The protective ability of the Mediterranean plant extracts against the oxidative DNA damage. The role of the radical oxygen species and the polyphenol content.

The polyphenol plant extracts content seems to be responsible for the scavenging activity of the reactive oxygen species (ROS), resulting in protection against DNA damage induced by the oxidative stress. This assumption was verified analyzing the effect of six Mediterranean plant extracts (Crepis vesicaria L, Origanum heracleoticum, Scandix australis L, Amaranthus sp., Scolymus hispanicus L, Thymus piperella L) on the oxidative DNA damage induced in lymphocytes by H 2O 2 in relation to the polyphenolic content and the lymphocyte scavenging ability of ROS. The comet assay was used to evaluate oxidative DNA damage and the polyphenol content was analyzed by the Folin-Ciocalteu method. The fluorescence resulting from oxidation of ROS-sensitive dye, dihydrorofluorescein (DHF), was utilized as indicator of the ROS level. Pretreatment with all plant extracts produced the dose-dependent increase in the DNA protection up to the 0.2 μg/ml polyphenol content and the decrease above that dose. Only the Thymus piperella, similarly to quercetin, showed a strong positive correlation between the DNA protection and the polyphenol content, but negative correlation with ROS formation. In conclusion, the DNA protective ability of plant extracts seems to be related to the low polyphenol concentration and only to certain extent depends on the polyphenol ROS scavenging activity.