with NO2 to form an intermediate tocopheroxide analogue. The biological significance of gamma-tocopherol is suggested by limited epidemiological data as well as the observation that it is a more potent inhibitor than alpha-tocopherol of neoplastic transformation during the postinitiation phase in 3-methylcholanthrene-treated C3H/10T1/2 murine fibroblasts. This latter property suggests the superiority of gamma-tocopherol in a mammalian biological assay and a role for endogenous NO production in promotion of neoplastic transformation.
Cooney
R V
RV
Cancer Research Center of Hawaii, University of Hawaii, Honolulu 96813.
Franke
A A
AA
Harwood
P J
PJ
Hatch-Pigott
V
V
Custer
L J
LJ
Mordan
L J
LJ
D000818:Animals; D000975:Antioxidants; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D066298:In Vitro Techniques; D051379:Mice; D009569:Nitric Oxide / Q000737:chemistry; D009585:Nitrogen Dioxide / Q000737:chemistry*; D014810:Vitamin E / Q000737:chemistry*
D000975:Antioxidants; D014810:Vitamin E; D009569:Nitric Oxide; D009585:Nitrogen Dioxide