Reactions of peroxynitrite with gamma-tocopherol.
The reaction of peroxynitrite with gamma-tocopherol (gamma-TH) in a methanol/potassium phosphate buffer solution results in the formation of four major products, which were identified as 2,7,8-trimethyl-2-(4,8,12-trimethyldecyl)-5-nitro-6-chromanol++ + (NGT), 2,7,8-trimethyl-2-(4,8,12-trimethyldecyl)-5,6-chromaquinone (tocored), and two diastereomers of 8a-(hydroxy)-gamma-tocopherone. NGT was the major product formed in these reactions, and its formation was modestly increased by increasing amounts of Fe(3+)-EDTA. Tocored and NGT also were formed when gamma-TH was exposed to 3-morpholinosydnonimine (SIN-1), a compound that decomposes to form peroxynitrite. When gamma-TH reacted with the nitrating agent NO2+BF4- in acetonitrile or methanol/potassium phosphate buffer, NGT and tocored also were formed, but the major product detected was gamma-tocopherol quinone (gamma-TQ). This product was not detected in reactions involving peroxynitrite. Oxidation of gamma-TH by peroxynitrite involves nitration and electron transfer reactions. Since the product distribution in oxidations with NO2+BF4- differed substantially from that in oxidations with peroxynitrite and SIN-1, NO2+ appeared not to be the principal species involved in NGT formation. Nitration of gamma-TH may involve either peroxynitrite or some peroxynitrite-derived oxidant other than NO2+. Because of its stability and formation as a novel product of the reaction between gamma-TH with peroxynitrite, NGT may be a useful in vivo marker for peroxynitrite interactions with lipid structures that contain gamma-TH.
Hoglen
N C
NC
Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson 85721-0207, USA. hoglen@tonic.pharm.arizona.edu
Waller
S C
SC
Sipes
I G
IG
Liebler
D C
DC
D009682:Magnetic Resonance Spectroscopy; D008981:Molsidomine / Q000031:analogs & derivatives / Q000737:chemistry; D009566:Nitrates / Q000737:chemistry*; D010084:Oxidation-Reduction; D013056:Spectrophotometry, Ultraviolet; D014810:Vitamin E / Q000737:chemistry*
D009566:Nitrates; D014810:Vitamin E; C039642:peroxynitric acid; C002385:linsidomine; D008981:Molsidomine