Synthesis, Characterization and Antimicrobial properties of Methylbenzyl and Nitrobenzyl containing Imidazolium-based Silver N -Heterocyclic Carbenes

NHCs silver complexes as potential antimicrobial agents

NHCs (N-heterocyclic carbenes) are generally used as organic ligands that can coordinate with metal ions like silver to form stable complexes. These complexes have shown enhanced antimicrobial properties compared to silver alone. This document provides an overview of the reported NHC-based silver derivatives (acetates, chlorides, bromides, and iodides) who possess antimicrobial activity. This review covers articles published between the first report (2006) and 2023.

Surface-Enhanced Raman Scattering (SERS) in Combination with PCA and PLS-DA for the Evaluation of Antibacterial Activity of 1-Isopentyl-3-pentyl-1H-imidazole-3-ium Bromide against Bacillus subtilis

In the current study, surface-enhanced Raman scattering (SERS) was performed to evaluate the antibacterial activity of lab-synthesized drug (1-isopentyl-3-pentyl-1H-imidazole-3-ium bromide salt) and commercial drug tinidazole againstBacillus subtilis. The changes in SERS spectral features were studied for unexposed bacillus and exposed one with various dosages of drug synthesized in the lab (1-isopentyl-3-pentyl-1H-imidazole-3-ium bromide salt), and SERS bands were assigned associated with the drug-induced biochemical alterations in bacteria. Multivariate data analysis tools including principal component analysis (PCA) and partial least-squares discriminant analysis (PLS-DA) have been utilized to analyze the antibacterial activity of the imidazole derivative (lab drug). PCA was employed in differentiating all the SERS spectral data sets associated with the various doses of the lab-synthesized drug. There is clear discrimination among the spectral data sets of a bacterial strain treated with different concentrations of the drug, which are analyzed by PLS-DA with 86% area under the curve in receiver operating curve (ROC), 99% sensitivity, 100% accuracy, and 98% specificity. Various dominant spectral features are observed with a gradual increase in the different concentrations of the applied drug including 715, 850, 1002, 1132, 1237, 1396, 1416, and 1453 cm-1, which indicate the possible biochemical changes caused in bacteria during the antibacterial activity of the lab-synthesized drug. Overall, the findings show that imidazole and imidazolium compounds generated from tinidazole with various alkyl lengths in the amide substitution can be effective antibacterial agents with low cytotoxicity in humans, and these results indicate the efficiency of SERS in pharmaceuticals and biomedical applications.

Structure-Activity Relationships in NHC-Silver Complexes as Antimicrobial Agents

Silver has a long history of antimicrobial activity and received an increasing interest in last decades owing to the rise in antimicrobial resistance. The major drawback is the limited duration of its antimicrobial activity. The broad-spectrum silver containing antimicrobial agents are well represented by N-heterocyclic carbenes (NHCs) silver complexes. Due to their stability, this class of complexes can release the active Ag⁺ cations in prolonged time. Moreover, the properties of NHC can be tuned introducing alkyl moieties on N-heterocycle to provide a range of versatile structures with different stability and lipophilicity. This review presents designed Ag complexes and their biological activity against Gram-positive, Gram-negative bacteria and fungal strains. In particular, the structure-activity relationships underlining the major requirements to increase the capability to induce microorganism death are highlighted here. Moreover, some examples of encapsulation of silver-NHC complexes in polymer-based supramolecular aggregates are reported. The targeted delivery of silver complexes to the infected sites will be the most promising goal for the future.

Coinage Metal N-Heterocyclic Carbene Complexes: Recent Synthetic Strategies and Medicinal Applications

New weapons are constantly needed in the fight against cancer. The discovery of cisplatin as an anticancer drug prompted the search for new metal complexes. The successful history of cisplatin motivated chemists to develop a plethora of metal-based molecules. Among them, metal-N-heterocyclic carbene (NHC) complexes have gained significant attention because of their suitable qualities for efficient drug design. The enhanced applications of coinage metal-NHC complexes have encouraged a gradually increasing number of studies in the fields of medicinal chemistry that benefit from the fascinating chemical properties of these complexes. This review aims to present recent developments in synthetic strategies and medicinal applications of copper, silver and gold complexes supported by NHC ligands.

N-heterocyclic carbene-metal complexes as bio-organometallic antimicrobial and anticancer drugs, an update (2015–2020)

N-heterocyclic carbenes (NHCs) are organic compounds that typically mimic the chemical properties of phosphines. NHCs have made a significant impact on the field of coordination and organometallic chemistry because they are easy to prepare and handle and because of their versatility and stability. Importantly, the physicochemical properties of NHCs can be easily fine-tuned by simple variation of substituents on the nitrogen atoms. Over the past few years, various NHC–metal complexes have been extensively used as metal-based drug candidates and catalysts (homogeneous or heterogeneous) for various applications. To help assist future work with these compounds, this review provides a thorough review on the latest information involving some biomedical applications of NHC–metal complexes. Specifically, this article focuses on recent advances in the design, synthesis, characterization and biomedical applications (e.g., antimicrobial and anticancer activity) of various NHC–metal complexes (metal: silver, gold, palladium, rhodium, ruthenium, iridium and platinum) covering work published from 2015 to 2020. It is hoped that the promising discoveries to date will help accelerate studies on the encouraging potential of NHC–metal complexes as a class of effective therapeutic agents.