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

Abstract

The present work follows a previous report describing the antibacterial activity of silver camphorimine complexes of general formula [Ag(NO3)L]. The synthesis and demonstration of the antifungal and antibacterial activity of three novel [Ag(NO3)L] complexes (named 1, 2 and 3) is herein demonstrated. This work also shows for the first time that the previously studied complexes (named 4 to 8) also exert antifungal activity. The antibacterial activity of complexes was evaluated against Staphylococcus aureus, Pseudomonas aeruginosa, Burkholderia contaminans and Escherichia coli strains, while antifungal activity was tested against the Candida species C. albicans, C. glabrata, C. parapsilosis and C. tropicalis. The antimicrobial activity of the complexes ranged from very high (complex 4) to moderate (complex 6) or low (complex 8), depending on the structural and electronic characteristics of the camphorimine ligands. Notably, the highest antibacterial and anti-Candida activities do not coincide in the same complex and in some cases they were even opposite, as is the case of complex 4 which exhibits a high anti-bacterial and low antifungal activity. These distinct results suggest that the complexes may have different mechanisms against prokaryotic and eukaryotic cells. The antifungal activity of the Ag(I) camphorimine complexes (in particular of complex 1) was found to be very high (MIC = 2 μg/mL) against C. parapsilosis, being also registered a prominent activity against C. tropicalis and C. glabrata. None of the tested compounds inhibited C. albicans growth, being this attributed to the ability of these yeast cells to mediate the formation of less toxic Ag nanoparticles, as confirmed by Scanning Electron Microscopy images. The high antibacterial and anti-Candida activities of the here studied camphorimine complexes, especially of complexes 1 and 7, suggests a potential therapeutic application for these compounds.

Antifungal, Antitumoral and Antioxidant Potential of the Danube Delta Nymphaea alba Extracts

“…MIC values were experimentally determined in a 96 well plate using RPMI 1640 medium (Sigma) containing 20 g/L glucose (final concentration), and buffered to pH 7.0 with 0.165 M morpholine propane sulphonic acid (MOPS; SIGMA) using the broth microdilution method recommended by EUCAST (European Committee on Antimicrobial Susceptibility Testing) for Candida spp. [92], and as previously described [9,93]. The extracts were sequentially 1:2 diluted in order to obtain final concentrations ranging between 0.23 and 2000 µg/mL.…”

Silver Camphor Imine Complexes: Novel Antibacterial Compounds from Old Medicines

“…The catalytic properties of silver complexes have been explored to promote organic transformations and bio-conjugation [ 41 ]. In the last decade, the evaluation of the biological properties of silver complexes has garnered considerable attention, in particular, fostering their use as antimicrobials or anticancer agents [ 1 , 4 , 42 , 43 , 44 , 45 , 46 , 47 ]. The therapeutic uses of silver complexes include silver sulfadiazine for treatment of infections associated with burns.…”

[Ag(L)NO3] Complexes with 2-Benzoylpyridine-Derived Hydrazones: Cytotoxic Activity and Interaction with Biomolecules

“… 7 Silver(I) complexes with different ligands proved to present antimicrobial properties. 8 − 11 In addition, silver(I) complexes have become attractive as anticancer therapeutic drug candidates because of their antiproliferative activity and selectivity against numerous cancer cells. 9 , 12 , 13 …”