title: Synergism of desbutyl-benflumetol and retinol against Plasmodium falciparum in vitro.
abstract: This in vitro study was conducted to assess the blood schizontocidal activity of desbutyl-benflumetol (DBB), a new benzindene derivative, retinol and a combination of both compounds. The tests were carried out according to the methodology of the WHO standard test Mark II, measuring the drug-dependent inhibition of schizont maturation, and using 43 fresh isolates of Plasmodium falciparum from northwestern Thailand, an area with established multidrug-resistance. DBB and retinol showed a mean 50% effective concentration (EC-50) of 3.73 nM and 466.86 nM and 90% effective concentration (EC-90) of 19.83 nM and 5531.69 nM respectively. The combination of DBB and 3.50 muM retinol showed strong inhibition of schizont maturation, with an EC-90 for DBB of 0.67 nM. At the therapeutically relevant EC-99, the combination was about 10 times more effective than expected, suggesting that retinol potentiated the effect of DBB. A concentration of 3.50 muM retinol corresponds to the 95th percentile of the physiological serum levels. It is well known that retinol levels are significantly decreased in acute falciparum malaria. Supplementation with retinol during malaria treatment may improve the therapeutic results of blood schizontocides of the fluorene class.
authors.affiliation: Department of Neurology, Medical University of Vienna, Vienna, Austria. doris.samal@meduniwien.ac.at
authors.forename: Doris
authors.initials: D
authors.lastname: Samal
authors.forename: Chaiporn
authors.initials: C
authors.lastname: Rojanawatsirivet
authors.forename: Gunther
authors.initials: G
authors.lastname: Wernsdorfer
authors.forename: Herwig
authors.initials: H
authors.lastname: Kollaritsch
authors.forename: Jeeraphat
authors.initials: J
authors.lastname: Sirichaisinthop
authors.forename: Walther H
authors.initials: WH
authors.lastname: Wernsdorfer
mesh_terms: D000818:Animals; D000962:Antimalarials / Q000008:administration & dosage; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D004351:Drug Resistance; D004357:Drug Synergism; D004983:Ethanolamines / Q000008:administration & dosage*; D005449:Fluorenes / Q000008:administration & dosage*; D006801:Humans; D016778:Malaria, Falciparum / Q000097:blood / Q000175:diagnosis / Q000188:drug therapy* / Q000469:parasitology*; D021261:Parasitic Sensitivity Tests; D010963:Plasmodium falciparum / Q000166:cytology / Q000187:drug effects* / Q000302:isolation & purification*; D016896:Treatment Outcome; D014801:Vitamin A / Q000008:administration & dosage*; D014815:Vitamins / Q000008:administration & dosage
chemical_list: D000962:Antimalarials; D004338:Drug Combinations; D004983:Ethanolamines; D005449:Fluorenes; D014815:Vitamins; C435716:desbutylbenflumetol; D014801:Vitamin A