The cytotoxicity of compounds 1-11 against the normal MRC-5 cell line (Table 1(Tab. 1)) was previously documented (Prachayasittikul et al., 2014). Moderately active compounds 2 and 10 and inactive compound 11 were shown to be non-cytotoxic. It should be noted that both of the highly active aromatase inhibitors (1 and 4) exhibited a high safety index with selectivity index values of 45.98 and 17.20, respectively. However, compound 4 displayed higher cytotoxicity than compound 1.