Investigation of piperidine derivatives in ex vivo models of pain and platelet aggregation

Article abstract of DOI:10.1007/s12272-012-1112-9

Piperidine derivatives are known to exhibit analgesic activities and are likely to possess the ability to block the effects of prostaglandins through inhibition of downstream signaling pathways. The present study investigated the activity of five derivati

Full text of DOI:10.1007/s12272-012-1112-9

Arch Pharm Res Vol 35, No 11, 1953-1959, 2012
DOI 10.1007/s12272-012-1112-9
Investigation of Piperidine Derivatives in Ex Vivo Models of Pain and
Platelet Aggregation
Zafar Saeed Saify1, Huma Rasheed2, Nousheen Mushtaq3, Mehrun Nisa1, Shazia Haider1, Afshan Naz4,
Kaniz Fizza Azhar5, and Ghulam Abbas Miana6
2
1HEJ Research Institute of Chemistry, ICCBS, University of Karachi, Karachi 75270, Pakistan, Dr. Panjwani Center for
3
Molecular Medicine and Drug Research, ICCBS, University of Karachi, Karachi 75270, Pakistan, Department of Pharma-
ceutical Chemistry, Faculty of Pharmacy, University of Karachi, Karachi 75270, Pakistan, 4Biophysics Research Unit,
5
Department of Biochemistry, University of Karachi, Karachi 75270, Pakistan, PCSIR-Scientific Information Centre, PCSIR
6
Labs Campus, Sharah-e-Dr. Salimuzzaman Siddiqui, Karachi 75280, Pakistan, and Riphah Institute of Pharmaceutical
Sciences, Riphah International University, Islamabad, Pakistan
(Received January 10, 2011/Revised April 14, 2011/Accepted May 16, 2011)
Piperidine derivatives are known to exhibit analgesic activities and are likely to possess the
ability to block the effects of prostaglandins through inhibition of downstream signaling path-
ways. The present study investigated the activity of five derivatives (PD2-6) of 4-(4'-bromo-
phenyl)-4-piperidinol (PD1), against pain and platelet aggregation mediated by the release of
prostaglandins and thromboxane A2, respectively. The results showed that compound PD1
and its two phenacyl derivatives PD3 and PD5 exhibited a highly significant analgesic effect
(p < 0.01), whereas PD4 and PD6 also showed significant activity. PD3, the most active anal-
gesic compound when docked to the opioid receptor, had interactions between the oxygen of its
nitro group and the amino group of ARG 573, indicating a distance of 1.2563 Å. The antiplate-
let data showed that compound PD5 (4-(4'-bromo-phenyl)-4-hydroxy-1-[2-(2'',4''-dimethoxy-
phenyl)-2-oxo-ethyl]-piperidinium bromide) had an IC50 = 0.06 mM, which was the most active
compound, whereas PD3 was the second most active compound against platelet aggregating
factor-induced aggregation with an IC50 = 80 mM. Acetyl salicylic acid (IC50 = 150
used as a positive control.
µM) was
Key words: Pain, Opoid receptor, Platelet aggregation, Platelet activating factor
sess potent anti-HIV activity (Imamura et al., 2005).
Derivatives of 4-hydroxy-4-phenyl piperidine were also
INTRODUCTION
On the basis of structural modification, researchers reported as potent antihypertensive agents (Saeed et
have developed a number of piperidine derivatives al., 1998).
with significant biological effects including analgesic,
It was interesting to observe that some of the pi-
anti-inflammatory, antiangiogenic, antitumor, anti- peridine derivatives showed inhibitory activity against
depressant, antianxiety and antimalarial activities cyclooxygenase (COX), an enzyme responsible for the
(Miguel et al., 2002; Becker et al., 2005; Kordik et al., synthesis of prostaglandins which ultimately mediate
2006; Mushtaq et al., 2010; Ramachandran et al., 2011; pain, inflammation and platelet aggregation (Feng et
Saify et al., 2011; Thaler et al., 2012). The derivatives of al., 1992; Lawrence et al., 1994; Guo et al., 2000).
piperidine with aryl, alkyl and acyl substitutions pos-
The present study is the continuation of the synthesis
of new phenacyl derivatives of the piperidine molecule.
The derivatives of bromophenyl-4-piperidinol were
prepared by reactions with phenacyl halides and their
potential for analgesic and antiplatelet activities were
investigated.
Correspondence to: Zafar S. Saify, HEJ Research Institute of
Chemistry, ICCBS, University of Karachi, Karachi 75270, Paki-
stan
Tel: 92-21-465-1739, Fax: 92-21-465-1738
E-mail: zssaify@gmail.com, zssaify@iccs.edu
1953

1954
Z. S. Saify et al.
4-(4'-Bromo-phenyl)-4-hydroxy-1-[2-(2'',4''-dimeth-
oxy-phenyl)-2-oxo-ethyl]-piperidinium bromide
(PD5)
MATERIALS AND METHODS
Chemistry
Equimolar quantities of 4-(4-bromo-phenyl)-4-piper- Yield 51%, m.p. 226oC; IR max (KBr) cm−1: 3400, 2945,
ν
idinol and each of the other reactants were dissolved 1750, 1600, 1569, 1336, 1259, 542; UV λmax (MeOH)
in acetone (10-70 mL) separately. These were mixed nm: 301, 273, 227; 1H-NMR (MeOD, 500 MHz):
8.02
together in a round bottom f1ask and refluxed for 2-4 (d, 1H, = 2.82 Hz, -6''), 7.54-7.45 (m, 4H, -2', -6',
h with stirring (Fig. 1). The reaction was continuously -3', -5'), 6.68-6.67 (m, 2H, -3'', -5''), 4.84 (s, 6H,
monitored by TLC with a solvent system of CHCl3- OCH3-2, OCH3-4), 4.75 (s, 2H, -7), 2.50-2.43 (m, 4H,
MeOH, usually at the ratio of 9:1. The precipitated -2, -6), 2.14 (s, 1H, O -4), 1.99 (d, 4H, = 13.82
products were collected by filtration and thoroughly Hz, -3,
-5); EIMS m/z: 432 (M+-HBr, C22H24
δ
J
H
H
H
H
H
H
H
H
H
H
H
J
H
H
washed with acetone to remove traces of reactants. BrNO4), 271, 250, 236, 189, 165, 151, 129, 81, 57.
They were then dissolved and recrystallized with an
appropriate solvent or the mixture of solvents.
4-(4'-Bromo-phenyl)-4-hydroxy-1-[2-(3'',4''-di-
hydroxy-phenyl)-2-oxo-ethyl]-piperidinium
4-(4'-Bromo-phenyl)-4-hydroxy-1-[2-(2''-nitro-phe- bromide (PD6)
nyl)-2-oxo-ethyl]-piperidinium bromide (PD2)
Yield 65%, m.p. 262oC; IR
Yield 67%, m.p. 272oC; IR max (KBr) cm−1: 3373, 3188, 2931, 1678, 1583, 1323, 1274, 790, 542; UV
2916, 1743, 1587, 1380, 540; UV
max (MeOH) nm: 265, nm: 309, 280, 228; 1H-NMR (MeOD, 500 MHz):
259, 208, 196; H-NMR (d6-DMSO, 400 MHz): 8.41 7.44 (m, 6H, -2', -6', -3', -5', -2'', -6''), 6.86 (d,
(s, 2H, -3'', -6''), 7.57-7.55 (m, 2H, -4'', -5''), 7.40- 1H, = 8.06 Hz, -5), 4.85 (s, 2H, O -3'', O -4''), 4.36
7.38 (m, 4H, -2', -6', -3', -5'), 5.5 (s, 2H, -7), (s, 2H, -7), 2.34-2.27 (m, 4H, -2, -6), 2.14 (s, 1H,
3.37-3.17 (m, 4H, -2, -6), 2.09-2.06 (m, 1H, O -4), -4), 1.84 (d, 4H, = 13.97 HZ, -3, -5); EIMS m/
= 13.6 Hz,
ν
max (KBr) cm−1: 3303, 3076,
max (MeOH)
7.51-
ν
λ
λ
δ
1
δ
H
H
H
H
H
H
H
H
H
H
H
J
H
H
H
H
H
H
H
H
H
H
H
H
H
OH
J
H
H
1.76 (d, 4H,
J
H
-3,
H
-5); EIMS m/z: 419
z
: 406 (M+-HBr, C19H20 BrNO4), 271, 2679, 239, 189,
(M+-HBr, C19H19BrN2O4), 257, 255, 237, 210, 183, 158, 182, 136, 130, 84, 57.
129, 79, 57.
Analgesic activity
4-(4
nyl)-2-oxo-ethyl]-piperidinium bromide (PD3)
Yield 64%, m.p. 254oC; IR
2943, 1708, 1585, 1382, 540; UV
266, 199; 1H-NMR (d6-DMSO, 400 MHz):
-2'', -4''), 7.57 (d, 1H, = 1.85 Hz, -6''), 7.55-7.49 The distal end of the tail was immersed in water
-5''), 7.40 (d, 2H, = 1.69 Hz, -3',
-5'), 7.38 thermostatically maintained at 51 ± 1oC. (Withdrawal
= 1.88 Hz, -2', -6'), 5.52 (s, 2H, -7), 3.44- time of the tail from the hot water was measured in
-2, -6), 2.11-2.03 (m, 1H, O -4), 1.76 (d, seconds and the reaction time that was obtained from
= 13.3 Hz, -3,
-5); EIMS m/z: 419 (M+-HBr, three separate measurements). A cut-off time of 180
C19H19 BrN2O4), 272, 268, 239, 190, 183, 155, 130, 80, sec was used to prevent tissue damage. The mean of
'-Bromo-phenyl)-4-hydroxy-1-[2-(3''-nitro-phe-
The analgesic activity was determined by a tail-
immersion method in mice (Di Stasi et al., 1988). Mice
ν
max (KBr) cm−1: 3411, 3273, of either sex between 20-25 gm were divided into groups
λ
max (MeOH) nm: 301, of seven each. They were held in a suitable restrainer
δ
8.35 (s, 2H, from which the whole tail was extending outwards.
H
H
J
H
(m, 1H,
(d, 2H,
H
J
J
H
H
H
H
H
3.17 (m, 4H,
4H,
H
H
H
H
J
H
56, 57.
these measurements prior to drug administration was
the pre-drug tail flick latency. Three readings were
then taken at time intervals of +30, +60, +90, +120,
+150 and +180 min after administration of the com-
4-(4
nyl)-2-oxo-ethyl]-piperidinium bromide (PD4)
Yield 69%, m.p. 270oC; IR
2921, 1706, 1587, 1378, 540; UV
250, 219; 1H-NMR (d6-DMSO, 400 MHz):
-3'', -5''), 7.57 (d, 2H, = 2.51 Hz, -2'',
(d, 2H, = 2.48 Hz, -3', -5'), 7.40 (d, 2H,
Hz, -2', -6'), 5.52 (s, 2H, -7), 3.44-3.20 (m, 4H,
-6), 2.13-2.05 (m, 1H, O -4), 1.75 (d, 4H, = 13.51
-3,
-5); EIMS m/z: 419 (M+-HBr, C19H19 BrN2O4),
'-Bromo-phenyl)-4-hydroxy-1-[2-(4''-nitro-phe-
ν
max (KBr) cm−1: 3396, 3137, pounds. The mean of the three readings was the post
λ
max (MeOH) nm: 289, drug latency time. Tail flick latency difference (TFLD)
8.49 (s, 2H, was used to measure the analgesia produced by the
-6''), 7.54 standard and derivatives. TFLD was calculated as:
= 1.92
δ
H
H
J
H
H
J
H
H
J
Analgesic TFLD = Post-drug tail flick latency
Pre-drug tail flick latency
H
H
H
H-
−
2,
H
H
J
Hz,
H
H
Analgesic activity was expressed as TFLD ± S.E.M.
in seconds. Significant differences between means were
268, 257, 236, 208, 182, 158, 129, 81, 57.
determined by a student’s
t-test and values of
p < 0.05
were considered as significant while
p
< 0.01 was highly

Piperidine Derivatives for Pain and Platelet Aggregation
1955
significant.
gregation was induced by adding platelet activating
factor purchased from Sigma Chemical Company at a
concentration of 800 nM in PRP. The antiplatelet
Docking studies
Synthesized compounds were docked with opioid re- effects of 4-(4-bromophenyl-4-piperidinol (PD1) and
ceptor. For this study, a crystal structure of the opioid its derivatives (PD2-6) were studied by pretreatment
receptor (PDB ID: 3LWL) was used. Docking results of platelets for one min with these compounds fol-
were analyzed by Argus Lab software, 4.0.1. (DesJarlais lowed by addition of the platelet activating factor (800
et al., 1988). All water molecules and ligand atoms nM). The resulting aggregation was recorded for 5
were removed. Hydrogen atoms in the protein were min monitoring changes in light transmission as a
allowed to optimize. Molecular structures were drawn function of time and expressed as percent inhibition
using Marvin Sketch. Energy minimization was compared with control (platelet aggregating factor
performed by Argus Lab using Hartree-Fock method (PAF) = 800 nM). Acetylsalicylic acid, purchased from
(Jones et al., 1997).
Sigma Chemical Company, was used as the posi-
tive control for comparison. Differences between the
control and the compounds were analyzed by a student’s
Anti-platelet activity
Measurement of platelet aggregation
t-test (Zheng et al., 1995).
Blood was drawn by veinous puncture from healthy
humans (free of medications for one week). Blood
samples were mixed with 3.8% (w/v) sodium citrate
solution (9:1) and centrifuged at 260 g for 15 min at
20oC to obtain platelet rich plasma. All aggregation
RESULTS
Chemistry
All compounds, PD2 to PD6 were synthesized via a
studies were carried out at 37oC with PPP (platelet- simple one-step synthesis (Fig. 1). Phenacyl halides
rich plasma) with counts between 2.5 and 3.0
× , meta and para
108/ with various substitutions at ortho
mL of plasma. All experiments were performed within positions were reacted with 4-(4'-bromo-phenyl)-4-
3 h of preparation of PPP (Rasheed et al., 2004a, piperidinol. The modification was carried to assess the
2004b). Aggregation of platelets was monitored using effect of various substituents as potentiating targets
a Dual-channel Lumi-aggregometer (Model 400 Chrono- and to evaluate the structure activity relationships by
log Corporation) in 0.45 mL aliquots of PPP. PPP (0.55 conducting analgesic and antiplatelet assays. Com-
mL) was taken as blank source. An aggregometer qu- pounds PD2
,
PD3 and PD4 contained a nitro group
meta and para position of the phenyl
antified the aggregation by measuring and comparing at the ortho
,
light transmission through PPP and PRP was used as ring, respectively. Compound PD5 contains two
a platelet source to determine antiplatelet effect where methoxy groups at the ortho and para positions, while
as PPP was used as a blank source in the aggregometer. PD6 contains two hydroxyl groups at the ortho and
The PRP containing cuvette was continually stirred at meta positions of phenyl ring.
37oC. The final volume was made up to 0.5 mL with
the test drug dissolved in appropriate vehicle known
to be devoid of any effect on platelet aggregation. Ag-
Analgesic activity
The results showed that the parent compound PD1
,
Fig. 1. Synthesis of compounds PD2 through PD6
.

1956
Z. S. Saify et al.
Table I. Analgesic effects of 4-(4-Bromophenyl)-4-piperidinol (PD1) and its phenacyl derivatives PD2-PD6 in mice using
a tail immersion assay
Analgesia TFLD (mean increase in latency after drug administration ± S.E.M.)
Dose
(mg/kg)
Compound
30 min
60 min
90 min
120 min
150 min
180 min
Control
(negative control)
−
1.5 ± 0.02
1.9 ± 0.01
1.3 ± 0.01
1.8 ± 0.03
1.5 ± 0.05
1.2 ± 0.05
PD-1
PD-2
PD-3
PD-4
PD-5
PD-6
50
50
50
50
50
50
50
25** ± 0.46
0.036 ± 0.15
7.4** ± 1.15
2.31 ± 0.57
4.73** ± 0.95 5.67** ± 1.11 2.26* ± 0.45
2.38 ± 1.80 2.28 ± 0.94 2.52* ± 0.56
27** ± 0.35
0.08 ± 0.11
9.8** ± 2.20
50** ± 0.30
0.12 ± 0.05
9.7** ± 2.40
48** ± 0.95
0.18 ± 0.06
4.1* ± 0.99
1.62 ± 0.39
0.69 ± 0.30
2.21 ± 0.66
35** ± 0.55
0.04 ± 0.15 0.361 ± 0.04
0.22 ± 1.25
1.52 ± 0.17
0.39 ± 0.32
0.15 ± 0.23
30** ± 0.54
0.10 ± 0.29
1.51 ± 0.50
0.48 ± 0.13
0.84 ± 0.73
2.79 ± 1.10 3.22* ± 0.70
Pethidine HCl
2.26* ± 0.07 3.52** ± 0.09 2.82** ± 0.18 2.57** ± 0.20 1.92** ± 0.23 1.57* ± 0.27
((positive control)
Treatment: Intraperitoneal (i.p); 7 animals/group. Significant differences determined by a student
0.01 as compared to control. Control: Animals treated with vehicle (water for injection).
t-test: *p < 0.05, **p <
Fig. 2. Analgesic effect of compounds PD1 to PD6 and Pethidine HCl (standard) in the tail immersion assay in mice.
Control = Animals treated with vehicles (water for injection). n = 7 animals/group. Significant differences were determined
by a student’s t-test: *p < 0.05, **p < 0.01.
4-(4-bromophenyl)-4-piperidinol exhibited a highly sig- whereas compound PD6 was the least active. The SAR
nificant analgesic effect at a dose of 50 mg/kg of body study revealed that among all the nitrophenacyl deri-
weight (Table I, Fig. 2). All the phenacyl derivatives of vatives, a nitro group at meta position, i.e. compound
compound PD1 with different substitutions at the PD3 exhibited marked analgesic activity while PD2
phenyl ring were active in reducing pain except com- and PD4 with nitro groups at ortho and para positions,
pound PD2. Compound PD3, 4-(4'-bromo-phenyl)-4- respectively did not exhibit any analgesic activity.
hydroxy-1-[2-(3''-nitro-phenyl)-2-oxo-ethyl]-piperidinium
bromide with a nitro group at meta position showed
Docking studies
highly significant activity and was found to be the
The top binding poses of the compounds were model-
most active one (Fig. 2). Compound PD5, 4-(4'-bromo- ed into the active site of opioid receptor to examine
phenyl)-4-hydroxy-1-[2-(2'',4''-dimethoxy-phenyl)-2-oxo- their interaction with protein residues. The analysis
ethyl]-piperidinium bromide showed highly significant of docking predictions showed that compound PD3
activity soon after 30 min that was persisted for 1 h, and PD5 docked to the receptor with minimum docking

Piperidine Derivatives for Pain and Platelet Aggregation
1957
Fig. 4. Effect of synthesized compounds on PAF-induced
human platelet aggregation. (
idinol (PD1). ( ) 4-(4’-Bromo-phenyl)-4-hydroxy-1-[2-(3’’-ni-
trophenyl)-2-oxo-ethyl]-piperidinium-bromide (PD3). ( ) 4-
(4’-Bromo-phenyl)-4-hydroxy-1-[2-(2’’,4”-dimethoxy-phenyl)-
A) 4-(4-Bromophenyl)-4-piper-
B
C
2-oxo-ethyl]-piperidinium bromide (PD5). (D) Aspirin. Con-
trol = PAF 800 nM.
Fig. 3. Docking of PD3 in the active site of the opioid
receptor.
the amino group of ARG 573, indicating a distance of
energy. The activity of compound PD3 may be attri- 1.2563 Å (Fig. 3). This binding site is significant in
buted to the interaction of O2 of the nitro group with case of compound PD3 only, whereas for the other
compounds, such a fit was not suitable with regard to
the respective amino acids.
Table II. The effect of 4-(4–Bromophenyl)-4- piperidinol
(PD1) and its derivatives PD2-PD6 on in vitro human
platelet aggregation induced by platelet activating factor
(800 nM).
Anti-platelet activity
The treatment of platelet-rich plasma with PAF
(800 nM) produced marked aggregation of platelets.
The platelets were then pre-incubated with the parent
compound PD1 and its derivatives followed by the
addition of PAF (800 nM) to determine their anti-
platelet effect. The results showed that the parent
compound failed to inhibit aggregation of platelets up
to 200 mM (Fig. 4A). Platelets were then treated with
compound PD3 and with PD5 individually for 1 min
at different concentrations followed by addition of
PAF and it was found that both the compounds inhi-
bited PAF-induced platelet aggregation at IC50 = 80
and 0.06 mM (Fig. 4B, C), respectively. The antiplatelet
effects of these compounds were comparable with the
PAF receptor antagonist aspirin (acetyl salicylic acid)
IC50 mM
Compounds
± S.E.M.
4-(4–Bromophenyl)-4- piperidinol (PD1)
4-(4’–Bromo-phenyl)-4-hydroxy-1-
[2-(2’’-nitro-phenyl)-2-oxo-ethyl]
- piperidinium bromide (PD2)
4-(4’–Bromo-phenyl)-4-hydroxy-1-
[2-(3’’-nitro-phenyl)-2-oxo-ethyl]
- piperidinium bromide (PD3)
4-(4’–Bromo-phenyl)-4-hydroxy-1-
[2-(4’’-nitro-phenyl)-2-oxo-ethyl]
- piperidinium bromide (PD4)
4-(4’–Bromo-phenyl)-4-hydroxy-1-
[2-(2’’,4”-dimethoxy phenyl)-2-oxo-ethyl]
- piperidinium bromide (PD5)
4-(4’–Bromo-phenyl)-4-hydroxy-1-
[2-(3’’,4”-dihydroxy phenyl)-2-oxo-ethyl]
- piperidinium bromide (PD6)
WEB 2086
NE
NE
80 ± 3.4
NE
0.06 ± 0.001
NE
IC50 = 150 µM (Fig. 4D). The other derivatives PD2,
PD4 and PD6 were found inactive in inhibiting
platelet aggregation.
DISCUSSION
5 ± 0.3*
Acetyl salicylic acid
150 ± 3.4*
Interesting and encouraging results obtained when
parent compound 4-(4-bromophenyl)-4-piperidinol, PD1
and its meta nitro phenacyl derivative, PD3 were
Data indicate half-maximal inhibitory effect (IC50) of vari-
ous agents. IC50 = concentration (mM) producing 50% in-
hibition of aggregation. NE: no effect. *concentration in µM.

1958
Z. S. Saify et al.
Mehta, P. P., Munie, G. E., and Swearingen, C. A., Sy-
nthesis and structure-activity relationships of beta- and
alpha-piperidine sulfone hydroxamic acid matrix metallo-
proteinase inhibitors with oral antitumor efficacy. J. Med.
Chem., 48, 6713-6730 (2005).
DesJarlais, R. L., Sheridan, R. P., Seibel, G. L., Dixon, J. S.,
Kuntz, I. D., and Venkataraghavan, R., Docking: successes
and challenges. J. Med. Chem., 31, 722-729 (1988).
Di Stasi, L. C., Costa, M., Mendaçolli, S. L., Kirizawa, M.,
Gomes, C., and Trolin, G., Screening in mice of some
medicinal plants used for analgesic purposes in the state
of São Paulo. J. Ethnopharmacol., 24, 205-211 (1988).
Erol, D. D. and Demirdamar, R., Analgesic and anti-inflam-
matory activity screening of 6-acyl-3-piperidinomethyl-
2(3H)-benzoxazolone derivatives. Farmaco, 49, 663-666
(1994).
Feng, Z., Gollamudi, R., Dillingham, E. O., Bond, S. E., Lyman,
B. A., Purcell, W. P., Hill, R. J., and Korfmacher, W. A.,
Molecular determinants of the platelet aggregation inhi-
bitory activity of carbamoylpiperidines. J. Med. Chem.,
35, 2952-2958 (1992).
Guo, Z., Zheng, X., Thompson, W., Dugdale, M., and Gollamudi,
R., New carbamoylpiperidines as human platelet aggrega-
tion inhibitors. Bioorg. Med. Chem., 8, 1041-1058 (2000).
Imamura, S., Nishikawa, Y., Ichikawa, T., Hattori, T.,
Matsushita, Y., Hashiguchi, S., Kanzaki, N., Iizawa, Y.,
Baba, M., and Sugihara, Y., CCR5 antagonists as anti-
HIV-1 agents. Part 3. Synthesis and biological evaluation
of piperidine-4-carboxamide derivatives. Bioorg. Med.
Chem., 13, 397-416 (2005).
Jones, G., Willett, P., Glen, R. C., Leach, A. R., and Taylor,
R., Development and validation of a genetic algorithm for
flexible. J. Mol. Biol., 267, 727-748 (1997).
Kordik, C. P., Luo, C., Gutherman, M., Vaidya, A. H.,
Rosenthal, D. I., Crooke, J. J., McKenney, S. L., Plata-
Salaman, C. R., and Reitz, A. B., Diarylacetylene piperidinyl
amides as novel anxiolytics. Bioorg. Med. Chem. Lett., 16,
3065-3067 (2006).
Köksal, M. and Bilge, S. S., Synthesis and antidepressant-
like profile of novel 1-aryl-3-[(4-benzyl) piperidine-1-yl]
propane derivatives. Arch. Pharm. (Weinheim), 340, 299-
303 (2007).
Lawrence, W. P., Howell, R. D., and Gollamudi, R., Anti-
platelet activity of nipecotamides in experimental throm-
evaluated for analgesic activity as these compounds
produced highly significant antinociceptive effects
throughout the experiment.
Platelets play an important role in acute inflamma-
tion. They accumulate and respond to injury by releas-
ing important mediators such as 5-hydroxytryptamine
(5-HT), prostaglandins (PGs) and PAF which contribute
to the inflammatory process. Further Thromboxane A2
(TXA2) formed by platelets have been reported to be a
potent constrictor of blood vessels and an aggregator
of platelets. TXA2 is involved in the pathogenesis of
circulatory shock and cardiac ischaemia associated
with arrythmias (Montrucchio et al., 2000). Human
platelets show affinity binding sites for PAF.
The SAR studies showed that the anti-platelet effect
was due to the presence of a nitro substitution at the
meta position in the phenyl ring. It was concluded
that compounds possessing meta nitrophenyl and
dimethoxy groups in the phenyl ring at ortho and para
positions (e.g. PD5) showed potential for antiplatelet
effects (Table II). The underlying mechanism of their
antiplatelet action is due to their interaction with the
phospholipids of the platelet membrane, thus stabilizing
it against agonist-induced aggregation.
The analgesic and antiplatelet activity of two deri-
vatives of 4-(4-bromophenyl)-4-piperidinol, namely PD3
and PD5, might be due to their PAF receptor antag-
onistic effect which leads to inhibition of the second
messengers IP3, DAG and calcium signaling pathways.
It was observed that compound PD3, 4-(4'-bromo-
phenyl)-4-hydroxy-1-[2-(3''-nitro-phenyl)-2-oxo-ethyl]-
piperidinium bromide, with nitro group at the meta
position was the most active as an analgesic and PD5
,
with an IC50 = 0.06 mM, was the most active compound
against PAF-induced aggregation. Further studies are
required to determine their PAF receptor binding
affinity and effects in COX pathways so as to pursue
their downstream signaling mechanism.
ACKNOWLEDGEMENTS
We thank Higher Education Commission Islamabad
for the financial support of this study. The Institute of
Pharmaceutical Sciences, Riphah International Uni-
versity Islamabad, Pakistan, is highly appreciated for
providing facilities to conduct the antiplatelet studies.
bosis in mice. J. Pharm. Sci., 83, 222-225 (1994)
.
Miguel, O. G., Santos, A. R., Calixto, J. B., Delle Monache, F.,
and Yunes, R. A., Antinociceptive activity of the natural
piperidine alkaloid hydrochlorides from Syphocampylus
verticellatus. Z. Naturforsch. C, 57, 81-84 (2002).
Montrucchio, G., Alloattig, G., and Camussi, G., Role of plate-
let-activating factor in cardiovascular pathophysiology.
Physiol. Rev., 1669-1699 (2000).
Mushtaq, N., Saify, Z. S., Akhtar, S., Arif, M., Haider, S.,
and Saba, N., Synthesis of some novel analogues of 4-(1-
pyrrolidinyl) Perpridine and their effects on plasma
glucose level. Pak. J. Phar. Sci., 23, 220-223 (2010).
REFERENCES
Becker, D. P., Villamil, C. I., Barta, T. E., Bedell, L. J.,
Boehm, T. L., Decrescenzo, G. A., Freskos, J. N., Getman,
D. P., Hockerman, S., Heintz, R., Howard, S. C., Li, M. H.,
McDonald, J. J., Carron, C. P., Funckes-Shippy, C. L.,

Piperidine Derivatives for Pain and Platelet Aggregation
1959
Ramachandran, R., Rani, M., Senthan, S., Jeong, Y. T., and
Kabilan, S., Biological activity of piperidine derivatives.
Eur. J. Med. Chem., 46, 1926-1934 (2011).
Rasheed, H., Tirmizi, A. H., Salahuddin, F., Rizvi, N. B.,
Arshad, F., Farooq, S. Z., and Saeed, S. A., Calcium sig-
naling in human platelet aggregation mediated by platelet
activating factor and calcium ionophore, A23187. J. Biol.
Sci., 4, 117-121 (2004a).
Rasheed, H. and Saeed, S. A., Involvement of thromboxane
A2 and tyrosine kinase in the synergistic interaction of
platelet activating factor and calcium ionophore A23187
in human platelet aggregation. Exp. Mol. Med., 36, 220-
225 (2004b).
Saeed, M., Saify, Z. S., Gilani, A. H., Haider, M. S., and
Iqbal, Z., Studies on the effects of piperidine derivatives
on blood pressure and smooth muscles contractions. Arch.
Pharm. Res., 21, 370-373 (1998).
Saify, Z. S., Nisa, M., Azhr, K. F., Azim, M. K., Rasheed, H.,
Mushtaq, N., Arain, M. A., Haider, S., Khanum, M., and
Ahmed, W., Characterization of plasmodium falciparum
aspartic protease inhibition by piperidine derivatives.
Nat. Prod. Res., 25, 1965-1968 (2011).
Thaler, F., Varasi, M., Carenzi, G., Colombo, A., Abate, A.,
Bigogno, C., Boggio, R., Carrara, S., Cataudella, R. D. F.,
Reali, V., Vultaggio, S., Dondio, G., Gagliardi, S., and
Mercurio, C., Spiro [chromane-2,4'-piperidine]-based histone
deacetylase inhibitors with improved in vivo activity.
Chem. Med. Chem., 7, 709-21 (2012).
Zheng, X., Salgia, S. R., Thompson, W. B., Dillingham, E. O.,
Bond, S. E., Feng, Z., Prasad, K. R., and Gollamudi, R.,
Design and synthesis of piperidine-3-carboxamides as
human platelet aggregation inhibitors. J. Med. Chem., 38,
180-188 (1995).