Hyperforin Exhibits Antigenotoxic Activity on Human and Bacterial Cells.

Hyperforin (HF), a substance that accumulates in the leaves and flowers of Hypericum perforatum L. (St. John's wort), consists of a phloroglucinol skeleton with lipophilic isoprene chains. HF exhibits several medicinal properties and is mainly used as an antidepressant. So far, the antigenotoxicity of HF has not been investigated at the level of primary genetic damage, gene mutations, and chromosome aberrations, simultaneously. The present work is designed to investigate the potential antigenotoxic effects of HF using three different experimental test systems. The antigenotoxic effect of HF leading to the decrease of primary/transient promutagenic genetic changes was detected by the alkaline comet assay on human lymphocytes. The HF antimutagenic effect leading to the reduction of gene mutations was assessed using the Ames test on the standard Salmonella typhimurium (TA97, TA98, and TA100) bacterial strains, and the anticlastogenic effect of HF leading to the reduction of chromosome aberrations was evaluated by the in vitro mammalian chromosome aberration test on the human tumor cell line HepG2 and the non-carcinogenic cell line VH10. Our findings provided evidence that HF showed antigenotoxic effects towards oxidative mutagen zeocin in the comet assay and diagnostic mutagen (4-nitroquinoline-1-oxide) in the Ames test. Moreover, HF exhibited an anticlastogenic effect towards benzo(a)pyrene and cisplatin in the chromosome aberration test.

Photoactivated hypericin is not genotoxic.

The study was designed to test the potential photogenotoxicity of hypericin (HYP) at three different levels: primary DNA damages, gene mutations and chromosome aberrations. Primary genetic changes were detected using the comet assay. The potential mutagenic activity of HYP was assessed using the Ames/Salmonella typhimurium assay. Finally, the ability of photoactivated HYP to induce chromosome aberrations was evaluated by the in vitro mammalian chromosome aberration test and compared to that of non-photoactivated HYP. The results have shown that photoactivated HYP can only induce primary DNA damages (single-strand DNA breaks), acting in a dose-response manner. This activity depended both on HYP concentrations and an intensity of the light energy needed for its photoactivation. However, mutagenic effect of photoactivated HYP evaluated in the Ames assay using three bacterial strains S. typhimurium (TA97, TA98 and TA100) was not confirmed. Moreover, photoactivated HYP in the range of concentrations (0.005-0.01 µg/ml) was not found to be clastogenic against HepG2 cells. Our findings from both the Ames assay and the chromosome aberrations test provide evidence that photoactivated HYP is not genotoxic, which might be of great importance mainly in terms of its use in the photodynamic therapy.

Extract from Armoracia rusticana and its flavonoid components protect human lymphocytes against oxidative damage induced by hydrogen peroxide.

DNA damage prevention is an important mechanism involved in cancer prevention by dietary compounds. Armoracia rusticana is cultivated mainly for its roots that are used in the human diet as a pungent spice. The roots represent rich sources of biologically active phytocompounds, which are beneficial for humans. In this study we investigated the modulation of H2O2 genotoxicity using the A. rusticana root aqueous extract (AE) and two flavonoids (kaempferol or quercetin). Human lymphocytes pre-treated with AE, kaempferol and quercetin were challenged with H2O2 and the DNA damage was assessed by the comet assay. At first we assessed a non-genotoxic concentration of AE and flavonoids, respectively. In lymphocytes challenged with H2O2 we proved that the 0.0025 mg·mL⁻¹ concentration of AE protected human DNA. It significantly reduced H2O2-induced oxidative damage (from 78% to 35.75%). Similarly, a non-genotoxic concentration of kaempferol (5 µg·mL⁻¹) significantly diminished oxidative DNA damage (from 83.3% to 19.4%), and the same concentration of quercetin also reduced the genotoxic effect of H2O2 (from 83.3% to 16.2%). We conclude that AE, kaempferol and quercetin probably act as antimutagens. The molecular mechanisms underlying their antimutagenic activity might be explained by their antioxidant properties.

Dual activities of emodin--DNA protectivity vs mutagenicity.

OBJECTIVES: Emodin is a bioactive anthraquinone that has diverse biological effects. It is also known as a biosynthetic precursor of hypericin. The purpose of this study was to assess mechanisms of potential genotoxic and antioxidant effects of emodin. We also investigated the potential genotoxic effect of photoactivated emodin. METHODS: Potential genotoxicity was determined by the alkaline comet assay and the Ames test. The potential DNA protectivity of emodin was determined by the DNA-topology assay. On purpose to clarify molecular mechanism of its DNA protectivity against Fe(2+)-induced DNA breaks, three different assays were used (Reducing power-, DPPH- and Fe(2+)-chelating assay). RESULTS: Using the alkaline comet assay and the Ames test we confirmed the genotoxic effect of both non-photoactivated and photoactivated emodin in a dose-dependent manner. Genotoxicity of photoactivated emodin did not differ from that obtained with non-photoactivated one. The DNA-topology assay revealed a DNA-protective activity of emodin. In the reducing power and DPPH assays emodin exhibited weak antioxidant activities. We did not observe any chelating activity of emodin in the Fe(2+)-chelating assay. CONCLUSIONS: We found out that emodin exhibited dual activities. On one side it was genotoxic inducing primary DNA lessions (determined by the comet assay) as well as gene mutations (determined by the Ames test). On the other side it exhibited DNA-protective activity (determined by the DNA-topology assay). Molecular mechanism underlying this DNA protective effect can be attributed to its free radicals scavenging and reducing activities.