PRESENCE OF N-NITROSAMINES AND RELATED COMPOUNDS IN HUMAN AND ANIMAL FOODS

Abstract

The nitrosamine, nitrate, ntirite and amine contents of some indigenous vegetables, soup condiments, cereals, food staples and forages of tropical interest were investigated. Also examined were the nitrosation of these foods- and feedstuffs, in vitro, under simulated gastric conditions; the interaction of nitrosodiphenylamine with bile constituents and pharmacokinetic differences in biliary excretion of the nitrosamine in mammals due to their species and sexes. Methods employed include; gas chromatography – with – chemiluminescence detection for nitrosamines and amines, spectrophotometry for nitrite and nitrate following cadmium reduction of nitrate and diazotization of nitrite with sulphanilamide, and coupling with N(1-naphthyl) ethylenediamine, and for unchanged N-nitrosodiphenylamine alter cannulation of the bile duct of dosed animals and irradiating bile with short wave U.V. light: and for bile constituents using an autoanalyzer and flame photometry. High levels of nitrate were found in many foodstuffs, especially vegetables (max. 2948 ppm). Dimethylamine, pyrrolidine, methylamine and ethylamine were the most common amines found. Total primary amine was highest in Talinum triagulare (566 ppm), while total identifiable secondary amines was high in Amaranthus hybridus (180 ppm). Nitrosation under simulated gastric conditions resulted in the formation of only N-nitrosodiphenylamine (NDMA), except in Tellairia occidentalis where N-nitrosopiperidine (NPIP) was also detected. Preformed nitrosamine was detected in 75% of the samples analysed, as NDMA, in levels ranging between 0.4 and 4.6 ppb, the highest value being found in Brassica Oleraceae. Studies on animal forages show between 0.6 ppb and 4.4 ppb of NDMA in 83% of samples, and NPIP (1.6 ppb) in one of the (Dichrostachys cinerea). Dimethlamine pyrrolidine, ethylamine, methylamine and isopentylamine were the most ubiquituos amines in these materials. Urena lobeta contained the highest amount of total primary amines (95 ppm) and secondary amines (93 ppm). Nitrosation of the forages under quasi-gastric conditions yielded only low levels of NDMA (0 -1.4 ppb). But nitrosation under chemical conditions produced high concentrations of volatile nitrosamines (up to 1118 ppb). Two hours after administering N-nitrosodiphenylamine (NDPHA) to the rat concentration of Na+, Cr and Ca2+ decreased while levels of k+, PO₄ HCO₃, Urea and creatinine increased. Total protein content was normal. The guinea pig transported the compound into the bile fastest, while the rabbit, which transported it slowest, eliminated the nitosamine fastest. Both appearance and disappearance of the nitrosamine was slowest in the rat. N-nitrosodiphenylamine elimination half life values were 510, 240 and 95 min in rat, guinea pig rabbit respectively. The cumulative excretions amounted to 12.3 and 0.3%. Biliary excretion of the compound in the sexes displayed biphasic kinetics.