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.