Tobacco-specific and betel nut-specific N-nitroso compounds: occurrence in saliva and urine of betel quid chewers and formation in vitro by nitrosation of betel quid.

Abstract

In order to evaluate exposure of betel quid chewers to N-nitroso compounds, saliva and urine samples were collected from chewers of betel quid with or without tobacco, from tobacco chewers, from cigarette smokers and from people with no such habit, and were analysed for the presence of N-nitrosamines by gas chromatography coupled with Thermal Energy Analyzer and alkaloids derived from betel nut and tobacco by capillary gas chromatography fitted with nitrogen-phosphorous selective detector. The levels of the betel nut-specific nitrosamines, N-nitrosoguvacoline and N-nitrososoguvacine (the latter being detected for the first time in saliva), ranged from 0 to 7.1 and 0 to 30.4 ng/ml, respectively. High levels of tobacco-specific nitrosamines were detected in the saliva of chewers of betel quid with tobacco and in that of chewers of tobacco, ranging from 1.6 to 59.7 (N'-nitrosonornicotine), 1.0 to 51.7 (N'-nitrosoanatabine) and 0 to 2.3 [4-(methyl-nitrosamino)-1-(3-pyridyl)-1-butanone] ng/ml. Urinary concentrations of certain N-nitrosamino acids, including N-nitrosoproline, were determined as a possible index of exposure to nitroso compounds and their precursors in the study groups: no clear difference was observed. The betel nut-specific alkaloid, arecoline, was present at high levels in the saliva of betel quid chewers with or without tobacco. Nicotine and cotinine were also detected in saliva and urine of chewers of tobacco and of betel quid with tobacco. In order to assess whether N-nitroso compounds are formed in vivo in the oral cavity during chewing or in the stomach after swallowing the quids, the levels of N-nitroso compounds in betel quid extracts were determined before and after nitrosation at pH 7.4 and 2.1. The results indicate that N-nitroso compounds could easily be formed in vivo. The possible role of N-nitroso compounds in the causation of cancer of the upper alimentary tract in betel quid chewers is discussed.