Preparation, characterization, and the selective antimicrobial activity of N-alkylammonium 8-diethyleneglycol cobalt bis-dicarbollide derivatives

A consistent series of N-alkylammonium derivatives of 8-diethyleneglycol-Co-III-bisdicarbollide has been prepared via straightforward method, and characterized using NMR, HPLC, MS and X-ray. The structure of the most stable dimethylammonium zwitterion 5 was verified by the XRD. The antibacterial, and antifungal activity of the seven studied derivatives was found based on the determination of minimum inhibitory concentrations (MIC80). The growth of the Staphylococcus aureus, the most common isolated from nosocomial infections, was inhibited with high selectivity by compound 3 in concentration 3.8 mg L-1. A significant observation was the absolute selective activity of 4 in inhibiting the growth of the filamentous fungus Trichosporon cutaneum. The high selectivity and the lowest MIC80 concentrations of the designed inhibitors allow generally to decrease the number of possible side effects usually occurred during medical treatment of the specific pathogen. Our results provide a new knowledge about the possible use of metallacarboranes as antimicrobial agents; this subject is highly topical due to the emerging antibiotic resistance of a number of pathogenic microorganisms of high concern. (C) 2016 Elsevier B.V. All rights reserved.