Antimicrobial Activity of Copper (II) Complex with 1,2-bis ((1,3-diphenylpyrazol-4-yl)methyl) Diaminoethane

Background: Multi-resistant strains multiply daily, populate farms, hospitals and other ecological niches around the world, and cause serious infections in animals and humans, often leading to a fatal outcome. Researchers of all profi les are investigating intensively to finew substances with antimicrobial activity. In the period between 1981 and 2002, 163 new chemical compounds were approved for use as drugs. Synthesized compounds have become much more interesting than the natural ones in the production of new antimicrobial agents. Some of these synthesized compounds are Copper (II) complex. The antimicrobial properties of copper were known in ancient Egypt (2000 BC), where it was used to sterilize water and wounds. Copper is still interesting for today’s research. Materials, Methods & Results: Antimicrobial activity was tested using a microdilution method according to Clinical and Laboratory Standards Institute. The percentage of surviving bacteria was calculated in comparison to the number of bacteria placed in each well. Based on these results, using the Excel software package from Microsoft Offi ce 2007, graphs were generated that showed the percentage of surviving bacteria depending on the corresponding effective concentrations of the tested substance. The function, which was used to approximate the experimental results, was determined using the Power Trendline supplement from the Microsoft Excel program. Cytotoxicity (growth inhibition) was evaluated by tetrazolium colorimetric MTT assay, after exposure of cells to the tested compound for 48 h. Inhibition of growth was expressed as a percentage of cytotoxicity and calculated according to the following equation: (1-A test/A control) x 100. MBC 99.9 and MIC 99 of the test substance were lowest for Arcanobacterium haemolyticum being 0.2 mg/L and 0.0054 mg/L, respectively. The highest values were obtained for Arcanobacterium pyogenes and methicillin-resistant Staphylococcus aureus (MRSA) 488.002 mg/L and 20.2 mg/L. MIC 80 for all four strains ranged from 0.00002 to 0.0023 mg/L. Measured values for MIC 99 are 0.00545 mg/L for A. haemolyticum, 0.0443199 mg/L for R. equi, 0.0520712 mg/L for S. aureus and 2.36378 mg/L for A. pyogenes. Values for MIC 99.9 ranged from 0.236134 to 488,002 mg/L. Most of the MIC values obtained in this study are signifi cantly lower than those reported by other researchers. The values we obtained were lower as compared to MIC values for standard antibiotics, which were considered acceptable by the relevant institutions. This speaks in favor of a stronger antibacterial effect of our tested substances. In regards to cytotoxicity, the obtained MIC 80 doses were lower than toxic, whereas MIC 90 could be classifi ed as low-toxic (less than 0.0625 µM), except of Arcanobacterium pyogenes only. According to the IC50 values, the compound Cu (L) Br2·MeOH was 6.4-fold and 4.8-fold more potent against HCT116 cells compared to normal lung fi broblasts and SW620 cells, respectively. Discussion: Copper (II) complex with an arylpyrazole ligand exhibits strong antibacterial properties, and it shows bacteriostatic effect at concentrations where there is no cytotoxic effect in normal human cells. The emergence of multi-resistant strains of pathogenic bacteria is a growing problem worldwide. Therefore, each new compound with potential antimicrobial activity, especially if it is not cytotoxic in effective dosage, deserves the attention of the scientifi c community. In this paper, we presented a newly synthesized substance with such properties.