en تخصصي Special پژوهشي Research <strong>Background:</strong> Breast cancer is a common human neoplasia in women. Species of the Lamiaceae plant have been found to exert in vitro anti-proliferative activity on breast cancer cells. The aim of this study was to evaluate the cytotoxic effect of the extracts of ten species from the Lamiaceae family on a breast cancer cell line. We also examined the selective indices of the fractions and essential oil of the most effective extract.<br> <strong>Methods:</strong> The plant species were harvested, dried and authenticated. The hydro-alcoholic extract of each plant was examined for its cytotoxicity on the breast cancer cell line (MCF-7) using MTT assay. The n-Hexane, chloroform and ethyl acetate fractions were prepared from Nepeta crispa extract. Hydro-distillation method was used to isolate the Nepeta crispa&rsquo;s essential oil. The essential oil and the fractions were examined in vitro for the cytotoxic effects against both HEK293 and MCF-7 cell lines.<br> <strong>Results:</strong> The Nepeta crispa extract exhibited significant cytotoxic activity on MCF-7 (IC50 = 59 &plusmn;3.4&mu;g/mL) compared to other extracts. The n-hexane fraction of Nepeta crispa demonstrated the highest cytotoxicity (IC50 = 65.47 &plusmn;4.3&mu;g/mL) among other fractions. The essential oil exhibited concentration-dependent inhibition against the growth of cancer cells, and showed the most inhibitory effect against MCF-7 cells (IC50 = 18.15 &plusmn;2.7&mu;g/mL) with a selectivity index of 9.69.<br> <strong>Conclusions:</strong> Based on the results, the n-hexane fraction and essential oil of Nepeta crispa may be the potential sources of biologically active components to develop novel drugs for breast cancer treatment. Cancer, MTT assay, Nepeta crispa, Essential oil, Extract, Fraction 35 41 http://ijt.arakmu.ac.ir/browse.php?a_code=A-10-1127-1&slc_lang=en&sid=1 Azadeh Vali nasimvl@yahoo.com 100319475328460015139 0009-0003-1817-2687 No Department f Pharmacognosy, School of Pharmacy, Medicinal Plants and Natural Product Research Center, Hamadan University of Medical Sciences, Hamadan, Iran Meysam Soleimani Badie meysambadia@yahoo.com 100319475328460015140 100319475328460015140 No Department f Pharmaceutical Biotechnology, School of Pharmacy, Hamadan University of Medical Sciences, Hamadan, Iran Dara Dastan d.dastan@umsha.ac.ir 100319475328460015141 100319475328460015141 No Department f Pharmacognosy, School of Pharmacy, Medicinal Plants and Natural Product Research Center, Hamadan University of Medical Sciences, Hamadan, Iran Shirin Moradkhani shirin.moradkhani@yahoo.com 100319475328460015142 100319475328460015142 Yes Department f Pharmacognosy, School of Pharmacy, Medicinal Plants and Natural Product Research Center, Hamadan University of Medical Sciences, Hamadan, Iran