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Preparation of solutions: Stock solutions (10 mg [ml.sup.-1]) of L-tryptophan, nicotinic acid, picolinic acid and nicotinamide were prepared in water, and benznidazole and nifurtimox were prepared in 10% DMSO (v [v.sup.-1]).
Antitrypanosomal activity: Epimastigotes of M5-2 strain in logarithmic growth phase (5 x [10.sup.5] cells) were added to 18 x 180 mm screw-capped tubes containing 2 mL of growth medium with 10 or 50 [micro]g [ml.sup.-1] picolinic acid added.
The medium containing different concentrations of picolinic acid (1200 - 1.12 [micro]g [ml.sup.-1]) were added to each well containing the cells, and the plates were incubated for 96h.
Effect of L-tryptophan, nicotinic acid and nicotinamide on picolinic acid inhibitory activity: The experiments using epimastigote and trypomastigote forms were performed as above, except that L-tryptophan, nicotinic acid and nicotinamide were added (100 [micro]g [ml.sup.-1] final concentration) aseptically to the growth medium or phosphate buffer containing 50 [micro]g [ml.sup.-1] picolinic acid.
In this study, we also examined the effect of picolinic acid on the growth of epimastigote forms and the motility of trypomastigote forms of M5-2 strain of Schizotrypanum trypanosomes isolated from bat Phyllostomus hastatus.
The number of motile trypomastigotes decreased (50%) after 6h in the presence of 50 [micro]g [ml.sup.-1] picolinic acid, and after 24h no motile trypomastigotes were observed.