Reactions of peroxynitrite with aldehydes as probes for the reactive intermediates responsible for biological nitration.
We have examined the reactions of peroxynitrite with short-chain aliphatic aldehydes to model the reaction of the peroxynitrite anion (ONOO-) with CO2. Aldehydes, like CO2, react rapidly with peroxynitrite and catalyze its decomposition. The pH dependence of the reaction is consistent with the addition of ONOO- (not ONOOH) to the carbonyl carbon atom of the free aldehyde forming a 1-hydroxyalkylperoxynitrite anion adduct (5), which structurally resembles the nitrosoperoxycarbonate adduct (1) formed from the reaction of ONOO- with CO2. Intermediate 5, or the secondary products derived from it, decays to give NO3- and regenerated aldehyde, with small but significant yields of H2O2, organic acids, and organic nitrates. In analogy with the peroxynitrite/CO2 system, it is suggested that 5 undergoes homolytic or heterolytic cleavage at the O-O bond, giving a caged radical pair [RCH(OH)O./ .NO2] (7) or intimate ion pair [RCH(OH)O -/+ NO2] (8). The radicals and ions in intermediates 7 and 8 can recombine within the solvent cage to form 1-hydroxyalkylnitrate [RCH(OH)ONO2] (6), which can then dissociate to give nitrate and regenerate the aldehyde. The aldehyde/ peroxynitrite adducts 5-8 mediate the oxidation of 2,2'-azinobis(3-ethylbenzthiazoline-6-sulfonate) but not the nitration of 4-hydroxyphenylacetate. The significance of these findings is discussed in relation to the mechanism(s) of the CO2-catalyzed isomerization of peroxynitrite to nitrate and biological nitrations involving peroxynitrite/CO2 adducts.
Uppu
R M
RM
Biodynamics Institute, Louisiana State University, Baton Rouge, 70803-1800, USA.
Winston
G W
GW
Pryor
W A
WA
D000079:Acetaldehyde / Q000737:chemistry* / Q000378:metabolism; D000447:Aldehydes / Q000737:chemistry* / Q000378:metabolism; D000818:Animals; D002417:Cattle; D016166:Free Radical Scavengers; D009566:Nitrates / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D016877:Oxidants / Q000737:chemistry*; D011817:Rabbits
D000447:Aldehydes; D016166:Free Radical Scavengers; D009566:Nitrates; D016877:Oxidants; C039642:peroxynitric acid; C005556:propionaldehyde; D000079:Acetaldehyde