- 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.