Synergetic Antimicrobial Activity and Mechanism of Clotrimazole-Linked CO-Releasing Molecules

Sofia S. Mendes, Joana Marques, Edit Mesterházy, Jan Straetener, Melina Arts, Teresa Pissarro, Jorgina Reginold, Anne Berscheid, Jan Bornikoel, Robert M. Kluj, Christoph Mayer, Filipp Oesterhelt, Sofia Friães, Beatriz Royo, Tanja Schneider, Heike Brötz-Oesterhelt, Carlos C. Romão, Lígia M. Saraiva

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)


Several metal-based carbon monoxide-releasing molecules (CORMs) are active CO donors with established antibacterial activity. Among them, CORM conjugates with azole antibiotics of type [Mn(CO)3(2,2′-bipyridyl)(azole)]+ display important synergies against several microbes. We carried out a structure-activity relationship study based upon the lead structure of [Mn(CO)3(Bpy)(Ctz)]+ by producing clotrimazole (Ctz) conjugates with varying metal and ligands. We concluded that the nature of the bidentate ligand strongly influences the bactericidal activity, with the substitution of bipyridyl by small bicyclic ligands leading to highly active clotrimazole conjugates. On the contrary, the metal did not influence the activity. We found that conjugate [Re(CO)3(Bpy)(Ctz)]+ is more than the sum of its parts: while precursor [Re(CO)3(Bpy)Br] has no antibacterial activity and clotrimazole shows only moderate minimal inhibitory concentrations, the potency of [Re(CO)3(Bpy)(Ctz)]+ is one order of magnitude higher than that of clotrimazole, and the spectrum of bacterial target species includes Gram-positive and Gram-negative bacteria. The addition of [Re(CO)3(Bpy)(Ctz)]+ to Staphylococcus aureus causes a general impact on the membrane topology, has inhibitory effects on peptidoglycan biosynthesis, and affects energy functions. The mechanism of action of this kind of CORM conjugates involves a sequence of events initiated by membrane insertion, followed by membrane disorganization, inhibition of peptidoglycan synthesis, CO release, and break down of the membrane potential. These results suggest that conjugation of CORMs to known antibiotics may produce useful structures with synergistic effects that increase the conjugate's activity relative to that of the antibiotic alone.

Original languageEnglish
Pages (from-to)419-436
Number of pages18
JournalACS Bio and Med Chem Au
Issue number4
Publication statusPublished - 17 Aug 2022


  • antimicrobials
  • carbon monoxide
  • carbon monoxide-releasing molecules
  • lipid II
  • membrane depolarization
  • peptidoglycan synthesis inhibition
  • Staphylococcus aureus


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