Chebulinic acid and tellimagrandin I inhibit DNA strand breaks by hydroquinone/Cu(II) and H2O2/Cu(II), but potentiate DNA strand breaks by H2O2/Fe(II)

The effects of two polyphenols, chebulinic acid and tellimagrandin I, on DNA strand breaks mediated by H2O2/Cu(II), hydroquinone (HQ)/Cu(II) and H2O2/Fe(II) in pBR322 plasmid DNA and genomic DNA of cultured MRC-5 human embryo lung fibroblasts were examined. The results demonstrated that chebulinic acid and tellimagrandin I obviously inhibited HQ/Cu(II)- and H2O2/Cu(II)-mediated pBR322 DNA strand breaks. When MRC-5 cells were treated with HQ/Cu(II), the presence of chebulinic acid or tellimagrandin I inhibited HQ/Cu(II)-mediated double strand breaks of genomic DNA. The presence of chebulinic acid or tellimagrandin I did not affect the H2O2- and HQ-mediated reduction of Cu(II) to Cu(I). Both polyphenols could slightly inhibit H2O2/Fe(II)-mediated plasmid DNA strand break at the lower concentration (1–10 μM), but potentiate the DNA strand break at the higher concentration (over 50 μM). These results demonstrated that chebulinic acid and tellimagrandin I possessed antioxidant action in certain conditions and exerted prooxidant action on DNA strand breaks in other conditions.