Measurement of the influence of flavonoids on DNA repair kinetics using the comet assay

The complexity of DNA repair mechanisms infers that xenobiotics, derived from food and medicinal plants, may interfere in the process, activating or inhibiting repair. Different flavonoids were investigated, at the highest non-toxic concentration, for their capacity to modulate DNA repair 12, 24 and 48 h after a non-reactive oxygen species (ROS) treatment involving ethylmethanesulfonate (2 mM; 2 h). After 12 h, DNA fragmentation is substantially increased by quercetin; this effect disappears at subsequent sampling times. At 24 h, fragmentation is reduced in the presence of apigenin and slightly increased by sakuranetin. None of the flavonoids tested inhibited repair, which seems complete at 48 h. Ex vivo comet experiments were then performed to assess the excision capabilities of protein extracts obtained from flavonoid-treated cells. Quercetin increases non-specific endonuclease activity, apigenin and epicatechin increase the excision of damages and sakuranetin increases both non-specific and specific enzymatic activities. Combining direct repair and ex vivo experiments yields complementary data that may lead to characterizing mechanisms.