evaluation of some iranian conifers extracts cytotoxicity, using sacharomyces cerevisiae, rs 322n and rs 188n

exploration of natural products with antitumoral effects such as etoposide, tenioposide, camptothecin and paclitaxel from conifers provoked us to do some research on anti-tumoral activity of iranian medicinal plants. ten different species of iranian conifers aerial parts were collected across the country. the relative potency of methanolic extract were investigated on the inhibition of topoisomerase i on yeasts (sacharomyces cerevisiae, rs 322n and s. cerevisiae, rs 188n, as wild type) using agar diffusion, turbidimetry and agar dilution procedures. briefly, 0.1 ml of extracts (20 mg/ml) were added to the yeast culture and the obtained zone of inhibition were evaluated compare to the control (camptothecin, 2 μg/ml). zones of inhibition >12 mm on mutant type and no inhibition effect on wild type were considered as positive results or cytotoxicity. for agar dilution assay, different dilutions of extracts (5, 10, 20, 40, 80 mg/ml) were applied and inhibition of yeast growth was considered as positive result. in turbidimetric assay no turbidity was evaluated as cytotoxicity. minimum inhibitory concentration was determined by agar dilution and turbidimetric procedures. to determine minimum biocidal concentration, samples were transferred from turbidimetric cells to solid media. according to the agar diffusion results, none of the extracts showed specific cytotoxicity on mutant yeast. the results obtained from growth inhibition of platycladus orientalis extracts were shown to have some good cytotoxic effects on both mutant and wild type. in conclusion, agar dilution and turbidimetry results were similar according to the high concentration of extracts and this means that the cytotoxic effects of these plants on yeasts are not specific.