In vitro protective effects of Scutellaria litwinowii root extract against H 2 O 2 -induced DNA damage and cytotoxicity

BACKGROUND: Despite the wide range of investigations on the therapeutic potentials of herbal extracts in cancer cell lines, there is not usually enough data on their probable effects on normal cells. Recently, both anti-tumoral and anti-oxidant properties of Scutellaria litwinowii extracts have been reported on different cancer cell lines. In the present study, the possible protective effects of S. litwinowii root extracts against cytotoxicity and DNA damage induced by hydrogen peroxide (H2O2) on normal cells were investigated using MTT and Comet assays, respectively. METHODS: A method of sequential extraction with solvents of different polarities was used to generate methanolic, de-fatted, and dichloromethane fractions. Both MTT and Comet assays were performed here to assess, respectively, changes in cell viability and levels of DNA damage from H2O2. In a pre-treatment regimen, test materials were applied to the cells prior to H2O2 treatment, while in a co-treatment protocol, cells were treated simultaneously with H2O2 and extracts. RESULTS: In the co-treatment studies, only methanolic extract at 1,000 μg/mL (p<0.001) imparted a significant protective effect as shown in the MTT assay. Pre-treatment of cells for 24 h with different concentrations of the test materials did not lead to any significant protection. Results from the Comet assays in the co-treatment studies suggested a significant (p<0.01) protective effect of the test materials against DNA damage caused by H2O2. However, in the pre-treatment studies, only methanolic extract at ≥500 μg/mL showed a protective effect (p<0.01). CONCLUSIONS: Considering the probable high levels of phenolic and flavonoid compounds in the methanolic extract, these compounds may impart the noted protective effects of the S. litwinowii root through the scavenging of free radicals.