Graduate Thesis Or Dissertation
 

Formation of N-nitrosamines from the nitrosation of spermidine and spermine

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  • The reactions between sodium nitrite and the polyamines spermidine and spermine were investigated. When reacted at 80°C for 1 hr at pH 3.5 with a 1:3 molar ratio of amine groups to sodium nitrite, five volatile nitrosamines were identified as products in the nitrosation of spermidine. 3HC1, and two volatile nitrosamines were identified from spermine 4HC1. The principal volatile nitrosation product both from spermidine and spermine was γ-butenyl(β-propenyl)nitrosamine (BPN). The identification of this compound was based on the spectral characteristics of the compound using mass, infrared, and nuclear magnetic resonance spectrometry. To confirm the identity, BPN was synthesized from γ-butenyl(β-propenyl)amine and sodium nitrite, and the spectra obtained for this substance and the unknown compound were compared. The amine precursor was synthesized from allylamine and l-Bromo-4-butene. Two hydroxylated, dialkyl nitrosamines were identified as products from spermidine 3HC1: γ-butenyl(γ-propanol)nitrosamine and δ-butanol(β-propenyl)nitrosamine. The compounds were characterized by mass and infrared spectrometry, and by the Griess test for nitrosamines. The structures were confirmed by making the trifluoroacetate derivatives of the compounds, and obtaining their mass spectra. In the presence of chloride ions, chlorinated dialkyl nitrosamines were tentatively identified as nitrosation products from spermidine. The identification was based on mass spectrometry, particularly the isotope effects by chlorine, and by the Griess test. It appeared that δ-butylchloride(β-propenyl)nitrosamine probably was a major isomer, but other structural isomers may also be formed. The nitrosamines described above have previously not been synthesized or characterized. Their individual carcinogenic potency therefore is not known. Nitrosopyrrolidine, which was a nitrosation product both from spermidine and spermine, is a potent carcinogen. The yields of the individual nitrosamines from spermidine 3HC1 and spermine 4HC1 were, respectively: BPN, 1.7%, 1. 4%; γ-butenyl(γ- propanol)nitrosamine, 0, 29%, 0%; δ-butanol(β-propenyl)nitrosamine, 0.18%, 0%; δ-butylchloride(β-propenyl)nitrosamine (and its isomers), 0, l2%, 0%; nitrosopyrrolidine3 0.60% and trace amounts. The yields were estimated on the basis of the amount of polyamine precursor. Maximum accumulation of all nitrosamines from spermidine was observed between pH 3.0 and 4.5, when reacting for 1 hr at 50°C, Increasing the reaction time to 25 hrs at 50°C, the yield of BPN at pH 5.0 exceeded the yield at pH 3.5. From the temperature effect on the nitrosation rate, activation energy for the formation of BPN from spermidine and nitrite was estimated to be 19 kcal/mol. In the presence of 0.1-1 M sodium chloride at pH 4.0, no significant effects on the yields of BPN, γ-butenyl(γ-propanol)nitrosamine and δ-butanol (β-propenyl)nitrosamine were observed, while the yield of δ-butylchloride (β-propenyl)nitrosamine (and its isomers) was strongly enhanced with increased sodium chloride concentration. The yields of all nitrosamines were drastically reduced in the presence of 1.5 M or 2.0 M sodium chloride in the system. In the nitrosation of proline, sodium chloride in concentrations up to 1 M strongly activated the reaction at pH 0.5. Small inhibiting effects were observed at pH 2.5, however, and moderate inhibition by sodium chloride was seen at pH's 4.0 and 5.5. Multiple regression analysis showed the best fitted model was of the form, log (initial rate of nitrosation) = a + b[ NaCl] + c[ NaCl]² at all pH levels tested.
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