en بیوشیمی Biochemistry مقالات اصلی Original Article <div style="text-align: justify;"><strong><em>Background:</em></strong> Some recent studies have reported anti-tumor activity for Thymol, but the findings are inconsistent. This study aimed to investigate and compare Thymol&#39;s effects on MCF-7 cancer cells and fibroblasts while treated with tert-Butyl hydroperoxide (t-BHP).<br> <br> <strong><em>Methods:</em></strong> In the pre-treatment, MCF-7 and fibroblast cells were treated with various Thymol concentrations and incubated for 24 h. Then, t-BHP was added to a final concentration of 50 &mu;M, and the cells were incubated for one h. In the post-treatment, cells were incubated first with 50 &mu;M t-BHP for one h and then treated with Thymol. Cell viability was tested by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Thymol&#39;s antioxidant capacity was measured by DPPH and FRAP assays, and lipid peroxidation levels were determined by the TBARS method.<br> <br> <strong><em>Results:</em></strong> The thymol effects were dose-dependent, and despite their antioxidant properties, at concentrations of 100 &micro;g/ml or more, increased t-BHP toxicity and reduced cancer cell viability. MTT assay result showed that pre-treatment and post-treatment with Thymol for 24 hours effectively reduced MCF-7 and fibroblast cell viability compared with the untreated control group. Both pre- and post-treatment of Thymol, normal fibroblast cell viability was significantly greater than that of the MCF-7 cells.<br> <br> <strong><em>Conclusions:</em></strong> Our finding showed that Thymol appears to be toxic to MCF-7 cells at lower concentrations than fibroblasts after 24 hours of incubation. Pre-treatment with Thymol neutralized the oxidative effect of t-BHP in fibroblasts but was toxic for MCF-7 cells.</div> Breast Cancer, MCF-7 Cells, Oxidative Stress, tert-Butyl Hydroperoxide, Thymol. 338 347 http://rbmb.net/browse.php?a_code=A-10-517-1&slc_lang=en&sid=1 Afsaneh Dashtaki 100319475328460017686 100319475328460017686 No Student Research Committee, Babol University of Medical Sciences, Babol, I. R. Iran & Department of Clinical Biochemistry, School of Medicine, Babol University of Medical Sciences, Babol, I. R. Iran Soleiman Mahjoub s.mahjoub@mubabol.ac.ir 100319475328460017687 100319475328460017687 Yes Cellular and Molecular Biology Research Center, Health Research Institute, Babol University of Medical Sciences, Babol, I. R. Iran & Department of Clinical Biochemistry, School of Medicine, Babol University of Medical Sciences, Babol, I. R. Iran. Ebrahim Zabihi 100319475328460017688 100319475328460017688 No Cellular and Molecular Biology Research Center, Health Research Institute, Babol University of Medical Sciences, Babol, I. R. Iran Roghayeh Pourbagher 100319475328460017689 100319475328460017689 No Cellular and Molecular Biology Research Center, Health Research Institute, Babol University of Medical Sciences, Babol, I. R. Iran