Half-Sandwich Cyclopentadienylruthenium(II) Complexes: A New Antimalarial Chemotype

Inorg Chem. 2020 Sep 8;59(17):12722-12732. doi: 10.1021/acs.inorgchem.0c01795. Epub 2020 Aug 24.

Abstract

A small library of "half-sandwich" cyclopentadienylruthenium(II) compounds of the general formula [(η5-C5R5)Ru(PPh3)(N-N)][PF6], a scaffold hitherto absent from the toolbox of antiplasmodials, was screened for activity against the blood stage of CQ-sensitive 3D7-GFP, CQ-resistant Dd2, and artemisinin-resistant IPC5202 Plasmodium falciparum strains and the liver stage of Plasmodium berghei. The best-performing compounds displayed dual-stage activity, with single-digit nanomolar IC50 values against blood-stage malaria parasites, nanomolar activity against liver-stage parasites, and residual cytotoxicity against HepG2 and Huh7 mammalian cells. The parasitic absorption/distribution of 7-nitrobenzoxadiazole-appended fluorescent compounds Ru4 and Ru5 was investigated by confocal fluorescence microscopy, revealing parasite-selective absorption in infected erythrocytes and nuclear accumulation of both compounds. The lead compound Ru2 impaired asexual parasite differentiation, exhibiting fast parasiticidal activity against both ring and trophozoite stages of a synchronized culture of the P. falciparum 3D7 strain. These results point to cyclopentadienylruthenium(II) complexes as a highly promising chemotype for the development of dual-stage antiplasmodials.

MeSH terms

  • Antimalarials / chemistry*
  • Antimalarials / pharmacology*
  • Coordination Complexes / chemistry*
  • Coordination Complexes / pharmacology*
  • Cyclopentanes / chemistry*
  • Drug Resistance / drug effects
  • Erythrocytes / drug effects
  • Hep G2 Cells
  • Humans
  • Oxadiazoles / chemistry
  • Plasmodium berghei / drug effects
  • Plasmodium falciparum / drug effects
  • Ruthenium / chemistry*

Substances

  • Antimalarials
  • Coordination Complexes
  • Cyclopentanes
  • Oxadiazoles
  • Ruthenium