| In order to optimize the antileishmanial activity of piperazinyl-linked 5-(5-nitrofuran-2-yl)-1,3,4-thiadiazoles,
we synthesized a series of 5-(5-nitrofuran-2-y1)-1,3,4-thiadiazoles with piperazinyl-linked
benzamidine substituent as scaffold found in pentamidine related antiprotozoals. The structure of target
compounds was confirmed by IR,
1
H NMR,
13
C NMR and Mass spectral data. All compounds were tested
for in vitro activity against the promastigote and amastigote forms of Leishmania major. From the results,
we found that the substitution on amidine nitrogen has profound role in the biological activity of these
compounds. The 5-nitrofuran-2-yl-1,3,4-thiadiazoles having n-propyl, n-butyl and benzyl side chain on
benzamidine (as in compounds 2d, 2e and 2g, respectively) showed very good activity in both forms of
promastigote and amastigote. The most active compound was N-propyl-4-(4-(5-(5-nitrofuran-2-yl)1,3,4-thiadiazol-2-yl)piperazin-1-yl)
benzamidine hydrochloride (2d) with IC
value of 0.08 mMin
promastigote model. This compound showed a very low level of toxicity against macrophages
(CC
50
50
¼ 785 mM), with the highest selectivity index (SI ¼ 78.5) among the tested comp |