Ochratoxin A reduces aflatoxin B1 induced DNA damage detected by the comet assay in Hep G2 cells

► Genotoxicity of combined treatments of ochratoxin A (OTA) and aflatoxin B1 (AFB1) in Hep G2 cells. ► DNA damage evaluated by the comet assay using restriction enzymes FPG and endo III. ► 3 h + S9 mix and 24 h treatments of AFB1 increased DNA strand breaks and AP sites; FPG detected additional strand breaks. ► OTA gave negative results but produced a significant decrease of AFB1 genotoxicity. ► A possible explanation may be that AFB1 and OTA compete for the same CYP enzymes representing a bioactivation route for AFB1.