Synthesis, Characterization, Antimicrobial Properties, and Antioxidant Activities of Silver-N-Heterocyclic Carbene Complexes

by Selleckchem | Sep 01 2023

The emergence of antimicrobial resistance has become a major handicap in the fight against bacterial infections, prompting researchers to develop new, more effective, and multimodal alternatives. Silver and its complexes have long been used as antimicrobial agents in medicine because of their lack of resistance to silver, their low potency at low concentrations, and their low toxicity compared to most commonly used antibiotics. N-Heterocyclic carbenes (NHCs) are widely used for coordination of transition metals, mainly in catalytic chemistry. In this study, several N-alkylated benzimidazolium salts 2a-j were synthesized. Then, the N-heterocyclic carbene (NHC) precursor was treated with Ag2O to give silver (I) NHC complexes (3a-j) at room temperature in dichloromethane for 48 h. Ten new silver-NHC complexes were fully characterized by nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR), elemental analysis, and LC-MSMS (for complexes) techniques. The antibacterial and antioxidant activities of salt 2 and its silver complex 3 were evaluated. All of these complexes were more effective against bacterial strains than comparable ligands. With MIC values ranging from 6.25 to 100 g/ml, the Ag-NHC complex effectively showed strong antibacterial activity. Antioxidant activity was also tested using conventional techniques, such as 2, 2-diphenyl-1-picrylhydrazine (DPPH) and hydrogen peroxide scavenging assays. In DPPH and ABTS experiments, compounds 3a, 3b, 3c, 3e, 3g, and 3i showed significant clearance.

Comments:

The study you mentioned focuses on the development and characterization of new silver-NHC complexes as antimicrobial agents. Antimicrobial resistance has become a significant challenge in combating bacterial infections, leading researchers to explore alternative strategies. Silver and its complexes have been used in medicine due to their low toxicity, lack of resistance development, and effectiveness against various bacteria.

The researchers synthesized N-alkylated benzimidazolium salts (2a-j) and then treated the N-heterocyclic carbene (NHC) precursor with Ag2O to obtain silver (I) NHC complexes (3a-j) under specific conditions. The synthesized complexes were thoroughly characterized using techniques such as nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR), elemental analysis, and LC-MSMS.

The antibacterial and antioxidant activities of both the benzimidazolium salts (2) and their corresponding silver complexes (3) were evaluated. The results showed that the silver-NHC complexes exhibited superior antibacterial activity compared to the corresponding ligands. The minimum inhibitory concentration (MIC) values of the complexes ranged from 6.25 to 100 g/ml, indicating strong antibacterial efficacy.

Additionally, the antioxidant activity of the complexes was assessed using conventional techniques like 2,2-diphenyl-1-picrylhydrazine (DPPH) and hydrogen peroxide scavenging assays. Compounds 3a, 3b, 3c, 3e, 3g, and 3i demonstrated significant antioxidant activity in the DPPH and ABTS experiments.

Overall, this study highlights the successful synthesis and characterization of novel silver-NHC complexes with potent antibacterial and antioxidant properties. These findings contribute to the ongoing efforts in developing effective antimicrobial agents and expanding our understanding of the potential applications of silver complexes in medicine.