Thio- and selenosemicarbazones as antiprotozoal agents against Trypanosoma cruzi and Trichomonas vaginalis

Figures & data

Figure 1. General structure for the ntiprotozoal thio(seleno)semicarbazones prepared herein.

Scheme 1. Preparation of thiosemicarbazones 36‒65.

Scheme 2. Preparation of selenosemicarbazones 72, 73.

Table 1. In vitro activity against Trypanosoma cruzi CL-B5 (DTU TcVI) and Y (DTU TcII) parasites and unspecific cytotoxicity on L929 and J774 cells, expressed as IC₅₀ and CC₅₀ values, respectively. Selectivity indexes (SI) for each strain and form are also calculated.

Compound	IC50 (µM)^a CL-B5 epimastigotes	CC50 (µM)^a L929 cells	SI^b CL-B5 epi	IC50 (µM)^a Y epimastigotes	CC50 (µM)^a J774 cells	SI^b Y epi	IC50 (µM)^a CL-B5 amastigotes	SI^b CL-B5 ama
23 (R^1=OMe, R^2=R^3=H)	53.51 ± 12.98	>256	>4.78	59.91 ± 10.43	>256	>4.27	−	−
24 (R^1=F, R^2=R^3=H)	58.80 ± 8.77	>256	>4.35	97.26 ± 3.45	>256	>2.63	−	−
25 (R^1=Cl, R^2=R^3=H)	44.17 ± 13.61	67.66 ± 3.16	1.53	−	−	−	−	−
27 (R^1=I, R^2=R^3=H)	49.76 ± 14.25	50.99 ± 8.88	1.02	−	−	−	−	−
28 (R^1=R^2=H, R^3=NO2)	44.15 ± 5.38	210.34 ± 15.34	4.76	−	−	−	−	−
29 (R^1=R^3=H, R^2=NO2)	79.86 ± 15.40	205.76 ± 7.25	2.58	−	−	−	−	−
30 (R^1=NO2, R^2=R^3=H)	72.49 ± 1.23	23.58 ± 2.84	0.33	−	−	−	−	−
31 (Ar = Naphthyl)	28.72 ± 4.61	>256	>8.91	33.65 ± 5.72	>256	>7.61	39.66 ± 9.91	>6.45
R^1=R^2= R^3=H
36 R^4=OH, R^5=H	70.88 ± 10.96	46.29 ± 0.15	0.65	−	−	−	−	−
37 R^4=OMe R^5=H	39.79 ± 6,43	>256	>6.43	85.10 ± 17.15	>256	>3.01	−	−
38 R^4=R^5=OH	15.34 ± 2.22	45.19 ± 0.58	2.95	−	−	−	−	−
R^1=Me, R^2=R^3=H
39 R^4=OH, R^5=H	39.58 ± 7.08	60.99 ± 3.72	1.54	−	−	−	−	−
40 R^4=OMe R^5=H	>256	>256	ND^c	−	−	−	−	−
41 R^4=R^5=OH	118.61 ± 7.68	20.02 ± 1.87	0.17	−	−	−	−	−
R^1=OMe, R^2=R^3=H
42 R^4=OH, R^5=H	49.19 ± 9.97	43.31 ± 16.61	0.88	−	−	−	−	−
43 R^4=OMe R^5=H	26.75 ± 2.68	>256	>9.57	55.57 ± 16.30	>256	>4.61	39.04 ± 14.33	>6.56
R^1=F, R^2=R^3=H
44 R^4=OMe R^5=H	>256	>256	ND	−	−	−	−	−
45 R^4=R^5=OH	97.38 ± 5.33	30.47 ± 3.93	0.31	−	−	−	−	−
R^1=Cl, R^2=R^3=H
46 R^4=OMe R^5=H	30.53 ± 4.10	49.72 ± 3.76	1.63	−	−	−	−	−
R^1=Br, R^2=R^3=H
47 R^4=OH, R^5=H	42.79 ± 12.01	66.96 ± 5.43	1.56	−	−	−	−	−
48 R^4=OMe R^5=H	>256	>256	ND	−	−	−	−	−
49 R^4=R^5=OH	104.5 ± 15.71	16.71 ± 0.70	0.16	−	−	−	−	−
R^1=I, R^2=R^3=H
50 R^4=OH, R^5=H	22.80 ± 1.61	41.44 ± 8.36	1.82	−	−	−	−	−
51 R^4=OMe R^5=H	>256	>256	ND^c	−	−	−	−	−
52 R^4=R^5=OH	69.37 ± 4.73	20.82 ± 7.92	0.30	−	−	−	−	−
R^1=R^2=HR^3=NO2
53 R^4=OH, R^5=H	21.77 ± 2.98	34.89 ± 8.65	1.60	−	−	−	−	−
54 R^4=OMe R^5=H	210.40 ± 14.54	>256	>1.22	−	−	−	−	−
55 R^4=R^5=OH	41.99 ± 9.06	21.40 ± 4.12	0.51	−	−	−	−	−
R^1=R^3=HR^2=NO2
56 R^4=OH, R^5=H	36.85 ± 3.84	28.81 ± 3.25	0.78	−	−	−	−	−
57 R^4=OMe R^5=H	22.96 ± 6.33	>256	>11.15	>256	>256	ND	22.27 ± 4.20	>11.49
58 R^4=R^5=OH	33.79 ± 7.59	11.98 ± 1.42	0.35	−	−	−	−	−
R^1=NO2 R^2=R^3=H
59 R^4=OH, R^5=H	76.37 ± 9.91	29.44 ± 2.52	0.39	−	−	−	−	−
60 R^4=OMe R^5=H	>256	>256	ND	−	−	−	−	−
61 R^4=R^5=OH	110.56 ± 14.83	5.37 ± 0.30	0.05	−	−	−	−	−
62 R^4=NO2 R^5=H	>256	53.50 ± 4.82	<0.21	−	−	−	−	−
Ar = Naphthyl
63 R^4=OH R^5=H	53.65 ± 11.28	31.14 ± 9.21	0.58	−	−	−	−	−
64 R^4=OMe R^5=H	>256	>256	ND	−	−	−	−	−
65 R^4=R^5=OH	70.23 ± 6.99	28.79 ± 7.77	0.41	−	−	−	−	−
Benznidazole	25.31 ± 1.63	>256	>10.11	22.73 ± 1.82	>256	>11.26	0.47 ± 0.09	>544.68

^aResults are expressed as the mean ± SD of three independent experiments (n = 3).

^bSI CL-B5 epi = CC₅₀ L929/IC₅₀ CL lacZ epimastigotes, SI Y epi = CC₅₀ J774/IC₅₀ Y epimastigotes and SI CL-B5 ama = CC₅₀ L929/IC₅₀ CL lacZ amastigotes.

^cND: not determined.

Table 2. In vitro activity against Trichomonas vaginalis (IC₅₀), unspecific cytotoxicity of the most promising molecules against Vero cells (CC₅₀) and selectivity indexes (SI).

Compound	IC50 (µM)^a	CC50 (µM)	SI^b
23 (R^1=OMe, R^2=R^3=H)	255.70 [205.26–348.10]	–	–
24 (R^1=F, R^2=R^3=H)	200.49 [134.86–366.51]	–	–
25 (R^1=Cl, R^2=R^3=H)	49.19 [30.46–77.32]	>300	>6.10
27 (R^1=I, R^2=R^3=H)	75.69 [57.77–102.71]	–	–
28 (R^1=R^2=H, R^3=NO2)	>300	–	–
29 (R^1=R^3=H, R^2=NO2)	19.14 [14.92–23.52]	>300	>15.67
30 (R^1=NO2, R^2=R^3=H)	105.92 [63.13–236.25]	–	–
31 (Ar = Naphthyl)	30.20 [11.76–55.08]	>300	>9.93
R^1=R^2= R^3=H
36 R^4=OH, R^5=H	74.01 [60.18–92.68]	–	–
37 R^4=OMe R^5=H	167.29 [116.44–283.25]	–	–
38 R^4=R^5=OH	88.59 [65.64–125.65]	–	–
R^1=Me, R^2=R^3=H
39 R^4=OH, R^5=H	66.10 [43.85–103.72]	–	–
40 R^4=OMe R^5=H	225.96 [118.97–1084.50]	–	–
41 R^4=R^5=OH	80.61 [69.32–94.63]	–	–
R^1=OMe, R^2=R^3=H
42 R^4=OH, R^5=H	64.79 [55.04–76.69]	–	–
43 R^4=OMe R^5=H	257.50 [141.94–834.94]	–	–
R^1=F, R^2=R^3=H
44 R^4=OMe R^5=H	>300	–	–
45 R^4=R^5=OH	226.35 [192.65–275.96]	–	–
R^1=Cl, R^2=R^3=H
46 R^4=OMe R^5=H	32.27 [21.71–47.99]	>300	>9.30
R^1=Br, R^2=R^3=H
47 R^4=OH, R^5=H	52.36 [35.6–77.09]	–	–
48 R^4=OMe R^5=H	55.14 [47.61–63.92]	–	–
49 R^4=R^5=OH	16.39 [0.08–28.72]	>300	>18.30
R^1=I, R^2=R^3=H
50 R^4=OH, R^5=H	42.25 [36.30–48.52]	>300	>7.10
51 R^4=OMe R^5=H	14.85 [5.94–24.24]	>300	>20.20
52 R^4=R^5=OH	24.89 [11.95–41.25]	>300	>12.05
R^1=R^2=HR^3=NO2
53 R^4=OH, R^5=H	92.80 [81.78–103.30]	–	–
54 R^4=OMe, R^5=H	34.20 [29.47–39.39]	>300	>8.77
55 R^4=R^5=OH	132.56 [120.93–146.15]	–	–
R^1=R^3=HR^2=NO2
56 R^4=OH, R^5=H	24.28 [12.49–38.45]	168.93 [127.03–239–12]	7.00
57 R^4=OMe R^5=H	51.91 [31.66–85.57]	–	–
58 R^4=R^5=OH	73.41 [50.52–110.14]	–	–
R^1=NO2 R^2=R^3=H
59 R^4=OH, R^5=H	35.95 [29.98–42.63]	254.15 [170.16–725.83]	7.07
60 R^4=OMe R^5=H	155.17 [93.43–395.10]	–	–
61 R^4=R^5=OH	127.98 [77.11–294.93]	–	–
62 R^4=NO2 R^5=H	151.81 [112.95–209.64]	–	–
Ar = Naphthyl
63 R^4=OH R^5=H	14.89 [11.51–18.30]	274.75 [193.19–562.70]	18.45
64 R^4=OMe R^5=H	30.46 [17.60–46.35]	>300	>9.85
65 R^4=R^5=OH	20.14 [16.37–24.03]	174.81 [110.58–371.96]	>8.68
Metronidazole	2.68 [2.37–3.03]	>300	>111

IC₅₀ and CC₅₀ were calculated with growth inhibition values showing a standard deviation of less than 10%.

–: Not evaluated against Vero cells owing to the low trichomonacidal activity.

^aResults in brackets refer to 95% confidence interval.

^bSelectivity indexes SI = CC₅₀ Vero cells/IC₅₀ T. vaginalis.

Figure 2. Plots of fluorescence units at 535 nm after addition of JC-1. MTZ (metronidazole), CCCP (m-chlorocarbonylcyanide phenylhydrazone) and CC (culture control). Data indicate mean ± SD of three independent experiments (n = 3). Data that are significantly different from control experiment are marked with an asterisk (*) (ρ < 0.05).

Figure 3. Fluorescence emitted by JC-1 in hydrogenosome. A. Control. B. Positive control (treatment with the uncoupler agent CCCP). C. Treatment with MTZ. D. Treatment with 51. E. Treatment with 63.

Figure 4. Scanning electron microscopy images of T. vaginalis cultures. A. Control. B. Treatment with compound 51. C. Treatment with compound 63.