OBJECTIVES: To investigate cytotoxic, genotoxic and DNA-protective effects of carvacrol and thymol on human hepatoma HepG2 and colonic Caco-2 cells cultured in vitro. METHODS AND RESULTS: Cytotoxicity testing was performed by the trypan blue exclusion technique. Level of DNA lesions induced in human cells with carvacrol, thymol or their combinations with hydrogen peroxide (H(2)O(2)) were measured by alkaline single cell gel electrophoresis (comet assay). The trypan blue exclusion technique showed that though the metabolically more competent human hepatoma HepG2 cells were more sensitive to the toxic effects of carvacrol or thymol than colonic Caco-2 cells, which contained lower levels of metabolizing enzymes, the observed differences were not very expressive. The comet assay technique showed that at concentrations <IC(50) the compounds studied did not induce DNA strand breaks either in hepatoma HepG2 or in colonic Caco-2 cells. On the other side, 24-h incubation of cells in the presence of carvacrol or thymol led to a significant protection of the cells studied toward DNA damage induced by H(2)O(2). CONCLUSIONS: Based on our results it can be concluded that the cytotoxic effects of selected components of essential plant oils on human hepatoma HepG2 and colonic Caco-2 cells were not associated with a DNA-damaging effect. Carvacrol and thymol reduced the level of DNA lesions induced by H(2)O(2). We assume that the observed DNA-protective effects of these plant volatiles can be associated with their antioxidative activity.
OBJECTIVES: To investigate cytotoxic, genotoxic and DNA-protective effects of carvacrol and thymol on humanhepatoma HepG2 and colonic Caco-2 cells cultured in vitro. METHODS AND RESULTS:Cytotoxicity testing was performed by the trypan blue exclusion technique. Level of DNA lesions induced in human cells with carvacrol, thymol or their combinations with hydrogen peroxide (H(2)O(2)) were measured by alkaline single cell gel electrophoresis (comet assay). The trypan blue exclusion technique showed that though the metabolically more competent humanhepatoma HepG2 cells were more sensitive to the toxic effects of carvacrol or thymol than colonic Caco-2 cells, which contained lower levels of metabolizing enzymes, the observed differences were not very expressive. The comet assay technique showed that at concentrations <IC(50) the compounds studied did not induce DNA strand breaks either in hepatoma HepG2 or in colonic Caco-2 cells. On the other side, 24-h incubation of cells in the presence of carvacrol or thymol led to a significant protection of the cells studied toward DNA damage induced by H(2)O(2). CONCLUSIONS: Based on our results it can be concluded that the cytotoxic effects of selected components of essential plant oils on humanhepatoma HepG2 and colonic Caco-2 cells were not associated with a DNA-damaging effect. Carvacrol and thymol reduced the level of DNA lesions induced by H(2)O(2). We assume that the observed DNA-protective effects of these plant volatiles can be associated with their antioxidative activity.