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

Abstract

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.

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

“…The lipophilicity is increased by the bulky substituents, which leads to enhance their antimicrobial potential. 7 Different aromatic heterocyclic compounds have been employed for a variety of bioactive chemicals including antimicrobials, antifungal, anticancer, and antidiabetic agents. 8−10 In medicinal chemistry, the search for novel and powerful imidazole-derived bioactive drugs continues to be a major focus.…”

“…Even if the exact process causing bacterial cell damage is still not fully understood, several hypotheses are reported in the literature, and the most important is that the lipophilicity of these compounds causes a change in membrane permeability. The lipophilicity is increased by the bulky substituents, which leads to enhance their antimicrobial potential …”