Antioxidant potential of essential oil from Lavandula angustifolia in in vitro and ex vivo cultured liver cells.

Lavender is a commonly used herb in traditional medicine in Asia and Europe. It has been reported to be an effective medical plant in treating inflammation, depression and stress, thanks to its sedative and anxiolytic action, thrombotic, and antimicrobial properties. In the present study we investigated the protective effects of essential oil from Lavandula angustifolia (LO) against hydrogen peroxide and tert-butyl hydroperoxide -induced DNA damage. Also the effects of LO on the levels of enzymatic and non-enzymatic antioxidants (SOD-superoxide dismutase, GPx-glutathione peroxidase, GSH-glutathione) were evaluated in in vitro (human hepatoma cell line HepG2) and in ex vivo (freshly isolated rat hepatocytes) systems. The results showed that the oxidant-induced DNA lesions were significantly reduced in both systems pre-treated with the Lavandula angustifolia. The observed DNA-protective activity could be explained by both elevation of GPx activity in cells pre-treated with LO and antioxidant activity of LO.

Reduction of DNA-damaging effects of anti-HIV drug 3'-azido-3'-dideoxythymidine on human cells by ursolic acid and lignin biopolymer.

In this study we verified our assumption that the genotoxicity of the effective anti-HIV drug 3'-azido-3'-dideoxythymidine (AZT) on human cells could be reduced by non-toxic concentrations of two antioxidants that occur frequently in nature (ursolic acid and lignin biopolymer). Cytotoxicity of these natural compounds, well-known by their antimutagenic effects, was evaluated by the trypan blue exclusion technique. Genotoxic activity of AZT was measured on the basis of AZT-induced single and double strand breaks to DNA in two histopathologically different types of human cells, hepatoma cells HepG2 and colonic cells Caco-2. Induction of DNA strand breaks was measured by the comet assay processed in parallel at pH > or = 13.0 (standard alkaline technique which enables to recognize single strand DNA breaks of different origin) and at pH = 9.0 (neutral technique which enables to recognize double strand DNA breaks). As the level of AZT-induced double strand DNA breaks was rather low, protective effects of the antioxidants tested were evaluated only against AZT-induced single strand DNA breaks by the standard alkaline comet assay. Our findings showed that 1 h pre-incubation of cells with ursolic acid or lignin preceding to 3 h treatment of cells with AZT (3 mg/ml) significantly decreased in both cell types the level of AZT-induced single strand DNA breaks. Pre-incubation of HepG2 or Caco-2 cells with a mixture of both natural antioxidants did not increase the effects of individual treatments. This study confirms that AZT is genotoxic toward both used cell types of human origin and that ursolic acid and biopolymer lignin can protect the cells studied against genotoxic effect of AZT.

Electrochemical behavior and determination of tumor inhibiting or promoting activities of flavonoids.

This paper deals with determination of the tumor inhibiting or promoting activities of 11 flavonoids performed by DC polarography. Flavonoids were tested in the presence of polyaromatic carcinogen 7,12-dimethylbenz(a)anthracene (DMBA) or in combination with DMBA and 12-O-tetradecanoylphorbol-13-acetate (TPA), which is known as a specific tumor promoter for epidermal carcinogenesis. We found that in this experimental system the promotory or inhibitory activities of studied flavonoids depend on the number and position of hydroxyl groups in their chemical structures and are related to the polarographic behavior of these compounds. Flavonoids, which are hydroxylated at the ring B, are reduced in anhydrous DMF on a mercury dropping electrode in two one-electron steps. Absence of the hydroxyl groups in these positions caused their reduction in three one-electron steps. Similarly, flavonoids with hydroxyl groups at the ring B have been shown to inhibit the activities of DMBA (2.7-45.9%) and of DMBA + TPA (47.2-78.2%). Missing hydroxyl groups caused weaker inhibitory activity against DMBA + TPA (19.01-38.74%) and the enhancement of DMBA activity (31.08-66.21%). Presented data demonstrated that the electrochemical method--DC polarography is very sensitive, simple technique for determination of the tumor inhibiting or promoting activities of the studied compounds.