Protective action of plant polyphenols on radiation-induced chromatid breaks in cultured human cells.

The present study was performed to determine whether plant polyphenols can protect human cells against radiation-induced DNA damage manifested as chromatid breaks. Since each chromatid contains a single continuous molecule of double stranded DNA, chromatid breaks represent unrepaired DNA strand breaks. The addition of green or black tea extracts, their polyphenols or curcumin to cultures of human skin fibroblasts or PHA-stimulated blood lymphocytes significantly reduced the frequencies of radiation-induced chromatid breaks. An exception to this general finding was that the green tea polyphenol, (-)epigallocatechin gallate, had no effect. The protective action of these plant polyphenols seems to result from their known antioxidant properties, particularly the scavaging of hydroxyl free radicals. Frequencies of chromatid breaks in cells arrested immediately after irradiation or 0.5 to 1.5 hours post-irradiation in the presence or absence of a DNA repair inhibitor, provide a measure of DNA damage. The results of the present study show that tea and other plant polyphenols can protect human cells against radiation-induced DNA damage.