Precursors of N-nitroso compounds in some Nigerian medicinal plants

Twenty-seven tropical plants of medicinal importance were analysed for primary and secondary amines by chemiluminescence detection on a Thermal Energy Analyzer (TEA) modified for use on 'nitrogen mode' following derivatization with benzene sulphonyl chloride (BSC) and gas chromatographic (GC) separation of their sulphonamides. Nitrite was determined by colorimetry at 540 nm after diazotization with sulphanilamide and coupling with N-(1-naphthyl)ethylenediamine to form an azo dye. Nitrate was determined as nitrite following on-line reduction by granulated cadmium. Dimethylamine in the range of 0.5 ppm to 18.2 ppm was detected in 96% of samples, while pyrrolidine ranged between 0.7 ppm and 12.78 ppm in 14 samples. Isobutylamine, methylamine and ethylamine were the most ubiquitous primary amines. Largest number of secondary amines (four) was found in Azadirachta indica (Neem) while largest number of primary amines (six) was detected in Azadirachta indica and Tamarindus indica (Tsamiya) which also contained the highest amount of total primary amines (148.8 ppm). Nitrate and nitrite were seldom found in plant extracts whose pH were generally below 7.0. These findings suggests that early exposures to precursors of N-nitroso compounds via medicinal plants might contribute to total risk posed by environmental carcinogens in Nigeria.