Modulation of the mutagenicity of food carcinogens by oligomeric and polymeric procyanidins isolated from grape seeds: synergistic genotoxicity with N-nitrosopyrrolidine
F. Catterall et al., Modulation of the mutagenicity of food carcinogens by oligomeric and polymeric procyanidins isolated from grape seeds: synergistic genotoxicity with N-nitrosopyrrolidine, J SCI FOOD, 80(1), 2000, pp. 91-101
Oligomeric and polymeric procyanidins were isolated from grape seeds, and t
heir antimutagenic potential against food carcinogens was evaluated in the
Ames test. Both procyanidins suppressed the mutagenicity of IQ and benzo[a]
pyrene but did not modulate the mutagenic activity of MNNG. At the concentr
ations where antimutagenic activity was expressed, the oligomeric and polym
eric procyanidins inhibited the hepatic O-dealkylation of methoxy- and etho
xyresorufin. It is concluded that the antimutagenic activity exhibited by o
ligomeric and polymeric procyanidins is the consequence of inhibition of CY
P1A-mediated bioactivation. In contrast with these findings, oligomeric and
polymeric procyanidins potentiated the mutagenicity of N-nitrosopyrrolidin
e; the monomeric tea flavanols (+)-catechin and (-)-epicatechin also elicit
ed the same effect. Both the flavanols and procyanidins, at the concentrati
ons studied, failed to elicit a mutagenic response in the Ames test, either
in the presence or absence of an activation system. Incorporation of catal
ase and superoxide dismutase to the activation system failed to prevent the
synergistic effect between (+)catechin and the nitrosamine. The mutagenic
activity of N-nitrosopyrrolidine was much higher when the bacteria were gro
wn in nutrient broth supplemented with (+)-catechin compared with bacteria
grown in nutrient broth alone. It may be cautiously inferred that the syner
gistic genotoxicity between polyphenolics and N-nitrosopyrrolidine involves
interaction of (+)-catechin with bacterial DNA, facilitating the covalent
binding of the ultimate carcinogens of the nitrosamine to the DNA. (C) 2000
Society of Chemical Industry.