J. Nair

Formation of reactive oxygen species and of 8-hydroxydeoxyguanosine in DNA in vitro with betel quid ingredients

The formation of reactive oxygen species (ROS) from betel quid ingredients, namely areca nut, catechu and tobacco, was studied using a chemiluminescence (CL) technique. Aqueous extracts of areca nut and catechu were capable of generating superoxide anion and hydrogen peroxide at pH greater than 9.5. The formation of O2 was enhanced by Fe2+, Fe3+ and Cu2+ but inhibited by Mn2+. Tobacco extract failed to generate ROS under similar conditions. Saliva was found to inhibit both O2 and H2O2 formation from betel quid ingredients. Upon incubation of DNA at alkaline pH with areca nut extract and Fe3+ or catechu, 8-hydroxydeoxyguanosine was formed as quantified by high performance liquid chromatography (HPLC)/electrochemical detection. The data suggest a possible role of reactive oxygen species in the etiology of oral cancer in betel quid chewers.

Identification, occurrence and mutagenicity in Salmonella typhimurium of two synthetic nitroarenes, musk ambrette and musk xylene, in Indian chewing tobacco and betel quid

During N-nitrosamine analysis of extracts of betel quid with tobacco and of the saliva of chewers of betel quid with tobacco for N-nitrosamines using a Thermal Energy Analyzer, two unknown compounds were detected. They were identified as synthetic nitro musks, musk ambrette (5-tert-butyl-1,3-dinitro-4-methoxy-2-methylbenzene, CAS No. 83-66-9) and musk xylene, (1-tert-butyl-3,5-dimethyl-2,4,6-trinitrobenzene, CAS No. 81-15-2), by gas chromatography-mass spectrometry and Fourier transform nuclear magnetic resonance spectroscopy. These compounds were detected in several samples of betel quid with tobacco and in perfumed tobacco used for chewing in India in amounts ranging from 0.45-23.5 mg/g wet weight. Musk ambrette was found to be mutagenic in Salmonella typhimurium TA100 requiring metabolic activation by rat-liver postmitochondrial supernatant but musk xylene lacked mutagenicity.

N-nitrosamines in the saliva of tobacco chewers or masheri users

Saliva was collected from men and women who were habitual chewers of tobacco (with lime or betel quid) and from women who used masheri. The saliva was analysed for tobacco-specific nitrosamines (TSNAs). TSNAs were detected in the saliva of all tobacco users, but within each habit group there were wide variations between donors in salivary nitrosamine levels. TSNA levels in the saliva from men and women chewing betel quid and tobacco were similar, although women used less tobacco for chewing. The saliva of men who chewed tobacco with lime contained higher levels of TSNAs than did that of men who chewed betel quid with tobacco.

Identification and occurrence of two new N-nitrosamino acids in tobacco products: 3-(N-nitroso-N-methylamino) propionic acid and 4-(N-nitroso-N-methylamino) butyric acid

Two new N-nitrosamino acids, 3-(N-nitroso-N-methylamino)propionic acid (CAS: 10478-42-9) and 4-(N-nitroso-N-methylamino)butyric acid (CAS: 61445-55-4) were isolated and identified for the first time in various types of tobacco, including snuff, chewing and pipe tobacco, cigars and cigarettes. Their levels ranged from 0.15 to 7.4 and 0 to 2.2 mg/kg of dry weight tobacco, respectively. For comparison, amounts of other N-nitrosamino acids like N-nitrosoproline (NPRO) and tobacco-specific-nitrosamines (TSNA) were determined in the same samples. The levels of N-nitrosamino acids were highly correlated with the levels of TSNA.

Modifiers of Endogenous Nitrosamine Synthesis and Metabolism

N-Nitroso compounds (NOCs), a class of versatile carcinogens (1,13), are formed in nature, most likely since mankind first existed on earth, whenever nitrosating agents such as nitrite or nitrosating gases encounter nitrosatable amines. To date, more than 300 NOCs have been tested in animals, and about 90% of them produced tumors in 40 animal species, including primates. Humans are exposed to NOCs from exogenous and endogenous sources through nitrosation of ingested/inhaled amino precursors. Nitrite is produced by bacterial reduction of nitrate, normally in the mouth, and the nitrosation reaction generally proceeds through an acid-catalyzed reaction in the stomach. Any nitrosation reaction occurring in vivo is, however, affected by many factors, such as the pH, precursor concentration, and the presence of catalysts and inhibitors. These various factors, some of which are difficult to measure in vivo, have complicated the estimation of nitrosation reactions occurring in humans.