Nitric oxide-induced oxidation of alpha-tocopherol.
Exposure of alpha-tocopherol (alpha-T) to nitric oxide under aerobic conditions resulted in a complex oxidation process whose final outcome was dictated by the nature of the reaction medium. In a cyclohexane solution, a prevailing route led to a mixture of relatively unstable polar products positive to Griess reagent. On standing at room temperature these were partially converted to the novel 2,3-dimethyl-4-acetyl-4-hydroxy-5-nitroso-2-cyclopentenone derivative. Reaction of alpha-T via a secondary oxidation path led to the formation of alpha-tocopherylquinone (alpha-TQ) as well as of little amounts of the corresponding nitrite ester. A quite different product pattern was observed when the reaction was carried out on a suspension of alpha-T in 0.1 M phosphate buffer, pH 7.4. Besides a significant formation of alpha-TQ and its nitrite ester, product analysis revealed a characteristic pattern of apolar compounds consisting of a yellow dimer and a series of related oligomers. These results provide an improved chemical background to inquire into the role of alpha-T in nitric oxide-induced tissue injury.
d'Ischia
M
M
Department of Organic and Biological Chemistry, University of Naples Federico II, Italy.
Novellino
L
L
D002021:Buffers; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D003510:Cyclohexanes; D009569:Nitric Oxide / Q000494:pharmacology*; D009599:Nitroprusside / Q000378:metabolism; D010084:Oxidation-Reduction; D010710:Phosphates; D014810:Vitamin E / Q000378:metabolism*
D002021:Buffers; D003510:Cyclohexanes; D010710:Phosphates; D014810:Vitamin E; D009599:Nitroprusside; D009569:Nitric Oxide