Determination of anti-giardial activity in vitro by means of soluble formazan production.
A new microplate assay for the determination of activity in vitro against Giardia intestinalis has been developed in which viability is measured by soluble formazan production from a tetrazolium reagent. Metabolic reduction of the latter gives rise to a coloured product which may be determined directly by optical density measurement. Using this method the anti-giardial activities of more than 20 anti-microbial compounds have been assessed. The results obtained with a number of known anti-giardial agents, including metronidazole (50% inhibitory concentration [IC50] = 2.98 microM) and furazolidone (IC50 = 4.14 microM), compare well with previously published data; mepacrine, however, was found to produce a biphasic dose-response curve from which two IC50 values (0.816 and 6.83 microM) were obtained. This method provides a convenient means by which the search for new anti-giardial agents may be facilitated.
Wright
C W
CW
Department of Pharmacognosy, School of Pharmacy, Brunswick Square, London, UK.
Melwani
S I
SI
Phillipson
J D
JD
Warhurst
D C
DC
D000818:Animals; D000981:Antiprotozoal Agents / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005562:Formazans / Q000378:metabolism*; D016829:Giardia lamblia / Q000187:drug effects / Q000378:metabolism*; D010274:Parasitology / Q000379:methods; D013778:Tetrazolium Salts / Q000378:metabolism*
D000981:Antiprotozoal Agents; D005562:Formazans; D013778:Tetrazolium Salts; C059087:2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-((phenylamino)carbonyl)-2H-tetrazolium hydroxide