The curves of the growth inhibition percentages after 24 h treatment with different concentrations of TOPO in the absence or presence of a fixed concentration of carvacrol (166 µM)) in (A) HeLa, (B) HCT116, (C) MCF-7, (D) HepG2, (E) SKOV3 and (F) A549 cell lines. Data were expressed as mean ± SD (error bars), n = 3. The significant differences between TOPO and (TOPO + carvacrol (166 µM)) combination at each time assessed by mesuring the P-values using the independent t-test, were classified to * P < 0.05, ** P < 0.01 and *** P < 0.001.