Protective Effects of Aqueous and Ethanolic Extracts of Portulaca oleracea L. Aerial Parts on H2O2- Induced DNA Damage in Lymphocytes by Comet Assay

The comet assay is a standard method for measuring DNA damage. In this study, the protective effects of ethanolic and aqueous extracts of Portulaca oleracea L. (P. oleracea) on human lymphocyte DNA lesions were evaluated with the comet assay. Lymphocytes were isolated from blood samples taken from healthy volunteers. Human lymphocytes were incubated in H2O2 (50,100, and 200 mu M), aqueous extract (0.05, 0.1, 0.5, 1, and 2.5 mg/ml), and ethanolic extracts (0.05, 0.1, 0.5, 1, and 2.5 mg/ml) of P. oleraceae aerial parts alone with a combination of H2O2 (100 mM) with either 1 or 2.5 mg/ml of both extracts at 4 degrees C for 30 minutes. The extent of DNA migration was measured using the alkaline single cell gel electrophoresis approach assay, and DNA damage was expressed as percentage tail DNA. We found that the aqueous extract of P. oleracea significantly inhibited DNA damage, while there was no effect of the ethanolic extract. These data suggest that the aqueous extract of P. oleracea can prevent oxidative DNA damage to human lymphocytes, which is likely due to antioxidant constituents in the extract.