In vitro DNA-damaging effects of intestinal and related tetrapyrroles in human cancer cells

► DNA-damaging effects of bile pigments have been rarely investigated. ► Thus, eight tetrapyrroles were tested for DNA-damaging effects in the comet assay. ► To assess DNA damage, cancer cells were used, and flow cytometry parameters were measured. ► Especially protoporphyrin, urobilin and stercobilin increased DNA strand breaks significantly. ► Mechanisms could include oxidative stress, cell cycle arrest and apoptosis.