Chebulinic acid and tellimagrandin I inhibit DNA strand breaks by hydroquinone/Cu(II) and H(2)O(2)/Cu(II), but potentiate DNA strand breaks by H(2)O(2)/Fe(II).

The effects of two polyphenols, chebulinic acid and tellimagrandin I, on DNA strand breaks mediated by H(2)O(2)/Cu(II), hydroquinone (HQ)/Cu(II) and H(2)O(2)/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 H(2)O(2)/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 H(2)O(2)- and HQ-mediated reduction of Cu(II) to Cu(I). Both polyphenols could slightly inhibit H(2)O(2)/Fe(II)-mediated plasmid DNA strand break at the lower concentration (1-10 microM), but potentiate the DNA strand break at the higher concentration (over 50 microM). 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.