In this research, the chemical structure of curcumin was modified by derivatization reaction. Modification of the curcumin was performed by derivatization with nicotinoyl chloride. The condensation of this molecule with curcumin produced a new ligand with a higher solubility and stability than curcumin. The new bridging ligand possesses two pyridine groups for metal bonding and complex formation. After modification of the curcumin structure, the product was characterized by FT-IR, UV-Vis, NMR, and MS. Then this new bridging ligand was used to synthesis of dinuclear complexes of copper and zinc, [Cu 2 (Terpy) 2 (CH 3 CN) 2 - m -Cur-Nic](NO 3 ) 4 and [Zn 2 (Terpy) 2 (CH 3 CN) 4 - m -Cur-Nic](NO 3 ) 4 . These complexes were characterized by FT-IR, UV-Vis, and elementral analysis. The toxicity effects of all compounds on the MCF-7 (breast cancer cell line) and MCF-10A (healthy breast cell line) were investigated by the MTS assay. Moreover, the antibacterial effect of all compounds on the Methicillin-resistant Staphylococcus aureus bacteria (MRSA) was assessed by the Broth Dilution method. The calculated IC 50 (minimum concentration for killing 50% of cells) and MIC (minimum concentration for killing bacteria) were calculated for the compounds. According to the results, the toxicity of Cur-Nic was decreased in both cell lines, whereas its positive feature was the increasing selectivity between the cancer cells and the healthy one compared to the pure curcumin. Also, the coordination of Cu (II) and Zn (II) to Cur-Nic increases the cytotoxicity, but this increase is lower for healthy cells than for the cancer cells. The IC 50 values calculated for the compounds were as follows: 9.37 for dinuclear Cu complex, and more than 50 ?M for dinuclear Zn complex against MCF-7 cells, as well as 50 and 100 ?M for dinuclear Cu and Zn complexes against the MCF-10A cell lines, respectively. The results indicate that the selectivity of curcumin and Cur-Nic between the normal and cancerous cells is increased due to the complexation. The effect of the substances on MRSA is as follows: by increasing the drug concentration, the bacterial viability increases, indicating the increase of the drug resistance. The MIC obtained for the dinuclear copper complex was 0.01 ?M, which is better than that of the curcumin MIC (0.67 ?M). The MIC values of Cur-Nic and dinuclear zinc complex were not achieved in the measured concentration range because they are not been able to completely inhibit the bacterial growth.
