cytotoxic activity of thymus vulgaris, achillea millefolium and thuja orientalis on different growing cell lines

the cytotoxic activity of ethanolic extracts of thymus vulgaris, thuja orientalis and achillea millefolium was investigated on various growing tumor cell lines. mtt colorimetric assay was used for measuring the inhibition of cell proliferation. all of the three extracts showed a relatively dose-dependent inhibition of proliferation of human breast cancer (sk-br-3, mda-mb-435) and leukemia (u937 and k562 ) cell lines. the most sensitive cells to the effect of thuja orientalis and achillea millefolium extracts were k562 and sk-br-3 and to thymus vulgaris were u937 and mda (50% inhibition at 10 µg/ml). hela cell line was less sensitive than other tumor cell lines (% inhibition range -10 to 46). despite this potential cytolytic activity against tumor cell lines, low concentrations of the extracts showed stimulatory effects on the growth ofvero, a non-malignant cell line. proliferation of these cells was increased by 10 to 100 llg/ml of achillea millefolium and thymus vulgaris (%inhibition range -48.8 to -6.25) and suppressed by a concentration of 400 llg/rnl (%inhibition 6.25 and 27.6, respectively). various concentrations of thuja orientalis showed stimulatory effects on this cell line (%inhibition range - 34.00 to -21.4). study of the effect of two low and high concentrations of the extracts on mitogen-induced human lymphocytes resulted in a slight increase at 50 µg/ml (stimulation index, si range 1.19 to 1.37,p<0.01). in conclusion, although the extracts showed strong cytotoxicity for tumor cell lines, the proliferative lymphocytes and the non-malignant cell line used in this study were clearly less sensitive.