Antibacterial activity of silver camphorimine coordination polymers

Abstract

Five new silver camphorimine complexes of general formula [Ag(NO3)(Y)L] were synthesized and fully characterized using spectroscopic and analytical techniques. The structure of [Ag(NO3)(OC10H14NC6H4NC10H14O)] () was analyzed using single crystal X-ray diffraction, showing that it arranges as a coordination polymer formed by sequential Ag(NO3) units bridged by the bi-camphor ligand (). The antimicrobial properties of the new complexes were screened using the disk diffusion method and their Minimal Inhibitory Concentrations (MIC) were assessed against selected bacterial strains of the Gram-positive Staphylococcus aureus and the Gram-negative Escherichia coli, Pseudomonas aeruginosa, and Burkholderia contaminans. The lowest MICs were observed for , with estimated values of 72, 20, 32 and 19 μg mL(-1) for S. aureus, E. coli, B. contaminans, and P. aeruginosa, respectively. In the case of S. aureus, similar MIC values were obtained for silver nitrate and compound . All five compounds were bactericidal when used in concentrations equal or above the MIC value, as found by enumerating the total colony forming units (CFUs) after incubation in their presence.

Ag(I) camphorimine complexes with antimicrobial activity towards clinically important bacteria and species of the Candida genus

“…e . the camphorimine ligands binding the silver metal through the nitrogen atom of the camphor imine group and the NO 3 group through two oxygen atoms within a zig-zag polymeric arrangement (Fig 2) as found by X-ray analysis for 5 [28]. …”

“…This way, several camphorimine derivatives were prepared which were used as ligands (Fig 1) to coordinate silver nitrate. The camphor derivatives L I and L III are new, while the other camphor compounds ( L II , L IV —L VIII ) were previously reported [28]. The two new compounds were formulated based on analytical and spectroscopic data (FTIR and NMR).…”

“…The camphor derivatives were synthesized under air using conventional organic synthesis techniques. Complexes ( 4 – 8 ) [28,31] and ligands (L II , L IV -L VIII ) [32,33] were synthesized following published procedures. Camphor, camphorsulfonic acid and the appropriate amines were purchased from Sigma-Aldrich (St. Louis, MO, USA).…”

“…The MIC values were estimated by fitting the OD 640 mean values with a Gompertz modified equation as described before [28]. Mean OD 640 values were obtained from a total of at least 4 experiments from 2 independently prepared MICs assays performed as duplicates.…”

“…Information on the antimicrobial applications of camphor are scarce, although studies showed that camphorimine derivatives have antiviral properties against HIV [26] or influenza virus [27]. In addition, previous results obtained by us on the assessment of the antibacterial activity of camphorimine Ag(I) complexes showed that some have MIC (minimum inhibitory concentration) values considerably lower than AgNO 3 [28]. In this work we have investigated the activity of the three newly synthesized camphorimine Ag(I) complexes 1 – 3 against the ESKAPE members S .…”