Comparative study of DNA-damaging and DNA-protective effects of selected components of essential plant oils in human leukemic cells K562.

Eucalyptol, carvacrol and thymol represent components of plant essential oils characterized by a wide range of biological effects toward microorganisms, fungi, insects, etc. However, till now only a few investigations have been carried out to study the effects of essential oils and their components on human cells cultured in vitro. The aim of our work was therefore to compare cytotoxic and DNA-damaging effects of eucalyptol, carvacrol and thymol on human leukemic K562 cells cultured in vitro and to investigate their possible protective (antioxidant) effects against hydrogen peroxide-induced DNA damage. Testing of cytotoxic activity was performed by the trypan blue exclusion technique. The amount of DNA lesions in K562 cells treated with the plant volatiles studied or their combinations with hydrogen peroxide (H2O2) was measured by alkaline single cell gel electrophoresis (SCGE; comet assay). We found out that eucalyptol, carvacrol and thymol differed in their cytotoxic and genotoxic effects on K562 cells. As a very important we consider the finding that carvacrol and thymol significantly reduced the level of DNA damage induced in K562 cells by the strong oxidant H2O2. Neither DNA-damaging nor DNA-protective effect was observed using eucalyptol pre-treatment of K562 cells. We assume that DNA-protective effects of carvacrol and thymol can be accompanied by their antioxidant action.