title: Experimental conditions for testing the inhibitory activity of chloroquine on the formation of beta-hematin.
abstract: Some antimalarial drugs act by inhibiting the process of ferriprotoporphyrin IX polymerization which protects the parasite against the noxious effect of this product of host cell hemoglobin digestion. As the quest for new drugs with a similar mode of action continues, high-throughput screening methods are needed. We demonstrate herein that such a recently described screening technique (Basilico et al., J. Antimicrob. Chemother. 42, 55-60, 1998) is considerably disturbed by certain ions. Thus, at the assay's pH 2.6, the phosphate ions are responsible for the inhibitory activity of chloroquine phosphate, rather than chloroquine itself. Using a combination of solubility tests and Fourier transform infrared spectrometry we also show that two alternative methods using higher pH's are also prone to salt effects and demonstrate that these can be minimized by extensive washing of the product with DMSO.
authors.affiliation: Instituto Boliviano de Biologia de Altura (IBBA), Casilla 717, La Paz, Bolivia.
authors.forename: R
authors.initials: R
authors.lastname: Baelmans
authors.forename: E
authors.initials: E
authors.lastname: Deharo
authors.forename: V
authors.initials: V
authors.lastname: Muñoz
authors.forename: M
authors.initials: M
authors.lastname: Sauvain
authors.forename: H
authors.initials: H
authors.lastname: Ginsburg
mesh_terms: D000962:Antimalarials / Q000737:chemistry / Q000494:pharmacology*; D002712:Chlorides / Q000494:pharmacology; D002738:Chloroquine / Q000737:chemistry / Q000494:pharmacology*; D006420:Hemeproteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D010710:Phosphates / Q000494:pharmacology; D012995:Solubility; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D000962:Antimalarials; D002712:Chlorides; D006420:Hemeproteins; D010710:Phosphates; C020753:hemozoin; D002738:Chloroquine