The reaction of alkylnitronates with glutathione

Nitroalkanes are agents of occupational importance, and 2-nitropropane has been shown to be mutagenic and hepatotoxic. Here the reaction of alkylnitronates, such as propyl-2-nitronate, with glutathione and other thiol nucleophiles has been studied by using TLC, HPLC, and spectroscopic methods. Propyl-2-nitronate, but not 2-nitropropane, reacted with glutathione in acidic media. The reaction yielded an inseparable mixture of oxidized glutathione and a product that was identified as S-nitrosoglutathione. S-Nitrosoglutathione is known to be generated by reaction of nitrous acid with glutathione and furnishes a characteristic UV spectrum, but its NMR and mass spectral properties are described here for the first time. The 1H NMR spectrum of S-nitrosoglutathione showed in principle the resonance signals of glutathione except that the cysteine beta-protons gave two broad signals shifted downfield by 1 ppm as compared to the resonance frequencies of the glutathione cysteine beta-protons. The interpretation of the spectrum was aided by investigation of the properties of S-nitroso-N-acetylcysteine, the product of the reaction of N-acetylcysteine with propyl-2-nitronate. The nitronates of primary nitroalkanes, such as nitromethane, nitroethane, or 1-nitropropane, did not react with glutathione. The reaction between propyl-2-nitronate and glutathione did not occur at pH values greater than 5; therefore, the relevance of these findings to the disposition of propyl-2-nitronate in vivo is unclear.