Experimental, Spectroscopic, and Computational Insights into the Reactivity of "Methanal" with 2-Naphthylamines

The reactions of 2-naphthylamine and methyl 6-amino-2-naphthoate with formalin and paraformaldehyde were studied experimentally, spectrally, and by quantum chemical calculations. It was found that neither the corresponding aminals nor imines were formed under the described conditions but could be prepared and spectrally characterized at least in situ under modified conditions. Several of the previously undescribed intermediates and by-products were isolated or at least spectrally characterized. First principle density functional theory (DFT) calculations were performed to shed light on the key aspects of the thermochemistry of decomposition and further condensation of the corresponding aminals and imines. The calculations also revealed that the electrophilicity of methanal was significantly greater than that of ordinary oxo-compounds, except for perfluorinated ones. In summary, methanal was not behaving as the simplest aldehyde but as a very electron-deficient oxo-compound.

[A new method for the determination of naphatylamines in workplace air for occupational exposure assessment]

BACKGROUND

Naphthylamine (NA), i.e., 1-naphthylamine (1-NA) and 2-naphthylamine (2-NA) and its salts (2-naphthylamine hydrochloride and 2-naphthylamine acetate) are colorless crystalline solids. They have been used, among others, in the production of paints and dyes. In the European Union, 1-NA is classified as a toxic substance, and 2-NA and its salts as carcinogenic category 1A. The aim of this study was to develop a new method for the determination of NA, which will enable the determination of 1-NA and 2-NA and its salts in the working environment, in the concentration range of 0.3-6 μg/m³.

MATERIAL AND METHODS

The method consists in passing the test air containing the substances to be determined through a glass fiber filter impregnated with sulphuric acid(VI). After recovery with water and sodium hydroxide solution followed by extraction into a solid on Oasis HLB columns, the solutions in methanol are analyzed using a high-performance liquid chromatograph with a fluorescence detector and Ultra C18 column.

RESULTS

The method developed allows determining 1-NA and 2-NA and its salts in the concentration range of 0.3-6 μg/m³. The limit of detection for 1-NA is 81 pg/ml and for 2-NA - 80.6 pg/ml.

CONCLUSIONS

The method is characterized by good precision and accuracy; it meets the requirements of European Standard PN-EN 482 and can be used by occupational hygiene laboratories to measure the level of 1-NA and 2-NA and its salts in workplace air to assess workers' exposure to these substances. Med Pr. 2021;72(2):145-54.

Oxidative DNA damage induced by a metabolite of 2-naphthylamine, a smoking-related bladder carcinogen

2-Naphthylamine (2-NA), a bladder carcinogen, is contained in cigarette smoke. DNA adduct formation is thought to be a major cause of DNA damage by carcinogenic aromatic amines. We have investigated whether a metabolite of 2-NA, 2-nitroso-1-naphthol (NO-naphthol) causes oxidative DNA damage, using (32)P-labeled DNA fragments. We compared the mechanism of DNA damage induced by NO-naphthol with that by N-hydroxy-4-aminobiphenyl (4-ABP(NHOH)), a metabolite of 4-aminobiphenyl, another smoking-related bladder carcinogen. NO-naphthol caused Cu(II)-mediated DNA damage at T > C > G residues, with non-enzymatic reduction by NADH. Catalase and bathocuproine, a Cu(I)-specific chelator, inhibited the DNA damage, suggesting the involvement of H(2)O(2) and Cu(I). Some free. OH scavengers also attenuated NO-naphthol-induced DNA damage, while free. OH scavengers had no effect on the DNA damage induced by 4-ABP(NHOH). This difference suggests that the reactive species formed by NO-naphthol has more free. OH-character than that by 4-ABP(NHOH). A high-pressure liquid chromatograph equipped with an electrochemical detector showed that NO-naphthol induced 8-oxo-7,8-dihydro-2'-deoxyguanosine formation in the presence of NADH and Cu(II). The oxidative DNA damage by these amino-aromatic compounds may participate in smoking-related bladder cancer, in addition to DNA adduct formation.