The aim of this study was to investigate the protective effect of
myricetin,
quercetin, (+)-
catechin and (-)-
epicatechin, against
N-nitrosodibutylamine (NDBA) and
N-nitrosopiperidine (
NPIP)-induced DNA damage in human
hepatoma cells (HepG2). DNA damage (strand breaks and oxidized
purines/
pyrimidines) was evaluated by the alkaline single-cell gel electrophoresis or Comet assay. (+)-
Catechin at the lowest concentration (10 microM) showed the maximum reduction of
DNA strand breaks (23%), the formation of
endonuclease III (Endo III, 19-21%) and
formamidopyrimidine-DNA glycosylase (Fpg, 28-40%) sensitive sites induced by NDBA or
NPIP. (-)-
Epicatechin also decreased
DNA strand breaks (10 microM, 20%) and the oxidized
pyrimidines/
purines (33-39%) induced by NDBA or
NPIP, respectively.
DNA strand breaks induced by NDBA or
NPIP were weakly reduced by
myricetin at the lowest concentration (0.1 microM, 10-19%, respectively).
Myricetin also reduced the oxidized
purines (0.1 microM, 17%) and
pyrimidines (0.1 microM, 15%) induced by NDBA, but not the oxidized
pyrimidines induced by
NPIP.
Quercetin did not protect against NDBA-induced DNA damage, but it reduced the formation of Endo III and Fpg sensitive sites induced by
NPIP (0.1 microM, 17-20%, respectively). In conclusion, our results indicate that (+)-
catechin and (-)-
epicatechin at the concentrations tested protect human derived cells against oxidative DNA damage effects of NDBA and
NPIP. However,
myricetin at the concentrations tested only protects human cells against oxidative DNA damage induced by NDBA and
quercetin against oxidative DNA damage induced by
NPIP.