Synthesis and biological evaluation of 2-amino-5-sulfanyl-1,3,4-thiadiazole derivatives as antidepressant, anxiolytics and anticonvulsant agents

Article abstract of DOI:10.1007/s00044-010-9308-3

A new series of 2-amino-5-sulfanyl-1,3,4-thiadiazole derivatives has been synthesized. The newly synthesized compounds were characterized by analytical and spectral methods. Compounds were screened for central nervous system activity. Compounds 1, 5, 7, 1

Full text of DOI:10.1007/s00044-010-9308-3

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2011) 20:245–253
DOI 10.1007/s00044-010-9308-3
ORIGINAL RESEARCH
Synthesis and biological evaluation of 2-amino-5-sulfanyl-1,3,
4-thiadiazole derivatives as antidepressant, anxiolytics
and anticonvulsant agents
•
Rajesh Sharma Ganesh Prasad Misra
•
•
Jitendra Sainy Subhash Chandra Chaturvedi
Received: 15 July 2009 / Accepted: 13 January 2010 / Published online: 10 February 2010
Ó Springer Science+Business Media, LLC 2010
Abstract A new series of 2-amino-5-sulfanyl-1,3,4-thia-
diazole derivatives has been synthesized. The newly syn-
thesized compounds were characterized by analytical and
spectral methods. Compounds were screened for central
nervous system activity. Compounds 1, 5, 7, 10, 14
exhibited significant antidepressant, anxiolytic and anti-
convulsant activity in comparison to the reference drugs.
synthesize some new derivatives to evaluate for antide-
pressant, anxiolytic and anticonvulsant activity. The syn-
thetic pathway is given in Scheme 1.
Materials and methods
Chemistry
Keywords 2-Amino-5-sulfanyl-1,3,4-thiadiazole Á
Antidepressant Á Anxiolytic and anticonvulsant activity
Melting points were determined in an open capillary tube
and uncorrected. Purity of the compounds was checked on
pre-coated silica gel G plates (0.2 mm thickness, Merck,
India) using iodine vapor as visualizing agent. Infrared
spectra were recorded on a Perkin Elmer Paragon 1000 IR
Introduction
1
Substituted thiadiazole derivatives have been found to
show diverse pharmacological activities such as analgesic
(Schenone et al., 2006), antidepressant and anxiolytic
(Clerici and Pocar, 2001), anticonvulsant (Stillings et al.,
1986; Chapleo et al., 1986), anti-inflammatory (Mullican
et al., 1993), antimicrobial (Servi et al., 2005), antituber-
cular (Oruc¸ et al., 2004), antitumor (Matysiak, 2006) and
antiviral (Jones et al., 1965) activity. A series of 2-amino-
5-sulfanyl-1,3,4-thiadiazoles originally been synthesized
and evaluated for antidepressant and anxiolytic activity by
Clerici and Pocar (2001). Due to their effect on central
nervous system (CNS) it was considered worthwhile to
spectrometer (USA) and H-NMR spectra were obtained
on a Bruker DRX-300 MHz FT NMR spectrometer (USA)
in CDCl3. All chemical shifts were reported as d (ppm)
values. Mass spectra were recorded on a Jeol SX-102 mass
spectrometer (Japan). Elemental analyses were performed
on an Elemental Vario EL II/Carlo N 1108 (Italy) and
satisfactory results 0.4% of calculated values (C, H, N)
were obtained. All the reagents used in the present work
were of synthetic grade (Aldrich, Germany, Lancaster,
UK). The various substitution was made on sulfanyl and
amino group of 2-amino-5-sulfanyl-1,3,4-thiadiazole
nucleus. The various substituents are presented in Table 1.
R. Sharma (&) Á G. P. Misra Á J. Sainy
School of Pharmacy, Devi Ahilya Vishwavidyalaya,
Thakshyasila Campus, Khandwa Road, Indore, Madhya Pradesh
452 001, India
Synthesis of compounds
Synthesis of 4-[5-chlorophenylamino)-1,3,4-
e-mail: rbsm73@yahoo.co.in
thiadiazole-2-yl-sulphanyl]-benzenesulphonamide (1)
S. C. Chaturvedi
College of Pharmacy, IPS Academy, A.B. Road, Rau, Indore,
Madhya Pradesh 452 001, India
2-Amino-5-sulfanyl-1,3,4-thiadiazole (I) (0.01 mol, 1.31 g)
was suspended in a minimum quantity of water and a
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N
N
N
N
N
N
0- 5°C
Ar1Cl
85%KOH, 0°C
ArCl
HN
S
H2N
S
S
S
H2N
S
SH
(I)
R1
R
R
(1- 15)
Scheme 1 General synthetic pathway for compounds (1–15). ArCl: 4-
chlorobenzene sulfonamide (1, 3, 5, 7, 9, 11, 14, 15) and 4-chlorobenzene
sulfonylchloride (2, 4, 6, 8, 10, 12, 13). Ar1Cl: 1,4-disubstitutedben-
zene[1,4-dichlorobenzene (1,2), 1-bromo-4-chlorobenzene (3, 4), 1-
chloro-4-fluorobenzene (5, 6), 1-chloro-4-methylbenzene (7, 8), 1-
chloro-4-trifluoromethylbenzene (9, 10), 1-chloro-4-trichloromethylben-
zene (11, 12), 4-chlorobenzene sulfonylchloride (13, 14), 4-chloroben-
zene sulfonamide (15)
was added under vigorous stirring. The reaction mixture
was checked by thin layer chromatography.
Table 1 Substituents on 2-amino-5-sulfanyl-1,3,4-thiadiazole nucleus
N
N
The solution was neutralized upon completion of the
reaction. The precipitate of 4-[5-amino-(1,3,4)thiadiazole-
2-yl-sulphanyl]benzene sulphonamide formed slowly. It
was filtered, washed with distilled water and crystallized
using ether as a solvent. The purity of the synthesized
intermediate was ascertained by thin layer chromatography
using a methanol and xylene mixture (4:6, V/V). The
intermediate (0.01 mol; 2.88 g) was dissolved in ether and
1,4-dichlorobenzene (0.01 mol, 1.48 g) was added under
stirring while maintaining the temperature between 0 and
5°C. After 30 min, water was added and a precipitate was
formed. Filtration of the compound and recrystallization
from ether yielded compound 1. Yield 75%, m.p:
141–142°C. Spectroscopic analysis: IR (cm-1, KBr) 3334
(NH asym.), 3285 (NH sec.), 3241 (NH sym.), 3100 (C–H,
sp2),1637 (C=C/C=N),1606, 1572, 1475(C=C ring
str.),1331 (S (=O2) asym.),1165 (S (=O2) sym.), 627 (C–S),
S
S
HN
R
R1
Compounds
R
R1
1
–SO2NH2
–SO2Cl
–Cl
2
–Cl
3
–SO2NH2
–SO2Cl
–Br
4
–Br
5
–SO2NH2
–SO2Cl
–F
1
540 (C–Cl), H NMR (d ppm): 2.51 (s, 2H, NH2),4.40 (s,
6
–F
NH),7.47 (s, 4H, Ar-H), 7.64–7.67 (d, 2H, Ar-Ha),
7.82–7.85 (d, 2H, Ar-Hb), MS (m/z): 398 (M?, 15), 400
(M? ?2,5), 274 (100),156 (55), 111 (25). Anal. calcd. for
C14H11ClN4O2S3: C, H, N in %: Calc: 42.15, 2.78, 14.04.
Obs: 42.05, 2.68, 14.00.
7
–SO2NH2
–SO2Cl
–CH3
–CH3
–CF3
–CF3
–CCl3
–CCl3
–SO2Cl
–SO2Cl
–SO2NH2
8
9
–SO2NH2
–SO2Cl
10
11
12
13
14
15
–SO2NH2
–SO2Cl
Compounds 2–15 were synthesized using procedure
described for compound 1.
–SO2Cl
–SO2NH2
–SO2NH2
4-[5-(4-Chloro-phenylamino)-[1,3,4]thiadiazol-2-
ylsulfanyl]-benzenesulfonylchloride (2)
Yield: 78%; mp: 136–37°C. Spectroscopic analysis: IR
(cm-1, KBr): 3285 (NH asym.), 3240 (NH sec.), 3118 (NH
sym.), 3096 (C–H, sp2), 1656 (C=C/C=N), 1634, 1572,
1435 (C=C ring str.), 1331 (S (=O2) asym.), 1176 (S (=O2)
sufficient quantity of 85% KOH solution was added under
stirring at room temperature. After a few minutes (5–10),
the solution was brought to 0°C in an ice bath and
4-chlorobenzene sulfonamide (ArCl) (0.01 mol, 1.92 g)
1
sym.), 626 (C–S), 560 (C–Cl). H NMR (d ppm): 3.42 (s,
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Med Chem Res (2011) 20:245–253
247
1
NH), 7.48 (Cl, 2H, Ar-Ha), 7.65 (Cl, 2H, Ar-Hb), 7.75 (Cl,
2H, Ar-Hc), 7.85 (Cl, 2H, Ar-Hd). MS (m/z): 418 (M?, 5),
420 (M? ?2, 10), 422 (M? ?4,5), 274 (100), 111 (18).
Anal. calcd. for C14H11ClN4O2: C, H, N in %: Calc: 40.19,
2.17, 10.04, Obs: 40.19, 2.11, 10.01.
910, 840, 720 (sub. phenyl), 620 (C-S). H NMR (d ppm):
4.0 (s, NH), 6.44 (d, 2H, Ar-Ha), 6.72 (d, 2H, Ar-Hb), 7.41
(d, 2H, Ar-Hc), 7.78 (d, 2H, Ar-Hd). MS (m/z): 401 (M?,
87), 403 (M? ?2, 16), 405 (M? ?4, 8). Anal. calcd. for
C14H9ClFN3O2S3: C, H, N in %: Calc: 41.84, 2.26, 10.46,
Obs: 41.75, 2.19, 10.42.
4-[5-(4-Bromo-phenylamino)-[1,3,4]thiadiazol-2-
ylsulfanyl]-benzenesulfonamide (3)
4-(5-p-Tolylamino-[1,3,4]thiadiazol-2-ylsulfanyl)-
benzenesulfonamide (7)
Yield: 67%. m.p: 125–126°C. Spectroscopic analysis: IR
(cm-1, KBr): 3500 (NH asym.), 3390 (NH sym.), 3280
(NH sec.), 3050 (C–H, sp2), 1640 (C=C/C=N), 1600, 1500,
1395 (C=C ring str.), 1300 (S (=O2) asym.), 1120 (S (=O2)
sym.), 680 (C–S), 560 (C–Br).1H NMR (d ppm): 2.01 (s,
2H, NH2), 3.41 (s, NH), 7.48 (s, 4H, Ar-H), 7.65–7.68 (Cl,
2H, Ar-Ha), 7.83–7.86 (Cl, 2H, Ar-Hb). MS (m/z): 443
(M?, 24), 445 (M? ?2, 8), 274 (100). Anal. calcd. for
C14H11BrN4O2S3: C, H, N in %: Calc: 37.93, 2.50,12.64,
Obs: 37.53, 2.42, 12.34.
Yield: 70%. m.p: 244–245°C. Spectroscopic analysis: IR
(cm-1, KBr): 3333 (NH asym.), 3286 (NH sec.), 3240 (NH
sym.), 3090 (C–H, sp2), 2850 (C–H, sp3), 1634 (C=C/
C=N), 1572, 1506, 1435 (C=C ring str.), 1329 (S (=O2)
asym.), 1167 (S (=O2) sym.), 627 (C-S). 1H NMR (d ppm):
2.35 (s, 3H, CH3), 3.43 (s, NH), 7.48 (s, H H, Ar-H),
7.65–7.69 (Cl, 2H, Ar-Ha), 7.83–7.86 (Cl, 2H, Ar-Hb). MS
(m/z): 378 (M?, 25), 274 (100), 91 (45). Anal. calcd. for
C15H14N4O2S3: C, H, N in %: Calc: 47.60, 3.73, 14.80,
Obs: 47.44, 3.66, 14.66.
4-[5-(4-Bromo-phenylamino)-[1,3,4]thiadiazol-2-
ylsulfanyl]-benzenesulfonylchloride (4)
4-(5-p-Tolylamino-[1,3,4]thiadiazol-2-ylsulfanyl)-
benzenesulfonylchloride (8)
Yield: 69%. m.p: 192–93°C. Spectroscopic analysis: IR
(cm-1, KBr): 3350 (NH asym.), 3210 (NH sec.), 3185 (NH
sym.), 3050 (C–H, sp2), 1590 (C=C/C=N), 1600, 1500,
Yield: 68%. m.p: 111–112°C. Spectroscopic analysis: IR
(cm-1, KBr): 3270 (N–H, sec.), 3070 (C–H, sp2), 2850 (C–
H, sp3), 1630 (C=C/C=N), 1595, 1500, 1400 (C=C ring
str.), 1350 (S (=O2) asym.), 1140 (S (=O2) sym.), 610 (C-
S). 1H NMR (d ppm): 2.35 (s, 3H, CH3), 3.43 (s, NH), 6.34
(d, 2H, Ar-Ha), 6.81 (d, 2H, Ar-Hb), 7.41 (d, 2H, Ar-Hc),
7.78 (d, 2H, Ar-Hd). MS (m/z): 397 (M?, 18), 399 (M? ?2,
6), 91(40). Anal. calcd. for C15H12ClN3O2S3: C, H, N in %:
Calc: 45.27, 3.04, 10.56. Obs: 45.11, 2.99, 10.49.
1
1495 (C=C ring str.), 670 (C–S), 550 (C–Br). H NMR (d
ppm): 3.42 (s, NH), 6.85 (Cl, 2H, Ar-Ha), 7.18 (Cl, 2H, Ar-
Hb), 7.41 (Cl, 2H, Ar-Hc), 7.78 (Cl, 2H, Ar-Hd). MS (m/z):
462 (M?, 10), 464 (M? ?2, 20), 466 (M? ?4, 70). Anal.
calcd. for C14H9BrClN3O2S3: C, H, N in %: Calc: 36.33,
1.96, 9.08, Obs: 36.23, 1.89, 9.01.
4-[5-(4-Fluoro-phenylamino)-[1,3,4]thiadiazol-2-
ylsulfanyl]-benzenesulfonamide (5)
4-[5-(4-Trifluoromethyl-phenylamino)-
[1,3,4]thiadiazol-2-ylsulfanyl]-benzenesulfonamide (9)
Yield: 80%. m.p: 101–102°C. Spectroscopic analysis: IR
(cm-1, KBr): 3289 (NH asym.), 3241 (NH sec.), 3150 (NH
sym.), 3100 (C–H, sp2), 1656 (C=C/C=N), 1572, 1506,
1475 (C=C ring str.), 1386 (S (=O2) asym.), 1176 (S (=O2)
Yield: 65%. m.p: 134–36°C. Spectroscopic analysis: IR
(cm-1, KBr): 3333 (NH asym.), 3241 (NH sec.), 3151 (NH
sym.), 3070 (C–H, sp2), 1633 (C=C/C=N), 1572, 1506,
1
1
sym.), 1022 (C-F), 626 (C-S). H NMR (d ppm): 2.50 (S,
1498 (C=C ring str.), 1151 (C–F), 627 (C–S). H NMR (d
2H, NH2), 3.49 (S, NH), 7.48 (S, 4H, Ar-H), 7.65–7.68 (Cl,
2H, Ar-Ha), 7.82–7.85 (Cl, 2H, Ar-Hb). MS (m/z): 382
(M?, 27), 384 (M? ?2, 9), 274 (100). Anal. calcd. for
C14H11FN4O2S3: C, H, N in %: Calc: 43.97, 2.90, 14.65,
Obs: 43.57, 2.70, 14.55.
ppm): 2.51 (s, 2H, NH2), 3.41 (s, NH), 6.39 (d, 2H, Ar-Ha),
7.20 (d, 2H, Ar-Hb), 7.46 (d, 2H, Ar-Hc), 7.77 (d, 2H, Ar-
Hd). MS (m/z): 432 (M?, 4), 434 (M? ?2, 12), 436 (M? ?4,
12), 430 (M, ?6, 4). Anal. calcd. for C15H11F3N4O2S3: C,
H, N in %: Calc: 41.66, 2.56, 12.96. Obs: 41.64, 2.35, 12.77.
4-[5-(4-Fluoro-phenylamino)-[1,3,4]thiadiazol-2-
4-[5-(4-Trifluoromethyl-phenylamino)-[1,3,4]
ylsulfanyl]-benzenesulfonylchloride (6)
thiadiazol-2-ylsulfanyl]-benzenesulfonylchloride (10)
Yield: 72%. m.p: 220–222°C. Spectroscopic analysis: IR
(cm-1, KBr): 3340 (N–H, asym.), 3215 (N–H, sym.), 1660
(C=C/C=N), 1600, 1490, 1405 (C=C ring str.), 980 (C-F),
Yield: 78%, m.p: 116–18°C, IR (cm-1, KBr): 3245 (N–H,
sec.), 3075 (C–H, sp2), 1600, 1500, 1400 (C=C ring str.),
1640 (C=C/C=N), 1336 (S (=O2) asym.), 1152 (S (=O2)
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sym.), 1090 (C–F). 1H NMR (d ppm): 4.0 (s, NH), 6.39 (d,
2H, Ar-Ha), 7.20 (d, 2H, Ar-Hb), 7.41 (d, 2H, Ar-Hc), 7.78
(d, 2H, Ar-Hd). MS (m/z): 452 (M?, 8). Anal. calcd. for
C15H9ClF3N3O2S3: C, H, N in %: Calc: 39.87, 2.01, 9.30,
Obs: 39.68, 1.99, 9.22.
Ar-Hc), 7.68 (d, 2H, Ar-Hb), 7.83 (d, 2H, Ar-Hd). MS (m/z):
463 (M?, 24) 465 (M? ?2, 8), 274 (100), 175 (40). Anal.
calcd. for C14H11ClN4O4S4: C, H, N in %: Calc: 36.32,
2.39, 2.10. Obs: 36.28, 2.38, 12.06.
4-[5-(4-Sulfamoyl-phenylsulfanyl)-[1,3,4]thiadiazol-2-
4-[5-(4-Trichloromethyl-phenylamino)-[1,3,4]thiadiazol
ylamino]-benzenesulfonamide (15)
-2-ylsulfanyl]-benzenesulfonamide (11)
Yield: 60%. m.p: 133–134°C. Spectroscopic analysis: IR
(cm-1, KBr): 3310 (–NH, asymmetric), 3250 (N–H, sym.),
1640 (C=C/C=N), 1595, 1500, 1390 (C=C ring str.), 1345
(S (=O2) asym.), 1150 (S (=O2) sym.), 810,790,740 (sub.
Yield: 58%. m.p: 137–38°C. Spectroscopic analysis: IR
(cm-1, KBr): 3334 (NH asym.), 3240 (NH sec.), 3151 (NH
sym.), 3050 (C–H, sp2), 1651 (C=C/C=N), 1614, 1505,
1409 (C=C ring str.), 1328 (S (=O2) asym.), 1176 (S (=O2)
sym.), 1014 (C–Cl), 627 (C–S). 1H NMR (d ppm): 2.51 (s,
2H, NH2), 3.49 (s, NH), 7.55–7.58 (d, 2H, Ar-Ha),
7.64–7.67 (d, 2H, Ar-Hb), 7.82–7.85 (d, 2H, Ar-Hc),
7.93–7.96 (d, 2H, Ar-Hd). MS (m/z): 482 (M?, 8). Anal.
calcd. for C15H11Cl3N4O2S3: C, H, N in %: Calc: 37.39,
2.30, 11.63. Obs: 37.28, 2.19, 11.54.
1
phenyl), 590 (C–S). H NMR (d ppm): 2.52 (s, 2H, NH2),
3.46 (s, NH), 7.36–7.39 (d, 2H, Ar-Ha), 7.50–7.59 (d, 2H,
Ar-Hc), 7.64–7.67 (d, 2H, Ar-Hb), 7.85–7.88 (d, 2H, Ar-
Hd). MS (m/z): 443 (M?, 25), 274 (100), 156 (45). Anal.
calcd. for C14H13N5O4S4: C, H, N in %: Calc: 37.91, 2.95,
15.79. Obs: 37.88, 2.91, 15.62.
4-[5-(4-Trichloromethyl-phenylamino)-[1,3,4]thiadiazol-
Biological activity
2-ylsulfanyl]-benzenesulfonylchloride (12)
Antidepressant activity was determined by the tail sus-
pension test in Steru et al. (1985) and despair swim test in
mice (Porsolt et al., 1977), anxiolytic activity was deter-
mined by elevated plus maze test (Moser, 1989; Rabbani
et al., 2004) and light and dark box model (Crawley and
Goodwin, 1980) by using balb/cj mice and Swiss albino
mice respectively. Balb/cj mice and Swiss albino mice
(20–25 g of body mass) of both sexes were divided into
different groups (control, test and standard) containing six
animals each. The animals were housed in standard poly-
propylene cages under standard laboratory conditions
(12:12 hour light/dark cycle at 25 3°C).They had free
access to standard commercial diet and water. The ethical
guidelines for the investigations of animals used in
experiments were followed in all tests.
Yield: 71%. m.p: 125–127°C. Spectroscopic analysis: IR
(cm-1, KBr): 3250 (N–H, sec.), 3040 (C–H, sp2), 1650
(C=C/C=N), 590, 1505, 1400 (C=C ring str.), 1333 (S
1
(=O2) asym.), 1150 (S (=O2) sym.), 550 (C–Cl). H NMR
(d ppm): 3.49 (s, NH), 6.39 (d, 2H, Ar-Ha) 7.56 (d, 2H, Ar-
Hb), 7.41 (d, 2H, Ar-Hc), 7.75 (d, 2H, Ar-Hd). MS (m/z):
501 (M?, 12). Anal. calcd. for C15H9Cl4N3O2S3: C, H, N in
%: Calc: 35.94, 1.81, 8.38. Obs: 35.78, 1.75, 8.16.
4-[5-(4-Chlorosulfonyl-phenylsulfanyl)-[1,3,4]thiadiazol-
2-ylamino]-benzenesulfonylchloride (13)
Yield: 82%. m.p: 152–153°C. Spectroscopic analysis: IR
(cm-1, KBr): 3285 (N–H, sec.), 3070 (C–H, sp2), 1640
(C=C/C=N), 1610, 1595, 1405 (C=C ring str.), 1340 (S
(=O2) asym.), 1145 (S (=O2) sym.). 1H NMR (d ppm): 3.53
(s, NH), 6.69 (d, 2H, Ar-Ha), 7.69 (d, 2H, Ar-Hb), 7.41 (d,
2H, Ar-Hc), 7.75 (d, 2H, Ar-Hd). MS (m/z): 482 (M?, 5).
Anal. calcd. for C14H9Cl2N3O4S4: C, H, N in %: Calc:
34.86,1.88,8.71. Obs: 34.71, 1.76, 8.52.
Tail suspension test
In this study, the animals were administered 30 mg kg-1
(body mass) dose of the test drug and 15 mg kg-1 (body
mass) dose of standard drug fluoxetine hydrochloride. The
test and standard compounds were suspended in 10%
tween-20 suspension and administered intraperitoneally
30 min prior to testing. The control group animals, how-
ever, received the same volume of vehicle (10% tween-20
suspension). Test mice were suspended on the edge of a
shelf 58 cm above a table top by adhesive tape placed
approximately 1 cm from the tip of tail. The duration of
immobility is reported for a period of 5 min and this time
were divided into 20 phases and each phase consist of 15 s
mice were considered immobile when they hang passively
4-[5-(4-Sulfamoyl-phenylsulfanyl)-[1,3,4]thiadiazol-2-
ylamino]-benzenesulfonylchloride (14)
Yield: 68%. m.p: 105–106°C. Spectroscopic analysis: IR
(cm-1, KBr): 3271 (N–H, asym.), 3185 (N–H, sym.), 3087
(C–H, sp2), 1638 (C=C/C=N), 1539, 1504, 1400 (C=C ring
str.), 1336 (S (=O2) asym.), 1139 (S (=O2) sym.), 846, 824,
1
774 (sub. phenyl), 610 (C–S). H NMR (d ppm): 2.51 (s,
2H, NH2), 3.53 (s, NH), 7.48 (d, 2H, Ar-Ha), 7.65 (d, 2H,
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Med Chem Res (2011) 20:245–253
249
and completely motionless for at least 10–12 s out of 15 s.
The results are reported in Table 2 and were analyzed for
statistical significance using Students t-test and significant
was set at P \ 0.05.
Table 3 Antidepressant activity of 2-amino-5-sulphanyl-1,3,4-thia-
diazole derivatives: despair swim test
Compounds
Duration of
immobility
(mean SEM)
Percentage decrease
in immobility compared
to negative control
Despair swim test
Positive control
100.01 0.01
98.86 0.02
69.98 0.01*
75.22 0.03
71.93 0.03
68.52 0.01
48.95 0.01**
76.32 0.02
47.90 0.03**
69.99 0.02
71.25 0.03**
45.96 0.01*
74.14 0.02*
68.96 0.01*
73.24 0.02
48.99 0.01**
73.92 0.02
40.93 0.01**
609.80
–
Negative control
–
The development of immobility when mice are placed in
an inescapable cylinder filled with water reflects the ces-
sation of persistent escape directed behavior. The apparatus
consisted of a clear plexi glass cylinder (25 9 12 9
25 cm3) filled to 15 cm depth with water (24 1°C). Two
session were conducted: an initial 15-min training session
(pretest session) followed 24 h later by a 6-min test session
following the training session mice were removed from the
cylinder, towel dried and placed under a lamp for 5 min
then returned to the home cage for testing the next day. A
mouse was considered to be immobile when it remains
floating in the water without struggling, making only
minimum movements of its limbs necessary to keep its
head above water. The total duration of immobility was
recorded during the next 4-min of a total 6-min test. In this
study, the animals were administered 30 mg kg-1 (body
mass) dose of the test drug and 15 mg kg-1 (body mass)
dose of standard drug fluoxetine hydrochloride. The test
and standard compounds were suspended in 10% tween-20
suspension and administered intraperitoneally 30 min prior
to testing. The control group animals, however, received
the same volume of vehicle (10% tween-20). The results
1
29.21
23.91
27.24
30.68
50.48
22.79
51.54
29.20
27.92
53.51
25.00
30.24
25.91
50.44
25.22
58.59
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Fluoxetine HCl
One-way ANOVA f
df
17,90
P
\0.0001
n = 6 in each group
** p \ 0.0001, * p \ 0.001 compared against control group
Table 2 Antidepressant
activity of 2-amino-5-
sulphanyl-1,3,4-thiadiazole
derivatives: tail suspension test
Compounds
Number of mobile
phase in pretreatment
period (mean SEM)
Number of mobile phase
in post-treatment period
(mean SEM)
% increase in mobile
phase as compare
to pretreatment
Positive control
12.30 1.20
11.50 0.20
10.50 1.38
11.67 0.80
11.67 0.98
10.50 0.67
9.50 0.42
10.83 0.60
10.66 0.88
13.16 0.87
8.50 0.76
8.33 0.33
11.16 0.60
10.50 0.50
13.17 1.04
10.67 1.28
16.50 0.42
7.00 0.73
13.00 0.50
14.50 0.80
14.00 1.57
13.50 0.84
13.50 1.17
12.66 0.61*
13.33 0.66**
13.00 0.85*
15.16 1.00*
15.16 0.67
11.16 0.90*
12.16 0.30**
13.00 0.77*
12.50 0.67*
14.50 1.08
15.00 1.43*
18.16 0.47*
10.50 0.99*
5.69
26.08
33.33
15.68
15.68
20.57
40.31
21.51
42.21
15.19
31.29
45.97
16.39
19.16
10.09
40.58
10.06
50.00
Negative control
1
2
3
4
5
6
7
8
9
10
11
12
13
14
n = 6 in each group
15
** p \ 0.05, * p \ 0.001
compared against control group
Fluoxetine HCl
123

250
Med Chem Res (2011) 20:245–253
Light and dark box model
are reported in Table 3 and were analyzed for statistical
significance using one-way ANOVA followed by Dunnet’s
test and significant was set at P \ 0.05.
In this model each mouse was placed individually in the
centre of the white area and behavioral parameters were
recorded over a 5-min period. In this study, the animals
were administered 30 mg kg-1 (body mass) dose of the
test drug and 2 mg kg-1 (body mass) dose of standard drug
diazepam. The test and standard compounds were sus-
pended in 1% carboxymethyl cellulose and administered
intraperitoneally 30 min prior to testing. The control group
animals, however, received the same volume of vehicle
(1% carboxymethyl cellulose). Two behavioral parameters
were measured in the white area: the number of transition
between the two chambers (n) and time (seconds) spent in
the light chamber. The results are reported in Table 5 and
were analyzed for statistical significance using one-way
ANOVA followed by Dunnet’s test and significant was set
at P \ 0.05.
Elevated plus maze test
In elevated plus maze model each mouse was placed in the
central platform facing one open arm. The numbers of
entries into open and closed arms and the time spent in the
respective arms were recorded for a 5-min period. In this
study, the animals were administered 30 mg kg-1 (body
mass) dose of the test drug and 2 mg kg-1 (body mass)
dose of standard drug diazepam. The test and standard
compounds were suspended in 1% carboxymethyl cellulose
and administered intraperitoneally 30 min prior to testing.
The control group animals, however, received the same
volume of vehicle (1% carboxymethyl cellulose). The
percentage preference of animals to open arm, increases in
number of entries and time spent in the open arms were
calculated for each mouse. The results are reported in
Table 4 and were analyzed for statistical significance using
one-way ANOVA followed by Dunnet’s test and signifi-
cant was set at P \ 0.05.
Anticonvulsant activity were determined by Maximal-
electro-shock (MES)-induced convulsion (Woodbury and
Davenport, 1952) and Pentylenetetrazole-induced-clonic
convulsion (Ahmadiani et al., 2003; Ambawade et al.,
2002) using albino rats of Wistar strain (150–200 g of body
mass) of both sexes were divided into different groups
Table 4 Anxiolytic activity of
Compounds
% preference
to open arm
Open arm
2-amino-5-sulphanyl-1,3,4-
thiadiazole derivatives: elevated
plus maze test
No. of entries
(mean SEM)
Average time spent
(mean SEM)
Positive control
4.80
5.01
2.50 0.01
2.20 0.01
4.01 0.01**
2.23 0.02
3.01 0.02*
2.99 0.01*
4.00 0.02*
3.06 0.01
4.20 0.01*
2.21 0.02*
2.35 0.02*
4.80 0.01**
2.56 0.02*
2.54 0.01
3.09 0.01
4.06 0.02**
2.26 0.01
4.90 0.01**
650.9
12.25 0.02
14.00 0.01
45.51 0.02*
30.01 0.01
29.26 0.02
25.20 0.01
46.31 0.02**
25.26 0.01
45.69 0.01**
22.20 0.02
23.72 0.02**
47.92 0.01**
24.20 0.02
26.20 0.01
27.63 0.02
45.93 0.01**
26.64 0.01
60.01 0.02**
254.0
Negative control
1
16.35
9.75
2
3
8.01
4
9.25
5
18.01
10.54
18.25
7.58
6
7
8
9
8.92
10
18.92
7.85
11
12
8.75
13
7.90
14
17.20
6.65
15
Fluoxetine HCl
One-way ANOVA f
20.21
n = 6 in each group
df
17,90
17,90
** p \ 0.0001, * p \ 0.001
compared against control group
P
\0.0001
\0.0001
123

Med Chem Res (2011) 20:245–253
251
Table 6 and were analyzed for statistical significance using
one-way ANOVA followed by Dunnet’s test and signifi-
cant was set at P \ 0.05.
Table 5 Anxiolytic activity of 2-amino-5-sulphanyl-1,3,4-thiadia-
zole derivatives: light and dark box model
Compounds
Number of transition
between two chambers
(mean SEM)
Time spent in
the light chamber
(mean SEM)
Pentylenetetrazole-induced-clonic convulsion
Positive control
1.98 0.02
1.20 0.01
2.70 0.01**
1.66 0.02
1.98 0.02
2.01 0.01*
2.92 0.02**
1.99 0.02
2.88 0.02**
2.12 0.01
2.11 0.01
2.99 0.01**
2.13 0.01**
2.00 0.03
2.20 0.02*
2.85 0.03**
2.73 0.01*
3.10 0.01**
260.1
130.20 0.01
135.25 0.01
178.20 0.01**
151.50 0.01
162.30 0.03
159.30 0.01
185.90 0.03*
166.30 0.01
190.25 0.03*
169.25 0.03
151.26 0.03
192.00 0.02*
162.00 0.03
170.50 0.03
172.50 0.03
180.25 0.03**
133.20 0.03
196.25 0.03
255.2
Negative control
Pentylenetetrazol used as chemo-convulsant and dissolved
in normal saline. In this study, the animals were administered
30 mg kg-1 (body mass) dose of the test drug and
4 mg kg-1 (body mass) dose of standard drug diazepam. The
test and standard compounds were suspended in 1% car-
boxymethyl cellulose and administered intraperitoneally
30 min prior to intraperitoneal administration of pentylen-
etetrazole 80 mg kg-1 (body mass). The control group ani-
mals however received the same volume of vehicle (1%
carboxymethyl cellulose) and observed the onset of con-
vulsion. The results are reported in Table 7 and were ana-
lyzed for statistical significance using one-way ANOVA
followed by Dunnet’s test and significant was set at
P \ 0.05.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Diazepam
One-way ANOVA f
Table 6 Anticonvulsant activity of 2-amino-5-sulphanyl-1,3,4-thia-
diazole derivatives: maximal-electro-shock (MES)-induced convulsion
df
17,90
17,90
P
\0.0001
\0.0001
Compounds
Duration of tonic
hind limb extensor
(mean SEM)
% of animal
protected
n = 6 in each group
** p \ 0.0001 and * P \ 0.001 compared against the control group
Positive control
15.71 0.01
15.25 0.05
5.17 0.02**
7.55 0.05**
8.01 0.02
7.63 0.01*
4.50 0.01*
8.25 0.01
4.52 0.03**
8.01 0.01
7.37 0.05*
4.42 0.03
6.96 0.01*
7.01 0.01**
8.50 0.02
4.69 0.02**
8.25 0.01**
Absent
0
Negative control
0
(control, test and standard) containing six animals each.
The animals were housed in standard polypropylene cages
under standard laboratory conditions (12:12 hour light/dark
cycle at 25 3°C). They had free access to standard
commercial diet and water. The ethical guidelines for the
investigations of animals used in experiments were fol-
lowed in all tests.
1
50
2
16.66
33.33
0
3
4
5
66.66
0
6
7
50
8
16.66
33.33
66.66
16.66
16.66
0
Maximal-electro-shock (MES)-induced convulsion
9
10
In this test, the rats were subjected to 50 mA of alternating
current from a convulsiometer for 0.2 s through a pair of
electrodes attached to each ear. The duration of the tonic
hind limb extensor phase, and the number of animals
protected from convulsions was noted. In this study, the
animals were administered 30 mg kg-1 (body mass) dose
of the test drug and 25 mg kg-1 (body mass) dose of
standard drug phenytoin. The test and standard compounds
were suspended in 10% tween-20 and administered intra-
peritoneally 30 min prior to testing. The control group
animals, however, received the same volume of vehicle
(1% carboxymethyl cellulose) and results are reported in
11
12
13
14
50
15
0
Phenytoin
100
One-way ANOVA f
1859.1
df
17,90
P
\0.0001
n = 6 in each group
** p \ 0.0001 and * P \ 0.001 compared against the control group
123

252
Med Chem Res (2011) 20:245–253
activity among all compounds. Among the halogen (elec-
tron-withdrawing group) substituted compounds only com-
poundhavingfluorideortrifluoromethylgroupanduptosome
extent chloride group (compound 1 showed anxiolytic and
anticonvulsant activity) on R1 position showed significant
central nervous system activity, the possible reason could be a
fluorine atom are small in size, lipophilic in nature and ability
to form stronghydrogen bond; moreover, they have metabolic
stability under physiological condition (Shah and Westwell,
2007). Compound 7 having methyl (electron donating) group
on R1 position showed broad window of central nervous
system activity (antidepressant, anxiolytic and anticonvul-
sant). Though the exact reason behind this abnormality is not
known but the metabolic conversion of 4-methylphenyl to 4-
methoxyphenyl group cannot be ignored as the possible rea-
son (Misra et al., 1973: Sharma and Dandiya, 1962) and
compound 14 having sulphonyl chloride group on R1 position
andsulphonamidegrouponRpositionalsoshowedsignificant
CNS (antidepressant, anxiolytic and anticonvulsant).
Table 7 Anticonvulsant activity of 2-amino-5-sulphanyl-1,3,4-thia-
diazole derivatives: pentylenetetrazole-induced-clonic convulsion
Compounds
Onset of convulsions in s
(mean SEM)
Death
Positive control
48.25 0.01
4/6
6/6
1/6
2/6
3/6
2/6
1/6
2/6
1/6
3/6
2/6
0/6
3/6
2/6
3/6
1/6
0/6
Negative control
48.00 0.01
1
151.30 0.12*
63.60 0.00
2
3
71.90 0.01*
70.25 0.02
4
5
171.25 0.14*
101.26 0.02**
170.26 0.03**
101.26 0.13
126.20 0.14
180.25 0.13*
106.70 0.01
99.90 0.13
6
7
8
9
10
11
12
13
125.20 0.11**
175.20 0.01**
No convulsion
Although the exact mechanism of the title compounds
on central nervous system is not known but involvement of
the GABAergic system cannot be ruled out, partly may be
due to its action on the HPA (hypothalamic-pituitary-
adrenal) axis. However, further studies are needed to elu-
cidate the same by observing its effect on neurotransmitter
levels in brain (Shalam et al., 2007; Milan, 2003).
14
Diazepam
One-way ANOVA 2380.3
f
df
17,90
P
0.0001
Finally, we may conclude that the diaryl substitution
have made on thiadiazole nucleus that is essential for
providing optimum lipophilic character for synthesized
compounds showing appreciable biological activity.
Compounds 1, 5, 7, 10 and 14 can be selected for further
studies since they showed CNS activity (antidepressant,
anxiolytic and anticonvulsant) comparable to standard
drug, fluoxetine HCl, phenytoin and diazepam.
n = 6 in each group
** p \ 0.0001, * p \ 0.001 compared against control
Results and discussion
The synthesis of the new substituted 2-amino-5-sulfanyl-
1,3,4-thiadiazole derivatives (1–15) is depicted in
Scheme 1. The title compounds were synthesized through
nucleophilic substitution reaction. In first slop step, for-
mation of nucleophile in the presence of strong base that
further react with aryl halide to form intermediate. The
important feature of this intermediate is the ability of the
negative charge to be delocalized into electron-withdraw-
ing groups. In the second step, the leaving group is elim-
inated to regenerate the title compounds. The structure of
the synthesized compounds was fully characterized by
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