Pharmacological screening of some newly synthesized triazoles for H1 receptor antagonist activity

Article abstract of DOI:10.1007/s00044-017-1928-4

The present work deals with the pharmacological screening of some newly synthesized triazoles. A series of 1,2,4-triazoles have been synthesized using benzoic acid or 4-chloro benzoic acid as the starting materials. The synthesized compounds were characterized by physical and spectral analysis viz., Fourier transform infrared spectroscopy, ¹H nuclear magnetic resonance, ¹³C nuclear magnetic resonance, Gas Chromatography-Mass Spectrometry and elemental analysis Carbon, Hydrogen and Nitrogen analysis in order to confirm the structure. Acute toxicity studies were carried out in accordance with the Organization for Economic Co-operation and Development guideline 425. The compounds were not found to be lethal even at a dose level of 2000 mg/kg. Pharmacological evaluation was done following three intact animal experiments and one experiment on the isolated tissue. Results of the study indicated that the compound 7bi and 7bj protected up to 60% against histamine-induced dyspnea. Antihistaminic nature of the test compounds 7bi, 7bj, 7ai, and 7bk were also confirmed by the loss of catalepsy after the administration of clonidine (1%, s.c.). During experiments on isolated tissue, suppression of dose-response curve of histamine indicates a noteworthy denouement in favor of the said effect.

Full text of DOI:10.1007/s00044-017-1928-4

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res
DOI 10.1007/s00044-017-1928-4
ORIGINAL RESEARCH
Pharmacological screening of some newly synthesized triazoles for
H receptor antagonist activity
1
1 ●
1
Jeetendra Kumar Gupta Pradeep Mishra
Received: 21 January 2017 / Accepted: 22 May 2017
©
Springer Science+Business Media New York 2017
●
●
●
Abstract The present work deals with the pharmacological
Keywords Triazoles Amines Antihistaminic
screening of some newly synthesized triazoles. A series of
H antagonist
1
1
4
,2,4-triazoles have been synthesized using benzoic acid or
-chloro benzoic acid as the starting materials. The synthe-
sized compounds were characterized by physical and spec-
tral analysis viz., Fourier transform infrared spectroscopy,
H nuclear magnetic resonance, C nuclear magnetic reso-
Introduction
1
13
nance, Gas Chromatography-Mass Spectrometry and ele-
mental analysis Carbon, Hydrogen and Nitrogen analysis in
order to confirm the structure. Acute toxicity studies were
carried out in accordance with the Organization for Eco-
nomic Co-operation and Development guideline 425. The
compounds were not found to be lethal even at a dose level
of 2000 mg/kg. Pharmacological evaluation was done fol-
lowing three intact animal experiments and one experiment
on the isolated tissue. Results of the study indicated that the
compound 7bi and 7bj protected up to 60% against
histamine-induced dyspnea. Antihistaminic nature of the test
compounds 7bi, 7bj, 7ai, and 7bk were also confirmed by
the loss of catalepsy after the administration of clonidine
The interests in heterocyclic compounds are growing day-
by-day, as they are occupying a significant role in our
biological system. Naturally occurring heterocyclic com-
pounds are extremely common as, for example, DNA,
RNA, enzyme cofactors, plant pigments, hemoglobin,
vitamins, and alkaloids etc. (Saini et al. 2013). Especially
the chemistry of heterocyclic compounds containing three
nitrogen atoms continue to be of interest on account of their
different biological activities (Martins et al. 2015). Among
heterocyclic compounds, triazoles are five membered
compounds having three nitrogen atoms at different posi-
tions. Most of the triazole containing compounds are bio-
logically active which attribute to the sense that they are
deep seated part of the biomolecular diversity (Al-Masoudi
et al. 2006; Asif 2014). In the last few decades, the phar-
macology of 1,2,4-triazoles and their analogues achieved
considerable relevance because of their wide range of bio-
logical importance (Godhani et al. 2015). The synthesis of
triazoles and their derivatives have acquired considerable
attention attributing to their medicinal and biological
importance. Compounds bearing 1,2,4-triazole possess a
variety of biological applications such as anti-inflammatory
(
1%, s.c.). During experiments on isolated tissue, suppres-
sion of dose-response curve of histamine indicates a note-
worthy denouement in favor of the said effect.
Electronic supplementary material The online version of this article
(
doi:10.1007/s00044-017-1928-4) contains supplementary material,
which is available to authorized users.
*
Jeetendra Kumar Gupta
(Pattan et al. 2012), hypoglycemic (Blank et al. 1972),
jkgupta81@rediffmail.com
anticonvulsant (Kamboj et al. 2015), antitubercular (Ozde-
mir et al. 2007), anxiolytic (Cetin and Gecibesler 2015),
antidepressant (Kane et al. 1988), antimicrobial (Mange
et al. 2013; Patil et al. 2013; Bhat et al. 2001; Gupta and
Jain 2015), antitumor (Romagnoli et al. 2010; Li et al. 2012;
Pradeep Mishra
pmishra51@rediffmail.com
1
Institute of Pharmaceutical Research, GLA University, Mathura
2
81406 Uttar Pradesh, India

Med Chem Res
Hou et al. 2011), anticancer (Bekircan et al. 2006), and
antihistaminic activities (Alagarsamy et al. 2006). A num-
ber of triazoles are used with significant importance and
clinical applications e.g., fluconazole, itraconazole, vor-
iconazole, triazolam, alprazolam, etizolam, furacylin and
ribavirin (Uygun et al. 2013). The incorporation of various
substituent into 1,2,4-triazole ring and its fusion with var-
ious heterocyclic systems have resulted in compounds with
enhanced activities. Amongst these, the mercapto and
amino substituted 1,2,4-triazoles occupy broad spectrum as
well as are also of great utility in preparative organic
chemistry (Shaker 2006). In continuation of our ongoing
studies of the chemistry of 1,2,4-triazole, herein we report
the synthesis of several amine linked triazoles. Terminal
amine functional groups are present in many antihistaminic
compounds (DeRuiter 2001). However, the primary struc-
tural differences involve the nature of the para aromatic ring
substituent and, more significantly, the nature of the term-
inal amine nitrogen substituent. Cyclizine and chlorcycli-
zine are the simplest examples of the N-methylpiperazines
sulfate (Chernyshev et al. 2006). The precipitate so obtained
was weighed and melting/boiling point determined.
Methyl benzoate (2a) Colorless liquid. This compound
(2a) was prepared from benzoic acid (1a) (0.1 mol, 12.2 g)
and methanol (100 mL) according to the general procedure.
The product obtained as colorless liquid. 9.5 g (70%); b.p.
198–201 °C; Fourier transform infra red (FTIR) (KBr) νmax:
−
1 1
3080, 2969, 1720, 1602, 1375, 1113, 745 cm ; H NMR
(DMSO-d , 400 MHz): δ = 7.88 (2H, m, H-2′, H-6′), 7.54
6
1
3
(3H, m, H-3′, H-4′, H-5′), 3.83 (3H, s, CH3); C NMR
(DMSO-d , 100 MHz): δ = 165.2 (C, C=O), 131.7 (CH, C-
6
4′), 130.4 (C, C-1′), 128.0 (CH, C-3′, C-5′), 124.5 (CH, C-
2′, C-6′), 48.2 (CH , O–CH ); Gas Chromatography-Mass
3
3
+
Spectrometry (GC-MS) m/z 136 [M ]; anal. calcd. for
C H O : C, 70.57; H, 5.92; found: C, 70.26; H, 5.89.
8
8 2
Methyl 4-chloro benzoate (2b) White solid (MeOH). This
compound (2b) was prepared from 4-chloro benzoic acid
(1b) (0.1 mol, 15.6 g) and methanol (100 mL) according to
the general procedure. The product obtained as white solid
was purified from methanol. 13.4 g (79%); m.p. 42–45 °C;
FTIR (KBr) νmax: 3056, 2955, 1717, 1589, 1386, 1120, 752
having antihistaminic (H antagonist) property. Nitrogen-
1
containing heterocyclic compounds, viz.: pemirolast and
azelastine, are also known for their similar action. In view
of the facts stated above, we synthesized a series of triazoles
for their significant biological activities.
−1 1
cm ; H NMR (DMSO-d , 400 MHz): δ = 7.96 (2H, d, J
6
= 8.08, H-2′, H-6′), 7.41 (2H, d, J = 8.04, H-3′, H-5′), 3.75
1
3
(
3H, s, CH3); C NMR (DMSO-d , 100 MHz): δ = 165.0
6
(C, C=O), 137.2 (C, C-4′), 128.6 (C, C-1′), 128.4 (CH, C-
Materials and methods
3′, C-5′), 126.3 (CH, C-2′, C-6′), 49.8 (CH , O–CH ); GC-
3 3
+
MS m/z 170 [M ]; anal. calcd. for C H ClO : C, 56.32; H,
8
7
2
All the chemicals and solvents used are of L.R. grade
procured from Merck, Sigma-Aldrich or Spectrochem. The
method for synthesis of the title compounds involves the
conversion of carboxylic acids to their corresponding esters,
then to hydrazides, and finally into triazoles via dithio-
carbazate salts (Upmanyu et al. 2011b, c). The triazoles then
reacted with chloroacetyl chloride and further treated with
the secondary amines in order to get the final product. The
route of synthesis for the triazoles was outlined in scheme
of synthesis (Figs. 1 and 2).
4.14; found: C, 56.52; H, 4.16.
Synthesis of acid hydraz ide (3a–b)
Compound (2) (0.1 mol) was taken in a round-bottom flask
with methanol (100 mL). Hydrazine hydrate (99%) (0.15
mol, 5.7 mL) was added drop wise with gentle stirring. The
reaction mixture was refluxed for 4–6 h. Excess of methanol
was distilled off under reduced pressure. The precipitated
hydrazide was dried and re-crystallized from methanol
(Zamani and Faghihi 2003).
Steps of synthesis
Synthesis of methyl ester (2a–b)
Benzohydrazide (3a) Off-white solid (MeOH). This
compound (3a) was prepared from methyl benzoate (2a)
(0.1 mol, 13.6 g) and methanol (100 mL) according to the
general procedure. The product obtained as off-white solid
was purified from methanol. 11.6 g (85.3%); m.p. 112–114
°C; FTIR (KBr) νmax: 3457, 3300, 3032, 1660, 1590, 685
The aromatic carboxylic acid (0.1 mol) was taken in a
round-bottom flask and dissolved in methanol (100 mL).
Concentrated sulphuric acid (2 mL) was added to it. The
mixture was refluxed for 6 h. Excess of methanol was then
distilled off at reduced pressure. After cooling, water was
added to the flask and extracted several times with carbon
tetrachloride. The organic layer was washed with 5%
sodium bicarbonate to remove unreacted acid. The solvent
was then distilled off after drying with exsiccated sodium
−1 1
cm ; H NMR (DMSO-d , 400 MHz): δ = 9.81 (1H, s,
6
NH), 7.88 (2H, m, H-2′, H-6′), 7.41 (3H, m, H-3′, H-4′, H-
1
3
5′), 4.46 (2H, s, NH2); C NMR (DMSO-d , 100 MHz):
6
δ = 166.2 (C, C=O), 133.1 (C, C-1′), 130.9 (CH, C-4′),
128.1 (CH, C-3′, C-5′), 126.9 (CH, C-2′, C-6′); GC-MS m/z

Med Chem Res
Fig. 1 Scheme of synthesis
+
1
36 [M ]; anal. calcd. for C H N O: C, 61.75; H, 5.92; N,
C H ClN O: C, 49.28; H, 4.14; N, 16.42; found: C, 49.08;
7 7 2
7
8
2
2
0.58; found: 61.68; H, 5.89; N, 20.52.
H, 4.12; N, 16.35.
4
-Chloro benzohydrazide (3b) Off-white solid (MeOH).
This compound (3b) was prepared from methyl 4-chloro
benzoate (2b) (0.1 mol, 17 g) and methanol (100 mL)
according to the general procedure. The product obtained as
off-white solid was purified from methanol. 15.6 g (92%);
m.p. 161–163 °C; FTIR (KBr) νmax: 3461, 3309, 3019,
Synthesis of potassium 3-aroyl dithiocarbazate (4a–b)
Potassium hydroxide (0.15 mol, 8.4 g) was mixed with etha-
nol (100 mL) in a flat bottom flask. The synthesized hydrazide
(0.1 mol) was transferred to the flask. Carbon disulfide (0.15
mol, 9 mL) was then added to it. The reaction mixture was
stirred for 16 h at room temperature. The product was filtered
off through whatman paper and washed with ether to remove
excess of carbon disulfide. Further the filtered product was
dried at room temperature (Cansiz et al. 2004). The salt, so
obtained was taken for the next step without further
654, 1597, 678 cm− ; H NMR (DMSO-d , 400 MHz): δ
1
1
1
6
=
9.87 (1H, s, NH), 7.87 (2H, d, J = 8.04, H-2′, H-6′), 7.45
1
3
(
2H, d, J = 8.04, H-3′, H-5′), 4.50 (2H, s, NH2); C NMR
(
DMSO-d , 100 MHz): δ = 165.1 (C, C=O), 136.1 (C, C-
6
4
2
′), 131.6 (CH, C-1′), 128.6 (CH, C-3′, C-5′), 128.1 (CH, C-
′, C-6′); GC-MS m/z 170 [M ]; anal. calcd. for
+

Med Chem Res
Fig. 2 Title compounds
purification. The formation of compounds, potassium salt of
mL) in 100 mL absolute ethanol was added to it. Refluxing
was done for 2–3 h. The gas coming out from out let was
tested for hydrogen sulfide by lead acetate paper. The whole
solution turned green. When the evolution of gas ceased, the
excess of alcohol was distilled off. After cooling, water was
added. With the aid of hydrochloric acid (1N), the pre-
cipitate was separated. The precipitate so formed was fil-
tered off and crystallization affected by hydro-alcoholic
solution (Jadhav et al. 2010).
3-benzoyl dithiocarbazate (4a) as well as 3-(4-chloro-ben-
zoyl) dithiocarbazate (4b) was confirmed by IR spectra
−1
(
characteristic peaks at 3320, 1640, 1230, and 1065 cm due
to N–H, C=O, C=S and C–N stretchings respectively).
Synthesis of 4-amino-3-mercapto-5-phenyl-1,2,4-triazole
(
5a–b)
Compound (4a–b) collected above was dissolved in little
portion of water in a round-bottom flask equipped with
condenser and an outlet. Hydrazine hydrate (0.2 mol, 7.6
4-Amino-3-mercapto-5-phenyl-1,2,4-triazole
white solid (EtOH). This compound (5a) was prepared
(5a) Off-

Med Chem Res
from potassium 3-aroyl dithiocarbazate (4a), hydrazine
hydrate (0.2 mol, 7.6 mL) and ethanol (100 mL) according
to the general procedure. The product obtained as off-white
solid was purified from ethanol. 13.8 g (71.9%); m.p.
m, H-2′, H-6′), 7.60 (3H, m, H-3′, H-4′, H-5′), 4.62 (2H, s,
1
3
CH2); C NMR (DMSO-d , 100 MHz): δ = 169.6 (C,
6
NHCO), 165.8 (C, C-5), 149.5 (C, C-3), 129.5 (CH, C-3′,
C-5′), 128.9 (CH, C-4′), 127.2 (CH, C-2′, C-6′), 125.3 (C,
+
2
1
1
3
1
05–207 °C; FTIR (KBr) νmax: 3488, 3062, 2555, 1542,
C-1′), 52.83 (CH ); GC-MS m/z 268 [M ]; anal. calcd. for
2
−1
1
485, 712 cm
;
H NMR (DMSO-d , 400 MHz): δ =
C H ClN OS: C, 44.70; H, 3.38; N, 20.85; found: C,
6
10
9
4
3.83 (1H, s, SH), 7.88 (2H, m, H-2′, H-6′), 7.54 (3H, m, H-
44.51; H, 3.36; N, 20.73.
1
3
′, H-4′, H-5′), 5.70 (2H, s, NH2); C NMR (DMSO-d6,
00 MHz): δ = 166.7 (C, C-5), 149.1 (C, C-3), 130.1 (CH,
C-4′), 128.2 (CH, C-3′, C-5′), 127.8 (CH, C-2′, C-6′), 125.7
4-Chloroacyl amino-3-mercapto-5-(4′-chloro)phenyl-1,2,4-
triazole (6b) Light brown solid (dioxane). This compound
(6b) was prepared from 4-amino-3-mercapto-5-(4′-chloro)
phenyl-1,2,4-triazole (5b) (0.1 mol, 22.7 g), chloroacetyl
chloride (0.11 mol, 8.75 mL) and dioxane (100 mL)
according to the general procedure. The product obtained as
light brown solid was purified from dioxane. 19.8 g
(65.3%); m.p. 201–203 °C; FTIR (KBr) νmax: 3292, 3110,
+
(
C, C-1′); GC-MS m/z 192 [M ]; anal. calcd. for C H N S:
8 8 4
C, 49.98; H, 4.19; N, 29.14; found: C, 49.87; H, 4.17; N,
2
9.06.
4
-Amino-3-mercapto-5-(4′-chloro)phenyl-1,2,4-triazole
(
5b) Off-white solid (EtOH). This compound (5b) was
prepared from potassium 3-aroyl dithiocarbazate (4b),
hydrazine hydrate (0.2 mol, 7.6 mL) and ethanol (100 mL)
according to the general procedure. The product obtained as
off-white solid was purified from ethanol. 14.5 g (64.1%);
m.p. 214–216 °C; FTIR (KBr) νmax: 3490, 3108, 2578,
−
1
1
2974, 2570, 1653, 1545, 1493, 702 cm
(DMSO-d , 400 MHz): δ = 13.93 (1H, s, SH), 9.61 (1H, s,
NH), 8.10 (2H, d, J = 8.52, H-2′, H-6′), 7.51 (3H, m, H-3′,
;
H NMR
6
1
3
H-5′), 4.70 (2H, s, CH ); C NMR (DMSO-d , 100 MHz):
2 6
−
1 1
1
595, 1478, 711 cm ; H NMR (DMSO-d , 400 MHz): δ
δ = 170.2 (C, NHCO), 165.9 (C, C-5), 148.8 (C, C-3),
6
=
13.87 (1H, s, SH), 8.10 (2H, d, J = 8.56, H-2′, H-6′), 7.87
130.5 (C, C-4′), 129.8 (CH, C-3′, C-5′), 128.5 (CH, C-2′, C-
1
3
+
(
2H, m, H-3′, H-5′), 5.70 (2H, s, NH2); C NMR (DMSO-
d6, 100 MHz): δ = 166.9 (C, C-5), 148.2 (C, C-3), 135.3
CH, C-4′), 129.3 (CH, C-3′, C-5′), 128.3 (CH, C-2′, C-6′),
6′), 124.7 (C, C-1′), 53.6 (CH
anal. calcd. for C10 Cl
2
); GC-MS m/z 302 [M ];
OS: C, 39.62; H, 2.66; N, 18.48;
H
N
4
8
2
(
found: C, 39.45; H, 2.64; N, 18.39.
+
1
24.4 (C, C-1′); GC-MS m/z 226 [M ]; Anal. Calcd. for
C H ClN S: C, 49.39; H, 3.11; N, 24.72; found: C, 49.26;
8
7
4
H, 3.10; N, 24.65.
Synthesis of 4-(substituted ethanoyl)-3-mercapto-5-phenyl-
1,2,4-triazole (7a–b)
Synthesis of 4-chloroacyl amino-3-mercapto-5-phenyl-
Compound (6a–b) (0.025 mol) was solubilized in very little
amount of dimethyl sulfoxide (DMSO) and then the solu-
tion was diluted with benzene (75 mL approx.) in a round-
bottom flask. Respective amine (0.025 mol) was added to
the mixture. Triethylamine (0.025 mol) was then added. The
reaction mixture was refluxed for 4–5 h. Benzene was dis-
tilled off under reduced pressure to collect the product. The
precipitate so obtained was washed several times with dis-
tilled water and re-crystallized with benzene (Upmanyu
et al. 2012).
1
,2,4-triazole (6a–b)
Compound (5a–b) (0.1 mol) was dissolved in dioxane
100 mL) in a two necked round-bottom flask equipped with
(
condenser and a glass stopper. Chloroacetyl chloride (0.11
mol, 8.75 mL) was added to it. The reaction mixture was
refluxed for an hour. The content was allowed to cool and
poured on crushed ice. The precipitated product was filtered
and repetitively washed with cold distilled water (Upmanyu
et al. 2011a).
Thin layer chromatography using silica gel G was used
to determine the purity of synthesized compounds. Melting
points were determined in open capillaries and are uncor-
rected. Infrared (IR) spectra in KBr phase were recorded by
4
-Chloroacyl
amino-3-mercapto-5-phenyl-1,2,4-triazole
(
6a) Light brown solid (dioxane). This compound (6a)
was prepared from 4-amino-3-mercapto-5-phenyl-1,2,4-
triazole (5a) (0.1 mol, 19.2 g), chloroacetyl chloride (0.11
mol, 8.75 mL) and dioxane (100 mL) according to the
general procedure. The product obtained as light brown
solid was purified from dioxane. 18.3 g (68%); m.p.
1
3
Shimadzu IR Affinity-1 FTIR spectrophotometer. C and
1
H NMR spectra were recorded on Bruker Avance II 400
NMR spectrometer using DMSO-d6 as solvent. Mass
spectra were recorded using direct inlet probe on Thermo
Scientific TSQ 8000 Gas Chromatograph—Mass Spectro-
meter. Elemental estimations were carried out on Thermo
Scientific (FLASH 2000) Elemental Analyzer.
1
82–184 °C; FTIR (KBr) ν : 3300, 3074, 2942, 2552,
max
1 1
640, 1538, 1490, 705 cm− ; H NMR (DMSO-d , 400
1
6
MHz): δ = 13.80 (1H, s, SH), 9.5373 (1H, s, NH), 7.82 (2H,

Med Chem Res
4
-(4′-Methyl-piperazin-1′-yl ethanoyl) amino-3-mercapto-5-
= 173.8 (C, NHCO), 166.8 (C, C-5), 149.4 (C, C-3), 137.3
(C, C-a′), 130.4 (CH, C-4′), 129.2 (CH, C-b′, C-f′), 128.4
(CH, C-3′, C-5′), 128.2 (CH, C-c′, C-e′), 128.1 (CH, C-2′,
phenyl-1,2,4-triazole (7ai) Brown solid (benzene). This
compound (7ai) was prepared from 4-chloroacyl amino-3-
mercapto-5-phenyl-1,2,4-triazole (6a) (0.025 mol, 6.72 g),
C-6′), 127.1 (CH, C-d′), 125.4 (C, C-1′), 62.8 (CH , C-e),
2
1
-methylpiperazine (0.025 mol, 2.8 mL), triethylamine
58.4 (CH , COCH ), 52.8 (CH , C-a, C-d), 52.7 (CH , C-b,
C-c); GC-MS m/z 408 [M ]; anal. calcd. for C H N OS:
21 24 6
2
2
2
2
+
(
0.025 mol, 3.5 mL) and benzene (75 mL) according to the
general procedure. The product obtained as brown solid was
purified from benzene. 6.39 g (77%); m.p. 153–155 °C;
C, 61.74; H, 5.92; N, 20.57; found: C, 61.90; H, 5.95; N,
20.73.
FTIR (KBr) νmax: 3300, 3116, 2945, 2598, 1637, 1532,
1 1
498, 1481, 1234 cm− ; H NMR (DMSO-d , 400 MHz): δ
1
4-(2′-Methyl-piperidin-1′-yl ethanoyl) amino-3-mercapto-5-
phenyl-1,2,4-triazole (7al) Brown solid (benzene). This
compound (7al) was prepared from 4-chloroacyl amino-3-
mercapto-5-phenyl-1,2,4-triazole (6a) (0.025 mol, 6.72 g),
2-methylpiperidine (0.025 mol, 3 mL), triethylamine (0.025
mol, 3.5 mL) and benzene (75 mL) according to the general
procedure. The product obtained as brown solid was pur-
ified from benzene. 5.79 g (70%); m.p. 172–174 °C; FTIR
(KBr) νmax: 3296, 3116, 2953, 2540, 1641, 1536, 1499,
6
=
13.85 (1H, s, SH), 9.82 (1H, s, CONH), 7.54 (5H, m,
Ar–H), 3.41 (2H, s, COCH ), 2.65 (8H, m, CH -piperaz.),
2
2
1
3
2
1
.42 (3H, s, CH3); C NMR (DMSO-d , 100 MHz): δ =
73.8 (C, NHCO), 166.7 (C, C-5), 149.1 (C, C-3), 130.1
6
(
CH, C-4′), 128.2 (CH, C-3′, C-5′), 127.8 (CH, C-2′, C-6′),
1
25.7 (C, C-1′), 58.0 (CH , COCH ), 55.7 (CH , C-b, C-c),
2 2 2
5
2.0 (CH , C-a, C-d), 46.1 (CH , C-e); GC-MS m/z 332
2
3
+
[
M ]; anal. calcd. for C H N OS: C, 54.20; H, 6.06; N,
15 20 6
−
1
1
2
5.28; found: C, 54.42; H, 6.10; N, 25.19.
1484, 1173 cm ; H NMR (DMSO-d , 400 MHz): δ =
6
13.85 (1H, s, SH), 9.82 (1H, s, CONH), 7.62 (5H, m,
4
-(4′-Methyl-piperidin-1′-yl ethanoyl) amino-3-mercapto-5-
Ar–H), 3.39 (2H, s, COCH ), 1.94 (9H, m, CH, CH ), 1.17
2
2
1
3
phenyl-1,2,4-triazole (7aj) Brown solid (benzene). This
compound (7aj) was prepared from 4-chloroacyl amino-3-
mercapto-5-phenyl-1,2,4-triazole (6a) (0.025 mol, 6.72 g),
(3H, s, CH3); C NMR (DMSO-d , 100 MHz): δ = 173.3
6
(C, NHCO), 166.1 (C, C-5), 148.9 (C, C-3), 131.3 (C, C-4′),
128.7 (CH, C-3′, C-5′), 127.7 (CH, C-2′, C-6′), 125.3 (C, C-
1′), 59.2 (CH , COCH ), 56.1 (CH , C-e), 50.8 (CH, C-a),
4
-methylpiperidine (0.025 mol, 3 mL), triethylamine
2
2
2
(
0.025 mol, 3.5 mL) and benzene (75 mL) according to the
34.3 (CH , C-d), 24.9 (CH , C-c), 24.0 (CH , C-b), 18.2
2 2 2
+
general procedure. The product obtained as brown solid was
(CH , C-f); GC-MS m/z 331 [M ]; anal. calcd. for
3
purified from benzene. 6.12 g (74%); m.p. 142–144 °C;
C H N OS: C, 57.98; H, 6.39; N, 21.13; found: C, 58.21;
1
6 21 5
FTIR (KBr) νmax: 3282, 3140, 2974, 2580, 1620, 1502,
H, 6.43; N, 21.24.
1 1
498, 1458, 1165 cm− ; H NMR (DMSO-d , 400 MHz): δ
1
6
=
13.84 (1H, s, SH), 9.81 (1H, s, CONH), 7.55 (5H, m,
4-(Pyrrolidin-1′-yl ethanoyl) amino-3-mercapto-5-phenyl-
1,2,4-triazole (7am) Brown solid (benzene). This com-
pound (7am) was prepared from 4-chloroacyl amino-3-
mercapto-5-phenyl-1,2,4-triazole (6a) (0.025 mol, 6.72 g),
pyrrolidine (0.025 mol, 2.1 mL), triethylamine (0.025 mol,
3.5 mL) and benzene (75 mL) according to the general
procedure. The product obtained as brown solid was pur-
ified from benzene. 4.99 g (66%); m.p. 135–137 °C; FTIR
(KBr) νmax: 3306, 3096, 2955, 2571, 1660, 1512, 1493,
Ar–H), 3.40 (2H, s, COCH ), 1.91 (9H, m, CH, CH ), 1.20
2
2
1
3
(
(
4
3H, s, CH ); C NMR (DMSO-d , 100 MHz): δ = 174.6
3. 6
C, NHCO), 166.6 (C, C-5), 148.5 (C, C-3), 130.1 (CH, C-
′), 129.1 (CH, C-3′, C-5′), 127.1 (CH, C-2′, C-6′), 125.1
C, C-1′), 59.1 (CH , COCH ), 52.8 (CH , C-a, C-e), 34.4
(
(
2
2
2
CH , C-b, C-d), 30.6 (CH, C-c), 23.1 (CH , C-f); GC-MS
2
3
+
m/z 331[M ]; anal. calcd. for C H N OS: C, 57.98; H,
1
6 21 5
6
.39; N, 21.13; found: C, 58.15; H, 6.42; N, 21.22.
−
1
1
1
489, 1198 cm ; H NMR (DMSO-d , 400 MHz): δ =
6
4
-(4′-Benzyl-piperazin-1′-yl ethanoyl) amino-3-mercapto-5-
13.85 (1H, s, SH), 9.82 (1H, s, CONH), 7.79 (5H, m,
phenyl-1,2,4-triazole (7ak) Brown solid (benzene). This
compound (7ak) was prepared from 4-chloroacyl amino-3-
mercapto-5-phenyl-1,2,4-triazole (6a) (0.025 mol, 6.72 g),
Ar–H), 3.38 (2H, s, COCH ), 2.65 (2 × 2H, t, H-a′, H-d′),
2
1
3
1.76 (2 × 2H, m, H-b′, H-c′); C NMR (DMSO-d , 100
6
MHz): δ = 174.8 (C, NHCO), 166.1 (C, C-5), 148.1 (C, C-
3), 130.9 (CH, C-4′), 129.1 (CH, C-3′, C-5′), 128.1 (CH, C-
2′, C ), 124.9 (C, C-1′), 58.4 (CH , COCH ), 54.1 (CH , C-
1
-benzylpiperazine (0.025 mol, 4.4 mL), triethylamine
(
0.025 mol, 3.5 mL) and benzene (75 mL) according to the
6
′
2
2
2
+
general procedure. The product obtained as brown solid was
a, C-d), 23.8 (CH , C-b, C-c); GC-MS m/z 303 [M ]; anal.
2
purified from benzene. 6.54 g (64%); m.p. 210–213 °C;
calcd. for C H N OS: C, 55.42; H, 5.65; N, 23.08; found:
1
4 17 5
FTIR (KBr) νmax: 3301, 3124, 2957, 2591, 1612, 1512,
C, 55.19; H, 5.62; N, 22.98.
1 1
469, 1491, 1236 cm− ; H NMR (DMSO-d , 400 MHz): δ
1
6
=
13.83 (1H, s, SH), 9.81 (1H, s, CONH), 7.55 (2 × 5H, m,
4-(4′-Methyl-piperazin-1′-yl ethanoyl) amino-3-mercapto-5-
(4′-chloro) phenyl-1,2,4-triazole (7bi) Brown solid (ben-
zene). This compound (7bi) was prepared from 4-
Ar–H), 3.79 (2H, s, CH –Ar), 3.38 (2H, s, COCH ), 2.46
2
2
1
3
(
8H, m, CH -piperaz.); C NMR (DMSO-d , 100 MHz): δ
2 6

Med Chem Res
chloroacyl
amino-3-mercapto-5-(4′-chloro)phenyl-1,2,4-
d, J = 9.2, H-3′, H-5′), 7.48 (5H, m, Ar–H), 3.72 (2H, s,
CH –Ar), 3.29 (2H, s, COCH ), 2.45 (8H, m, CH -
triazole (6b) (0.025 mol, 7.57 g), 1-methylpiperazine (0.025
mol, 2.8 mL), triethylamine (0.025 mol, 3.5 mL) and ben-
zene (75 mL) according to the general procedure. The
product obtained as brown solid was purified from benzene.
2
2
2
1
3
piperaz.); C NMR (DMSO-d , 100 MHz): δ = 175.1 (C,
6
NHCO), 166.9 (C, C-5), 148.8 (C, C-3), 137.3 (C, C-a′),
135.1 (C, C-4′), 133.3 (CH, C-3′, C-5′), 129.2 (CH, C-b′, C-
f′), 128.2 (CH, C-c′, C-e′), 128.1 (CH, C-2′, C-6′), 127.1
(CH, C-d′), 124.4 (C, C-1′), 62.7 (CH , C-e), 59.2 (CH ,
6
3
.88 g (75%); m.p. 184–187 °C; FTIR (KBr) νmax: 3246,
149, 2937, 2586, 1637, 1530, 1498, 1479, 1095 cm ; H
−1 1
2
2
NMR (DMSO-d , 400 MHz): δ = 13.90 (1H, s, SH), 9.87
COCH ), 52.8 (CH , C-b, C-c), 52.7 (CH , C-a, C-d); GC-
2 2 2
MS m/z 442 [M ]; anal. calcd. for C H ClN OS: C,
21 23 6
56.94; H, 5.23; N, 18.97; found: C, 57.20; H, 5.25; N,
19.05.
6
+
(
(
(
(
1H, s, CONH), 8.35 (2 × 1H, d, J = 9.1, H-2′, H-6′), 7.74
2 × 1H, d, J = 9.2, H-3′, H-5′), 3.30 (2H, s, COCH ), 2.74
2
1
3
8H, m, CH -piperaz.), 2.39 (3H, s, CH ); C NMR
2
3
DMSO-d6, 100 MHz): δ = 176.1 (C, NHCO), 166.8 (C, C-
5
), 148.2 (C, C-3), 135.3 (C, C-4′), 129.5 (CH, C-3′, C-5′),
4
(
-(2′-Methyl-piperidin-1′-yl ethanoyl) amino-3-mercapto-5-
4′-chloro) phenyl-1,2,4-triazole (7bl) Brown solid (ben-
zene). This compound (7bl) was prepared from 4-
chloroacyl amino-3-mercapto-5-(4′-chloro)phenyl-1,2,4-
1
28.5 (CH, C-2′, C-6′), 124.6 (C, C-1′), 59.8 (CH2,
COCH ), 55.3 (CH , C-b, C-c), 52.2 (CH , C-a, C-d), 49.4
2
2
2
+
(
CH , C-e); GC-MS m/z 366 [M ]; anal. calcd. for
3
C H ClN OS: C, 49.11; H, 5.22; N, 22.91; found: C,
1
5
19
6
triazole (6b) (0.025 mol, 7.57 g), 2-methylpiperidine (0.025
mol, 3 mL), triethylamine (0.025 mol, 3.5 mL), and benzene
4
9.23; H, 5.25; N, 22.81.
(
75 mL) according to the general procedure. The product
4
-(4′-Methyl-piperidin-1′-yl ethanoyl) amino-3-mercapto-5-
obtained as brown solid was purified from benzene. 5.58 g
(
4′-chloro) phenyl-1,2,4-triazole (7bj) Brown solid (ben-
(61%); m.p. 166–169 °C; FTIR (KBr) νmax: 3289, 3137,
zene). This compound (7bj) was prepared from 4-
Chloroacyl amino-3-mercapto-5-(4′-chloro)phenyl-1,2,4-
triazole (6b) (0.025 mol, 7.57 g), 4-methylpiperidine (0.025
mol, 3 mL), triethylamine (0.025 mol, 3.5 mL) and benzene
−
1 1
2
(
961, 2581, 1639, 1531, 1489, 1488, 1179 cm ; H NMR
DMSO-d , 400 MHz): δ = 13.88 (1H, s, SH), 9.85 (1H, s,
6
CONH), 8.71 (2H, d, J = 9.1, H-2′, H-6′), 7.62 (2H, d, J =
.1, H-3′, H-5′), 3.29 (2H, s, COCH ), 1.96 (9H, m, CH,
9
2
(
75 mL) according to the general procedure. The product
1
3
CH ), 1.18 (3H, s, CH ); C NMR (DMSO-d , 100 MHz):
δ = 174.1 (C, NHCO), 166.6 (C, C-5), 148.5 (C, C-3),
1
6
5
2
3
6
obtained as brown solid was purified from benzene. 5.94 g
(
2
65%); m.p. 176–178 °C; FTIR (KBr) νmax: −3278, 3134,
34.1 (C, C-4′), 130.1 (CH, C-3′, C-5′), 128.1 (CH, C-2′, C-
1
1
974, 2578, 1620, 1502, 1477, 1451, 1165 cm ; H NMR
′), 124.4 (C, C-1′), 58.4 (CH , COCH ), 56.2 (CH , C-e),
2
2
2
(
DMSO-d , 400 MHz): δ = 13.93 (1H, s, SH), 9.86 (1H, s,
6
0.9 (CH, C-a), 34.4 (CH , C-d), 24.3 (CH , C-c), 24.1
2
2
CONH), 8.28 (2 × 1H, d, J = 9.1, H-2′, H-6′), 7.76 (2 ×
H, d, J = 9.2, H-3′, H-5′), 3.30 (2H, s, COCH ), 1.90 (9H,
+
(
CH , C-b), 18.9 (CH , C-f); GC-MS m/z 365 [M ]; anal.
2 3
1
2
calcd. for C H ClN OS: C, 52.52; H, 5.51; N, 19.14;
found: C, 52.80; H, 5.54; N, 19.20.
1
3
16 20
5
m, CH, CH ), 1.19 (3H, s, CH ); C NMR (DMSO-d6,
2
3
1
00 MHz): δ = 174.2 (C, NHCO), 166.9 (C, C-5), 148.2 (C,
C-3), 135.3 (C, C-4′), 129.3 (CH, C-3′, C-5′), 127.3 (CH, C-
′, C-6′), 124.4 (C, C-1′), 59.7 (CH , COCH ), 52.9 (CH ,
2
4-(Pyrrolidin-1′-yl
ethanoyl)
amino-3-mercapto-5-(4′-
2
2
2
C-a, C-e), 34.2 (CH , C-b, C-d), 30.3 (CH, C-c), 23.8 (CH ,
C-f); GC-MS m/z 365 [M ]; anal. calcd. for
chloro) phenyl-1,2,4-triazole (7bm) Brown solid (ben-
zene). This compound (7bm) was prepared from 4-
2
3
+
C H ClN OS: C, 52.52; H, 5.51; N, 19.14; found: C,
chloroacyl
triazole (6b) (0.025 mol, 7.57 g), pyrrolidine (0.025 mol,
.1 mL), triethylamine (0.025 mol, 3.5 mL), and benzene
amino-3-mercapto-5-(4′-chloro)phenyl-1,2,4-
1
6
20
5
5
2.35; H, 5.49; N, 19.05.
2
4
-(4′-Benzyl-piperazin-1′-yl ethanoyl) amino-3-mercapto-5-
(75 mL) according to the general procedure. The product
obtained as brown solid was purified from benzene. 6.42 g
(76%); m.p. 124–127 °C; FTIR (KBr) νmax: 3289, 3116,
(
4′-chloro) phenyl-1,2,4-triazole (7bk) Brown solid (ben-
zene). This compound (7bk) was prepared from 4-
chloroacyl amino-3-mercapto-5-(4′-chloro)phenyl-1,2,4-
−
1 1
2962, 2586, 1671, 1522, 1487, 1465, 1211 cm ; H NMR
triazole (6b) (0.025 mol, 7.57 g), 1-benzylpiperazine (0.025
mol, 4.4 mL), triethylamine (0.025 mol, 3.5 mL) and ben-
zene (75 mL) according to the general procedure. The
product obtained as brown solid was purified from benzene.
(DMSO-d , 400 MHz): δ = 13.86 (1H, s, SH), 9.87 (1H, s,
CONH), 8.45 (2H, d, J = 9.2, H-2′, H-6′), 7.57 (2H, d, J =
6
9.2, 3′, H-5′), 3.2880 (2H, s, COCH ), 2.59 (2 × 2H, t, H-a′,
2
1
3
H-d′), 1.71 (2 × 2H, m, H-b′, H-c′); C NMR (DMSO-d6,
100 MHz): δ = 175.1 (C, NHCO), 166.1 (C, C-5), 148.2 (C,
C-3), 135.2 (C, C-4′), 130.9 (CH, C-3′, C-5′), 128.4 (CH, C-
2′, C-6′), 125.1 (C, C-1′), 59.1 (CH , COCH ), 54.4 (CH ,
8
3
.08 g (73%); m.p. 192–194 °C; FTIR (KBr) νmax: 3286,
142, 2965, 2582, 1620, 1516, 1489, 1472, 1236 cm ; H
−1 1
NMR (DMSO-d , 400 MHz): δ = 13.87 (1H, s, SH), 9.87
6
2
2
2
+
(
1H, s, CONH), 8.19 (2H, d, J = 8.8, H-2′, H-6′), 7.59 (2H,
C-a, C-d), 23.6 (CH , C-b, C-c); GC-MS m/z 337 [M ];
2

Med Chem Res
anal. calcd. for C H ClN OS: C, 49.77; H, 4.77; N,
(150–200 g) were maintained at 25 ± 2 °C, with relative
humidity 45–50%, under 12 h of light/dark cycle for 3 days
in order to normalize their biorhythm. Animals were fed
with standard animal diet and water ad libitum. Prior to
dosing, rats were fasted overnight but allowed water ad
libitum. The test compounds were administered through
oral route as per guidelines set by the Organization for
Economic Co-operation and Development (OECD). The
referred dose (initial dose 175 mg/kg and limit dose 2000
mg/kg) of the test drug was given in accordance with OECD
guideline 425 (Viswanatha et al. 2012). It is also known as
Up-and-Down procedure, which is of cardinal value in
reducing the number of animals required in LD50 study.
Animals were dosed, one at a time and depending upon the
outcome, the dose for the next animal was adjusted. The
animals were observed for 24 h and thereafter for 14 days.
The observed morbidity and mortality was analyzed
through AOT425StatPgm. All the synthesized compounds
were found to be non-lethal even at 2000 mg/kg dose level.
1
4
16
5
2
0.73; found: C, 49.92; H, 4.79; N, 20.81.
Pharmacological screening
Screening of the synthesized compounds was carried out on
experimental animals. There are three types of screening
viz.: simple screening, blind screening, and programmed
screening. In this study, programmed screening has been
carried out. Programmed screening generally used when a
newly synthesized drug of specific type is to be screened for
some pharmacological action. The screening protocol was
reviewed and approved by the Institutional Animal Ethical
Committee, Institute of Pharmaceutical Research, GLA
University Mathura, India [Approval No: 1260/Po/Ere/S/
0
9/CPCSEA], constituted in accordance with the guidelines
of the Committee for the Purpose of Control and Super-
vision of Experiments on Animals, Government of India,
New Delhi.
Screening of chemical or pharmacological agent starts
with an initial procedure of toxicity study, known as lethal
dose (LD ) study. The assessment of LD (the dose that
kills 50% of the test animal population) gives an idea about
the safe dose at which pharmacological experiments can be
started.
Effect of the test compound on animal behavior
5
0
50
This test was undertaken with a view to observe any
unwanted or any substantial change in the animal behavior.
The experiment involved test drug administration through
intraperitoneal route in swiss albino mice (30–35 g). Mice
of either sex were fasted overnight under laboratory con-
dition and allowed for water ad libitum. The selected dose
LD50 study
1
00 mg/kg (not more than 1/10 LD ) was given and the
50
It involves determination of median LD50 within 24 h post
treatment of the test drug. Healthy albino wistar rats
change in behavior was noticed in the open arena (Donoso
and Broitman 1979). Data are presented in Table 1.
Table 1 Effect of the test compound on animal behavior
Compound
Behavior recorded in open arena for 1 h
Staggering gait Rearing Grooming Gross
Palpebral
closure
Visual
placing
reflex
Righting
reflex
Thirst Appetite Defecation
locomotor
activity
7
7
7
7
7
7
7
7
7
7
ai
+
+
+
+
0
0
+
0
− −
+
0
+
+++
+++
+++
+++
+++
+++
+++
+++
+++
+++
+++
+
+
+
0
+
0
aj
+
+
0
−
+
+
+
+
+
0
ak
al
0
0
0
+
+
+
0
0
0
++
0
+
am
bi
0
0
0
+
+
+
+
+
0
+
+
0
0
0
− − −
++
+
0
+
++
+
+
+
+
+
+
+
bj
0
+
0
− −
−
0
+
bk
bl
0
0
+
++
+
+
+
0
0
0
0
+
bm
0
+
+
0
0
+
+
Normal
control
+
0
0
++
+
+
−
− − effect reduced strongly, − − effect reduced moderately, − effect reduced slightly, 0 no effect, + present with slight effect, ++ present with
moderate effect, +++ present with strong effect

Med Chem Res
Table 2 Effect of the test drug on clonidine-induced catalepsy
Clonidine-induced catalepsy: histamine mediated behavior
Treatment
Duration of catalepsy
Clonidine is an alpha adrenergic agonist, but when admi-
nistered intra-peritoneally in mice, it triggers histamine
release and produces catalepsy, which is a condition in
which the test animal has tendency to retain the imposed
posture for at least 10 s. The clonidine-induced catalepsy
(mean ± SEM) in seconds at
1
5 min
30 min
Vehicle (i.p.)
89.17 ± 1.88 75.00 ± 1.59
Pheniramine maleate (10 mg/kg, i.p.) 28.67 ± 1.92** 16.00 ± 1.80**
7
ai
48.67 ± 1.37** 30.5 ± 1.48**
53.17 ± 1.37* 68.67 ± 2.23*
53.83 ± 0.87 69.67 ± 1.54
54.33 ± 1.17 69.83 ± 1.19
54.00 ± 1.39 72.00 ± 1.12
31.17 ± 1.35** 18.17 ± 1.19**
46.33 ± 1.20** 21.00 ± 1.18**
53.33 ± 0.88* 68.00 ± 1.44*
55.00 ± 1.92 70.67 ± 0.88
54.17 ± 1.25 70.83 ± 1.07
can be attenuated by H anti-histaminics (Taur and Patil
1
2
011) and it is an indirect method to screen antihistaminic
7aj
7ak
7al
effect of test compounds.
Bar test was used to study the effect of the synthesized
compounds. Swiss albino mice of average body weight
7am
7bi
7bj
(
25–30 g) were divided into 12 groups, one group for vehicle
control, another group for pheniramine treatment and
remaining ten groups for the test compounds. Clonidine
7
7
7
bk
bl
(
dose: 1 mg/kg, s.c.) was administered to the mice of all
groups after 30 min of the test drug administration. An ele-
vated bar of height 3.5 cm was used, on which fore paw of
each mouse was placed and duration for which the animal
maintains the imposed posture was noted through stop
watch. The dose of the test compound was selected on the
basis of acute toxicity study. Since the optimal test dose
during LD50 study was 2000 mg/kg body weight, hence the
safe pharmacological dose should not be more than one-tenth
of the LD . The selected dose was also verified through a
bm
All values are expressed as mean ± SEM, where n = 6 per group. Data
analyzed by one way ANOVA followed by Dunnett’s test. Significant
when compared with control
*
p < 0.05; **p < 0.01
Table 3 Effect of the test drugs on histamine-induced PCD end point
time
5
0
Treatment
Pre-convulsive dyspnea end point
time (in seconds)
% Protection
pilot study before the main test. Effect of the test compounds
on clonidine-induced catalepsy is shown in Table 2.
Vehicle control 102.83 ± 2.34
–
7
7
7
7
7
ai
240.33 ± 3.79**
112.00 ± 2.00
108.33 ± 1.72
111.50 ± 2.32
105.17 ± 2.12
351.83 ± 2.81**
261.50 ± 2.68**
112.83 ± 3.14*
112.16 ± 1.51
105.67 ± 1.99
464.50 ± 2.68**
57.21
8.18
5.07
7.77
2.22
70.77
60.07
8.86
8.32
2.68
77.86
Histamine-induced anaphylactic shock
aj
ak
al
Anaphylactic shock induced by histamine aerosol is an
allergic response mainly characterized by bronchospasm
and fainting of animal. It is a well established method for
am
screening of antihistaminic (type-H ) drugs (Sadek et al.
7bi
1
2
013). In this experiment, bronchospasm was induced in
7bj
overnight fasted guinea pigs. Guinea pigs of either sex and
average body weight were selected for this experiment.
Animals were divided into 12 groups as; Group-1: Vehicle
control, Group-2: Standard (Pheniramine treated, Dose:
7bk
7bl
7bm
Pheniramine
1
1
0 mg/kg) and Group-(3 to 12): test drugs treated (dose:
00 mg/kg body weight).
%
Protection = [(T
T
–T
C
)/T
T
] × 100; where, T
T
: PCD end point time
for the test drug; T
C
: PCD end point time for vehicle control. All
Bronchospasm was induced in guinea pig with the help
of 1% histamine aerosol. This study was carried out in a
values are expressed as mean ± SEM, where n = 6 per group. Data
analyzed by one way ANOVA followed by Dunnett’s test. Significant
when compared with control
transparent chamber made of perplex glass (dimension—
3
*p < 0.05; **p < 0.01
2
4 × 14 × 24 cm ). Guinea pig placed in the transparent
glass chamber was exposed to histamine aerosol under
2
constant pressure (1 kg/cm ). End point time for pre-
convulsive dyspnea (PCD) was determined from the time
of aerosol exposure. As soon as the PCD commenced, the
guinea pig was removed from the aerosol chamber and
exposed to fresh air for recovery. Effect of the test com-
pounds on pre-convulsive dyspnea end point time is pre-
sented in Table 3.
Study on isolated tissue: isolated guinea pig ileum
preparation
Overnight fasted guinea pig was sacrificed and abdomen
was opened. Pieces of ileum (2–3 cm long) were isolated.
The isolated pieces of ileum were quickly transferred to

Med Chem Res
Table 4 Effect of the test drug on isolated tissue preparation
S.N
Conc. of the test Log [A] % Inhibition in DRC of histamine after the exposure of test drug [histamine used
drug [A] in µM
(1.6 mL, strength 1 mg/mL)]
7
ai 7aj 7ak 7al
7am
7bi
7bj
7bk
7bl
7bm Pheniramine
1
10
20
1.00
1.30
1.60
1.90
2.20
2.25
29.76 18.31 12.98
30.55 19.09 14.51
4.57
5.35
5.35 41.99 32.83 41.17 16.02 9.15 43.50
8.40 43.50 34.34 42.75 18.31 12.22 60.31
2
3
40
32.05 22.89 16.80 13.73 24.29 55.73 45.04 58.78 39.70 24.43 70.98
41.99 41.21 35.88 37.41 34.34 81.68 61.07 72.52 58.02 37.41 85.50
4
80
5
160
320
54.95 51.15 50.37 48.08 48.86 100
66.40 63.36 61.07 61.07 57.24 100
72.52 85.50 79.39 55.73 100.00
87.79 100.00 100.00 80.14 100.00
6
IC50 value
84.80 113.79 131.86 138.29 151.32
21.80 38.64 23.12 47.98 86.60 13.16
Petri dish containing tyrode (physiological salt solution)
under suitable aeration. The tissue was then mounted in
organ bath containing the same physiological salt solution
at 37 °C. A basal tension of 0.5 g was applied and the tissue
was allowed to stabilize for 30 min. The tissue was then
exposed to the test drugs and dose-response contractions
were recorded (Lin et al. 2012). Effect of the test com-
pounds on dose-response curve of histamine is given in
Table 4.
et al. 2010; Ghochikyan et al. 2016) shows the bands at
−
1
2743–2740, 1740–1743, and 1570–1586 cm
.
The compounds were tested on laboratory animals. In
order to explore acute toxicity, LD50 determination was
carried out. Effect of the test compound on animal behavior
was also observed at pharmacological dose level. Pre-
liminary screening showed that the compounds have anti-
histaminic (type-H ) activity. On the basis of studies on
1
experimental animals, the compounds were then tested on
isolated tissue. Among them, compound 7bi, 7bk, 7bj, and
7bl showed potential anti-histaminic action with IC50 of
Results and discussion
21.80, 23.12, 38.64, and 47.98 µM respectively. The refer-
ence drug pheniramine maleate showed an IC50 of 13.16
µM (Table 4). Experimental models (viz., clonidine-induced
catalepsy and histamine-induced bronchospasm) confirmed
The synthesis was accomplished as per the given scheme.
Aromatic carboxylic acids were converted into their
respective methyl esters and further into hydrazides.
Hydrazides were treated with carbon disulfide and alcoholic
potassium hydroxide in order to form their dithiocarbazate
salts. The salts were reacted with hydrazine and converted
into their respective 1,2,4-triazoles. The triazoles, so
obtained were reacted with chloracetyl chloride to give acyl
derivatives. These acyl derivatives were treated with the
amines (2°) to give the title compounds. Synthesized
compounds were characterized by various spectral and
the H receptor antagonist activity of the compounds. Our
1
studies showed that compounds containing 1-methyl
piperazine, 4-methyl piperidine, and 1-benzyl piperazine
at the terminal position of the acyl derivative of the triazole
ring exhibited significant antihistaminic property. The
compounds 7bk and 7aj showed moderate inhibition of
catalepsy, while compounds 7bi, 7bj, and 7ai exhibited
significant anti-cataleptic effect (Table 2). In case of
histamine-induced dyspnea model in guinea pig, the com-
pound 7bi, 7bj, and 7ai manifested potential protection
while 7bk showed moderate protection (Table 3). Among
the ten compounds, it was observed that the electron
withdrawing substituent, i.e., halogen (chloro-) substituted
compounds showed comparatively better activity. The
noteworthy denouement is the emergence of triazoles with
secondary amines as promising antihistaminic agents.
1
3
1
physical data i.e., C NMR, H NMR, FTIR spectroscopy,
1
3
GC-MS and elemental analysis. The C NMR spectra for
C and C of the 1,2,4-triazole ring were observed in the
3
5
range of δ 148–149 and 166–176 ppm, while as per reported
literature (Zamani and Faghihi 2003), they fall in the range
of δ 148–152 and 168–169 ppm. In H NMR spectra,
singlet of CONH and SH were seen in the range of δ
1
9
.83–9.88 and 13.85–14.03 ppm respectively. As per
reported literature (Hussain et al. 2008; Kochikyan et al.
2
6
010), the singlet of CONH and SH lie in the range of δ
.58–7.53 and 13.25–13.95 respectively. FTIR spectra
Conclusion
exhibited characteristic bands for S–H, C=O and C=N in
the range of 2540–2596, 1612–1671, and 1469–1519 cm
The present work addresses a new series of triazoles having
−
1
antihistaminic (H antagonist) property. A series of novel
1
respectively, however the reported literature (Kochikyan
triazoles were synthesized and their pharmacological

Med Chem Res
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evaluations carried out. A few of them showed potent
antihistaminic (type-H ) activity. The recorded percentage
1
9
protection by the test compounds against histamine-induced
pre-convulsive dyspnoea on guinea pig was observed.
When clonidine, a presynaptic alpha 2 receptor agonist was
administered intra-peritoneally in mice, it triggered hista-
mine release in the brain and produced catalepsy in mice.
The bar test was used to access the effect of the synthesized
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The field is further open for study. Preliminary findings
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Acknowledgements The authors are thankful to the GLA University
administration for providing research facilities for the present work.
The authors wish to thank SAIF-CIL Panjab University, Chandigarh
for spectral studies.
Compliance with ethical standards
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3H-1,2,4-triazole-3-thiones as potential antidepressant agents. J
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Conflict of interest The authors declare that they have no competing
interests.
Kochikyan TV, Samvelyan MA, Arutyunyan VS, Avetisyan AA,
Tamazyan RA, Aivazyan AG (2010) Synthesis of 1,2,4-triazole-
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4
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