Antimalarial activity of ruthenium(II) and osmium(II) arene complexes with mono- and bidentate chloroquine analogue ligands.
Eight new ruthenium and five new osmium p-cymene half-sandwich complexes have been synthesized, characterized and evaluated for antimalarial activity. All complexes contain ligands that are based on a 4-chloroquinoline framework related to the antimalarial drug chloroquine. Ligands HL(1-8) are salicylaldimine derivatives, where HL(1) = N-(2-((2-hydroxyphenyl)methylimino)ethyl)-7-chloroquinolin-4-amine, and HL(2-8) contain non-hydrogen substituents in the 3-position of the salicylaldimine ring, viz. F, Cl, Br, I, NO2, OMe and (t)Bu for HL(2-8), respectively. Ligand HL(9) is also a salicylaldimine-containing ligand with substitutions in both 3- and 5-positions of the salicylaldimine moiety, i.e. N-(2-((2-hydroxy-3,5-di-tert-butylphenyl)methyl-imino)ethyl)-7-chloroquinolin-4-amine, while HL(10) is N-(2-((1-methyl-1H-imidazol-2-yl)methylamino)ethyl)-7-chloroquinolin-4-amine) The half sandwich metal complexes that have been investigated are [Ru(η(6)-cym)(L(1-8))Cl] (Ru-1-Ru-8, cym = p-cymene), [Os(η(6)-cym)(L(1-3,5,7))Cl] (Os-1-Os-3, Os-5, and Os-7), [M(η(6)-cym)(HL(9))Cl2] (M = Ru, Ru-HL(9); M = Os, Os-HL(9)) and [M(η(6)-cym)(L(10))Cl]Cl (M = Ru, Ru-10; M = Os, Os-10). In complexes Ru-1-Ru-8 and Ru-10, Os-1-Os-3, Os-5 and Os-7 and Os-10, the ligands were found to coordinate as bidentate N,O- and N,N-chelates, while in complexes Ru-HL(9) and Os-HL(9), monodentate coordination of the ligands through the quinoline nitrogen was established. The antimalarial activity of the new ligands and complexes was evaluated against chloroquine sensitive (NF54 and D10) and chloroquine resistant (Dd2) Plasmodium falciparum malaria parasite strains. Coordination of ruthenium and osmium arene moieties to the ligands resulted in lower antiplasmodial activities relative to the free ligands, but the resistance index is better for the ruthenium complexes compared to chloroquine. Overall, osmium complexes appeared to be less active than the corresponding ruthenium complexes.
Inorganic Chemistry Research Group, Chemical Physics, Department of Chemistry, Lund University, Box 124, SE-221 00 Lund, Sweden. ebbe.nordlander@chemphys.lu.se.
Erik
E
Ekengard
Lotta
L
Glans
Irwin
I
Cassells
Thibault
T
Fogeron
Preshendren
P
Govender
Tameryn
T
Stringer
Prinessa
P
Chellan
George C
GC
Lisensky
William H
WH
Hersh
Isa
I
Doverbratt
Sven
S
Lidin
Carmen
C
de Kock
Peter J
PJ
Smith
Gregory S
GS
Smith
Ebbe
E
Nordlander
D000818:Animals; D000962:Antimalarials / Q000138:chemical synthesis* / Q000494:pharmacology*; D002738:Chloroquine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000494:pharmacology*; D008024:Ligands; D008958:Models, Molecular; D015394:Molecular Structure; D017892:Osmium Compounds / Q000138:chemical synthesis* / Q000494:pharmacology*; D010963:Plasmodium falciparum / Q000187:drug effects; D017975:Ruthenium Compounds / Q000138:chemical synthesis* / Q000494:pharmacology*; D013329:Structure-Activity Relationship; D014961:X-Ray Diffraction
D000962:Antimalarials; D008024:Ligands; D017892:Osmium Compounds; D017975:Ruthenium Compounds; D002738:Chloroquine