Spectral properties and biological activity of La(III) and Nd(III) Monensinates

The present research is focused on evaluation of complexation ability of Monensic acid (MonH) towards La3+ and Nd3+ ions. Changes in the SRCD spectrum of Monensinate anion were monitored upon addition of lanthanide(III) ions. The antibiotic undergoes formation of one neutral ([Ln(Mon)(3)(H2O)(3)]) and two positively charged complex species of composition [Ln(Mon)(2)(H2O)(2)](+) and [Ln(Mon)(2)(H2O)](2+), respectively (Ln = La3+, Nd3+). Neutral complexes were isolated as fine powders and were characterized by IR, FAB-MS and ESI-MS. It is assumed that Monensin acts in bidentate coordination mode via monodentate carboxylate moiety and hydroxyl group, both located at the opposite ends of antibiotic molecule. Activity of Monensic acid and [Ln(Mon)(3)(H2O)(3)] to decrease visible bacteria growth of B. subtilis, S. Lutea and B. mycoides was evaluated by agar hole diffusion method. Results showed that complexation of lanthanide(III) ions to Monensin enhances the activity of non-coordinated ligand. Antitumor efficacy of compounds was assayed on human triple negative breast cancer and transplantable sarcoma in rat. The cytotoxicity was accessed by MTT test, NR uptake, CV assay and double AO/PI staining. Experimental data revealed that Monensic acid and [Ln(Mon)(3)(H2O)(3)] possess concentration- and time-dependent activity, and express promising cytotoxic properties against human and rat permanent cancer cell lines.