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Caffeine and Other Methylxanthines as Interceptors of Food-Borne Aromatic Mutagens: Inhibition of Trp-Pâ1 and Trp-Pâ2 Mutagenic Activity
Caffeine is one of the most important
biologically active food
components. In this article, we demonstrate that caffeine and other
methylxanthines significantly reduce the mutagenic activity of two
food-derived heterocyclic aromatic amines, Trp-P-1 and Trp-P-2 in
the <i>Salmonella typhimurium</i> TA98 strain. Moreover,
protection against Trp-P-1-induced mutagenicity was independent of
liver S9 enzymatic fraction, suggesting that mechanisms other than
modulation of mutagen bioactivation can contribute to the observed
protective effects. UVâvis spectroscopy and computational studies
revealed that methylxanthines intercept Trp-P-1 and Trp-P-2 in noncovalent
molecular complexes, with association constants (<i>K</i><sub>AC</sub>) in the 10<sup>2</sup> M<sup>â1</sup> range.
Enthalpy values (Î<i>H</i> about â30 kJ·mol<sup>â1</sup>) of mutagenâmethylxanthine heterocomplexation
obtained microcalorimetrically correspond to stacking (ÏâÏ)
interactions. Finally, we demonstrated that the biological activity
of Trp-P-1 and Trp-P-2 is strictly dependent on the presence of the
mutagen in a free (unbound with methylxanthine) form, suggesting that
mutagen sequestration in stacking heterocomplexes with methylxanthines
can decrease its bioavailability and diminish its biological effects