TOXIC EFFECTS OF SOME CONIFER RESIN ACIDS AND TEA TREE OIL ON HUMAN EPITHELIAL AND FIBROBLAST CELLS

The present study was undertaken to assess and compare the in vitro cy totoxic effects of three resin acid analogues: dehydroabietic acid, po docarpic acid, O-methylpodocarpic acid; an essential oil from Australi a (tea tree oil); and tapped oleoresin from Thailand, on human epithel ial and fibroblast cells, using a quantitative neutral red spectrophot ometric assay. All of the investigated compounds except for tea tree o il exhibited a cytotoxic activity which was proportional to their conc entrations and time of exposure up to 24 h, i.e. higher concentrations and longer time of exposure caused increased cell death. Dehydroabiet ic acid and the oleoresin were the most toxic compounds followed by O- methylpodocarpic acid, whereas podocarpic acid and tea tree oil showed a lower level of toxicity. On the basis of these findings it is concl uded that an isopropyl group on the aromatic C-ring is of great import ance for the cytotoxicity of the tested abietane resin acids, thus ind icating that the cytotoxic activity of oleoresins most probably is cau sed by synergistic or additive effects of resin acids. The results fro m this work support the view that antibacterial activity parallels cyt otoxic activity which suggests a similar mode of action, most probably exerted by membrane-associated reactions.