Abstract

Complexation behaviour of mixed complexes of mefloquine hydrochloride and chloroquine phosphate (first-line antimalarial drugs) with Cobalt(II), Nickel(II) and Iron(III) were studied; the complexes were prepared using template methods, and chelates of 1:1:1 stoichiometries were formed. The nature of the bonding of the mixed ligands (mefloquine and chloroquine) and structure of the isolated metal complexes were proposed on the basis of their physical and spectroscopic characterization (conductivity measurement, electronic, atomic absorption spectroscopy, magnetic measurements, elemental analysis and infra-red spectroscopy). The complexes in general show 4- and 6-coordinate geometry. The conductivity measurements revealed that all the complexes are non-electrolytes; there was an indication that the mixed ligands were covalently bonded to the metals. In vivo evaluation of the biological studies of the mixed antimalarial metal complexes and free ligands showed greater activity against some of the micro-organisms, when compared to the parent compounds. Toxicological studies revealed that mefloquine, chloroquine and Ni(Mef)(CQ)Cl₂ may have affected the plasma membrane integrity of the cells and were toxic to the tissues, while the mixed metal complexes of mefloquine and chloroquine (Co(Mef)(CQ)Cl₂ and Fe(Mef)(CQ)Cl3) would be a better therapeutic drug for malaria. Our aim is to search for more effective antimalaria drugs.

Key words: Complexation, antimalarial mixed metal complexes, antimicrobial evaluation, toxicological studies.