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PHARMACOLOGICAL EVALUATION OF PACHYRRHIZUS
EROSUS (L) SEEDS FOR CENTRAL NERVOUS SYSTEM
DEPRESSANT ACTIVITY
MOHD ABID, H. J. HRISHIKESHAVAN AND MOHAMMED ASAD*
Krupanidhi College of Pharmacy,
#5, Sarjapur Road, Koramangala,
Bangalore – 560 034
( Received on July 1, 2005 )
Abstract : The research work deals with the screening of ethanol and
chloroform extracts of Pachyrrhizus erosus seeds for central nervous
system (CNS) depressant activity. The Pachyrrhizus erosus seed is known
to contain rotinoids, flavonoids and phenylfuranocoumarin derivatives as
chemical components and is reported to have antifungal, antisecretory,
insecticides, antibacterial and spasmolytic activity. Since seeds of
Pachyrrhizus erosus is used as folk medicine in treatment of insomnia,
we made an attempt to study its CNS depressant effect. The different
activities studied were potentiation of pentobarbitone-induced sleep, test
for locomotor activity, effect on muscle co-ordination, antiaggressive and
antianxiety activities. The result of the study reflected that ethanol extract
of the seeds (150 mg/kg, p.o) decreased locomotor activity, produced muscle
relaxation and showed antianxiety and antiaggressive activity.
Key words : Pachyrrhizus erosus sedative muscle relaxant
antianxiety antiaggressive
Indian J Physiol Pharmacol 2006; 50 (2) : 143–151
*Corresponding Author : e-mail : mohammedasad@rediffmail.com
INTRODUCTION
Advance in science and technology has
contributed to an enormous improvement in
the quality of life of humankind. However,
modern life stress, associated trials and
tribulation are responsible for the surge
in incidence of variety of psychiatric
disorders. Path breaking research in
psychopharmacology has flooded the market
place with drugs for specification. For
instance, benzodiazepines (diazepam,
nitrazipam lorazepam and alprazolam etc)
are the most frequently prescribed synthetic
drugs for variety of condition particularly
anxiety, depression, epilepsy and insomnia.
But these psychoneural drugs have very
serious side effects like chronic use of
benzodiazepines causes deterioration of
cognitive function, physical dependence and
tolerance. Besides addiction liabilities,
benzodiazepines adversely affect the
respiratory, digestive and immune system
of body and the chronic treatment with
benzodiazepines often prove more harmful
in the longer run (1).
In this context, a resurgence of interest
144 Abid et al Indian J Physiol Pharmacol 2006; 50(2)
in medicine from natural sources (mainly
plant products) is seen and there is
tremendous hope that drugs of plant origin
will have significantly lesser side effects
than that observed with synthetic drugs
while having comparable efficacy.
A variety of naturally occurring
drugs such as Thymus linearis, Lactuca
seroila, Papaver somniferum (opium) and
Atropa belladonna were tested for
psychopharmacological effects and were
found to be effective in the treatment of
psychiatric disorders (2). The plant
Pachyrrhizus erosus (L) is a tuberous root
(Leguminasae), cultivated in South East Asia
including India. Seeds of Pachyrrhizus
erosus contain rotinoids, isoflavonoids and
phenylcoumarine, which are reported to
possess potent activity against anti-Herps
Simplex Virus type 1 and type II (3). Seeds
of this plant were found to possess
antibacterial activity against Helicobacter
pylori (4). Tuberous root of Yam bean
(Pachyrrhizns erosus) contains two major
proteins named as YBG1 and YBG2 that
were found to exhibit cysteine proteolytic
activity (5). Further, seed extract of this
plant is used as pesticide, anti-oxidant, anti-
inflammatory, anti-fungal, anti-secretory,
insecticide and spasmolytic (6).
Pachyrrhizuss erosus (L) is used as folk
medicine in treatment of insomnia, although
it is not reported in literature. Some of the
plants like Montonoa tomentosa, Kunth,
Castillega tenuiflora and Penstemen
barbatus and Byrsonima containing chemical
constituents like coumarin, flavonoids,
monoterpines, rotinoids, proanthocyanidine
and glycolipids were reported to possess CNS
depressant activity (6). Based on the above
information, we thought it is worthwhile to
evaluate the Pachyirrhizus erosus (L) seeds
for CNS depressant activity.
METHODS
Experimental animals
Swiss albino mice of either sex weighing
between 12–35 g were used in the present
study. The experimental protocol was
approved by the Institutional Animal Ethics
Committee. The animals were maintained
under standard conditions in Committee for
the Purpose of Control and Supervision on
Experiments on Animals (CPCSEA)
approved Institutional Animal House.
Chemicals
Pentobarbitone sodium was obtained
from Sigma-Aldrich, USA, Diazepam was
procured from Cipla, Ahmedabad (India),
Chloroform was purchased from Nice
chemicals, Cochin (India), Chlorpromazine
from Sun Pharma, Mumbai (India).
Diethyl ether from Merck Limited,
Ahmedabad (India) and petroleum ether was
obtained from S.D. Fine Chemicals, Mumbai
(India).
Extraction of Pachyrrhizus erosus seeds
The Pachyrrhizus erosus seeds were
collected from Kolkata (West Bengal, India),
in winter season. They were dried, powdered
and subjected to extraction by Soxhlet
method using chloroform and ethyl alcohol
as solvents. Extractions of dried coarse
powder of Pachyrrhizus erosus seeds were
Indian J Physiol Pharmacol 2006; 50(2) Pharmacological Evaluation of Pachyrrhizus Erosus 145
done in a manner, initially with petroleum
ether, chloroform, and then with ethyl
alcohol. Evaporation of solvents from the
extract was done using rotary vacuum
evaporator. A sticky mass was obtained after
evaporation of solvent. The extracts were
subjected to qualitative phytochemical
analysis. A suspension of the extracts was
prepared using 2% w/v Tween 80 in distilled
water.
Acute oral toxicity study
The acute oral toxicity study was
performed according to the OPPTS (Office
of Prevention, Pesticides and Toxic
Substance) guidelines following Up and
Down procedure (7).
Selection of the extract
The chloroform and ethanol extract of
Pachyrrhizus erosus seeds were evaluated
for sedative-hypnotic activity in
pentobarbitone induced sleep test. The
extract, which potentiated the sedative-
hypnotic activity of pentobarbitone was
chosen for further study (8).
Test for locomotor activity
The spontaneous locomotor activity of
each mouse was recorded individually for 10
min using actophotometer. The ethanolic
extract of Pachyrrhizus erosus seeds
(EEPES) was administered at two doses of
EEPES (75 and 150 mg/kg, p.o) 60 min
before the test and chlorpromazine (3 mg/kg,
i.p), used as standard was given 30 min
before the test. The control group was
treated with 2% w/v Tween 80 orally, 60 min
before test (9).
Muscle co-ordination test
This test was carried out using inclined
plane and rotarod apparatus.
1. Inclined plane :
The plane consists of two rectangular
plywood boards connected at one end by a
hinge. One board is the base; the other is
the movable inclined plane. Two plywood
side panels with degrees marked on their
surface are fixed on the base. A rubber mat
with ridges 0.2 cm in height is fixed to the
inclined plane, which was set at 65 degrees.
Swiss albino mice were taken and divided
into four groups, each group comprised of 6
animals. The two doses of EEPES (75 and
150 mg/kg) were administered orally, the
standard group was treated with diazepam
(4 mg/kg) intraperitonially and control group
received Tween 80 (2% w/v) orally. The test
was carried out 30, 60 and 90 min after
administration of drugs and vehicle. The
animals were placed at the upper part of
the inclined plane and were given 30 sec to
hang on or to fall off (10).
2. Rotarod
The rotarod apparatus consists of a metal
rod (3 cm diameter) coated with rubber
attached to a motor with the speed adjusted
to 2 rotations per minute. The rod is 75 cm
in length and is divided into 6 sections by
metallic discs, allowing the simultaneous
testing of 6 mice. The rod is in a height of
about 50 cm above the tabletop in order to
discourage the animals from jumping off the
roller. Cages below the section serve to
restrict the movements of the animals when
they fall from the roller.
146 Abid et al Indian J Physiol Pharmacol 2006; 50(2)
Swiss albino mice underwent a pretest on
the apparatus. Only those animals, which
had demonstrated their ability to remain on
the revolving rod (20 rpm) for 5 min, were
used for the test. The animals were treated
in the same way as mentioned under inclined
plane test (11).
Anti-anxiety activity
The anti-anxiety activity was evaluated
using staircase test and elevated plus maize
test.
1. Staircase test
Staircase consists of five identical steps
2.5 cm high, 10 cm wide and 7.5 cm deep.
The internal height of the walls is constant
along whole length of the staircase. The
drugs and treatments were same as
mentioned under inclined plane. The animals
were placed on the floor of the box with its
back to the staircase. The number of steps
climbed and the number of rears were
counted over a 3 min period. A step was
considered to be climbed only if the mouse
had placed all four paws on the step. In
order to simplify the observation, the
numbers of steps descended were not taken
into account. After each step the box was
cleaned in order to eliminate any olfactory
cues, which might modify the behavior of
the next animal (12).
2. Elevated plus maze
The apparatus consist of two open arms
(5 × 10 cm) and two closed arms (5 × 10 × l5
cm) radiating from a platform (5 × 5 cm) to
form a plus-sign figure. The apparatus was
situated 40 cm above the floor. The open-
arms edges were 0.5 cm in height to keep
the mice from falling and the closed-arms
edges were 15 cm in height. The drugs and
treatments were same as mentioned under
inclined plane.
The animal was placed at the center of
the maze, facing one of the closed arms.
During 5 min test period the following
measures are taken :
• The number of entries into open arms
• The number of entries into closed arms
• Time spent in the open arms
Arm entry was counted when the animal
had placed all of its four paws on it. The
procedure was conducted in a sound
attenuated room, with observations made
from an adjacent room (14).
Anti-aggressive activity
This was carried out using isolation
induced aggression test. Male albino mice
weighing about 12–20 gm are kept isolated
in small cages for a period of 6 weeks. Prior
to the administration of the drag, the
aggressive behavior of the animals was
tested. The male mouse being accustomed
to live together with other animals was
placed into the cage of an isolated mouse.
The aggressive behavior of the isolated
mouse was recorded. The following
parameters were used to assess aggressive
behavior
Indian J Physiol Pharmacol 2006; 50(2) Pharmacological Evaluation of Pachyrrhizus Erosus 147
• Hitting the tail on the bottom of the cage
• Screaming (piercing noise) and
• Biting.
After these initial tests, the animals were
subjected to different drug treatments as
mentioned under inclined plane. The
aggressiveness was studied again after
60 and 120 min after drug or vehicle
administration (15).
Statistical analysis
Results were expressed as Mean±SEM
The differences between experimental
groups were compared using one-way
Analysis of Variance (ANOVA) followed by
Dunnett’s test and were considered
statistically significant when P<0.05.
RESULTS
The preliminary phytochemical investigation
of the EEPES revealed the presence of amino
acids and flavones.
In acute oral toxicity study, EEPES
produced death at doses of 2000 and 1000
mg/kg while with chloroform extract, there
was death at doses of 2000, 1000, 750, 650,
450, 175 mg/kg, but it was safe at a dose of
75 mg/kg. EEPES was safe at a dose of 750
mg/kg orally. Hence 1/5th and 1/10th of this
dose i.e. 7.5 mg/kg and 15 mg/kg of
chloroform extract and 75 mg/kg and 150
mg/kg of EEPES were used for the study.
Pentobarbitone induced sleeping time
The EEPES (75 mg/kg p.o) significantly
increased the pentobarbitone induced
sleeping time (P<0.001). The increase in
duration of action was 1075%. No significant
effect was observed with the chloroform
extract (Table I).
TABLE I : Effect of EEPES in pentobarbitone-induced
sleep.
Pentobarbitone
(40 mg/kg, i.p) Onset of Duration Percentage
30 min Post action of action Sleeping
treatment of (Min) (Min) time
the vehicle
and drugs
Control 5.66±0.49 132.66±0.16 100
(Vehicle 6 ml/
kg, p.o)
Chloroform extract 5.83±0.16 118±14.00 89
(7.5 mg/kg, p.o)
Ethanolic extract 6.00±0.25 1420.66±0.21*** 1075
(75 mg/kg, p.o)
All values are Mean±SEM, ***P<0.001 when compared
with control.
Test for locomotor activity
High dose of EEPES (150 mg/kg p.o) and
diazepam (4 mg/kg i.p) decreased the
locomotor activity significantly (P<0.01)
whereas, low dose of EEPES (75 mg/kg p.o)
did not show a significant reduction in the
locomotor activity (Table II).
Test for muscle coordination
1. Inclined lane
The number of animals falling from
inclined plane after 60 and 90 min of
treatment were significantly more in
diazepam (4 mg/kg i.p) treated and EEPES
(150 mg/kg p.o) treated groups when
compared to control group (P<0.01). Low
148 Abid et al Indian J Physiol Pharmacol 2006; 50(2)
dose of test drug was ineffective. (Table II).
2. Rotorod test
This test, EEPES (150 mg/kg)
significantly reduced the time spent by the
animals on revolving rod when compared to
control (P<0.05). The standard drug
(diazepam) also showed significant effect
when compared to control (P<0.01) Low dose
of drug (75 mg/kg) did not show any
significant effect (Table II).
Anti-anxiety activity
1. Staircase test
The statistical summary of the rearing
and number of steps climbed is presented in
Table III. After 60 and 90 min of treatment,
a reduction in anxiety-linked behavior was
indicated by a reduction in number of
rearing and sedation that was evaluated by
number of steps climbed. High dose of
EEPES (150 mg/kg, p.o) and standard drug
(diazepam 4 mg/kg, i.p) significantly reduced
the number of rearing as well as the number
of steps climbed (P<0.01). Low dose of
EEPES (75 mg/kg, p.o) did not produce a
significant decrease in the number of rearing
or the number of steps climbed.
2. Elevated plus maze :
High dose of EEPES (150 mg/kg p.o),
significantly increased the time spent in
open arms (P<0.05) and number of entries
into closed arms (P<0.01) but did not affect
significantly the number of entries into open
arms when compared with control. The
standard drug (diazepam 4 mg/kg, i.p)
showed a significant decrease in the number
of entries into closed arms (P<0.01) and open
arms (P<0.05) and also significantly
increased the time spent in open arms
(P<0.01). Low dose of EEPES (75 mg/kg, p.o)
did not show any differences in activity
compared to control (Table III).
Anti-aggressive activity
Both EEPES (150 mg/kg p.o) and
diazepam (4 mg/kg i.p) produced marked
inhibition of aggressiveness in isolated mice
TABLE II : Effect of EEPES on locomotor activity in actophotometer and
muscle coordination in inclined plane and rotated apparatus.
No of animal falling down within (30 sec) from inclined plane Time spent on
revolving rod
Groups Actophotometer 30 min after 60 min after 90 min after in rotarod
score in 10 min administrations administrations administrations apparatus (sec)
Control 310.66±11.54 0±0 0±0 0±0 323.00±24.85
(Vehicle 6 ml/kg, p.o)
Ethanolic extract 268.33±10.27 0±0 0±0 0.16±0.16 298.00±32.47
(75 mg/kg, p.o)
Ethanolic extract 161.83±18.06** 0±0 0.66±0.21** 0.5±0.22** 199.5±41.59*
(150 mg/kg, p.o)
Standard drug 142.16±15.00** 0.66±0.21** 0.83±0.16** 0.83±0.166** 106.6±2.81**
All values are Mean±SEM, n=6, *P<0.05, **P<0.01 when compared with control.
Indian J Physiol Pharmacol 2006; 50(2) Pharmacological Evaluation of Pachyrrhizus Erosus 149
as indicated by a significant decrease in
screaming, hitting the tail on the bottom,
and biting. Low dose did not show any
significant effect (Table IV).
DISCUSSION
The study showed that EEPES (150 mg/
kg, p.o) possess sedative, antianxiety, muscle
relaxant and antiaggressive activity.
EEPES potentiated the sleep induced by
pentobarbitone suggesting that it possess
some sleep inducing property. The study on
the spontaneous motor activity showed that
EEPES (150 mg/kg, p.o) decreased the
frequency and the amplitude of movements.
The reduction of the spontaneous motor
activity could be attributed to the sedative
effect of the extract (12).
Inclined plane method was originally
developed for testing curare-like agents.
TABLE III : Effect of EEPES and diazepam in stair case test and elevated plus-maze test.
Elevated plus maze test
Stair case test
Groups No. of entry into
No. of climbing No. of rearing Time spent in
in 3 min in 3 min Closed arms Open arms open arms
Control 20.16±1.38 9.83±0.60 13.33±1.11 9.66±1.3 91.5±7.50
(Vehicle 6 ml/kg, p.o)
Ethanolic extract 13.66±0.80 8.16±0.47 9.83±1.35 6.66±0.80 107.16±10.89
(75 mg/kg, p.o)
Ethanolic extract 8.16±0.60** 6.00±0.57** 7.66±1.20** 6.83±1.66 147.33±9.97*
(150 mg/kg, p.o)
Diazepam 6.00±0.68** 5.1±0.60** 7.16±0.95** 4.83±1.35* 199.51±15.84**
(4 mg/kg, p.o)
All values are Mean±SEM, n=6, *P<0.05, **P<0.01 when compared with control.
TABLE IV : Effect of EEPES and diazepam on isolation induced aggression.
No. of Hitting the
Screaming Tail on the bottom Biting
Groups After After After After After After
60 min 120 min 60 min 120 min 60 min 120 min
Control 1.83±0.30 1.52±0.15 8.83±0.74 7.82±0.44 4.16±0.54 3.01±0.32
(Vehicle 6 ml/kg, p.o)
Ethanolic extract 1.16±0.47 0.96±0.47 7.33±1.05 7.33±1.05 3.16±0.87 2.06±1.01
(75 mg/kg, p.o)
Ethanolic extract 0.50±0.22* 0.82±0.28* 1.00±0.25** 2.37 ±0.42* 0.66±0.21** 0.66±0.33**
(150 mg/kg, p.o)
Diazepam 0.16±0.16** 0.18±2.91** 0.33±0.21** 0.16 ±0.03** 0.33±0.21** 0.12±0.09**
(4 mg/kg, p.o)
All values are Mean±SEM, n=6, *P<0.05, **P<0.01 when compared with control at the same time interval.
150 Abid et al Indian J Physiol Pharmacol 2006; 50(2)
Later on, it has been used by many authors
for testing compounds for muscle relaxing
activity of both centrally acting and
peripheral acting muscle relaxants (11).
EEPES (150 mg/kg, p.o) made the animals
unable to stay on inclined plane during
30 sec period. EEPES (150 mg/kg, p.o)
also reduced the time spent on the revolving
rod by mice in the rotarod test, a test
mainly used to screen centrally acting
muscle relaxants (12). This represented that
EEPES may have muscle relaxant activity,
which could be due to CNS depressant
activity.
The mouse staircase was used for the
assessment of anxiety (number of rearing)
and sedation (number of steps ascended).
Greater number of rear indicates anxiety
like behavior and lesser number of steps
ascended indicated increased sedation (13).
The present investigation successfully
detected the anxiolytic-like effects of EEPES
and diazepam; both significantly decreased
the number of rearing and number of steps
ascended compared to control. This showed
that EEPES has both anxiolytic and sedative
properties.
The sedative, muscle relaxant and
anxiolytic effects of EEPES could be due to
the interaction of isoflavonoids (chemical
constituent of the plant) with the GABA/
benzodiazepine receptor complex in brain
(16).
Elevated plus-maze test is used to
evaluate psychomotor performance and
emotional aspects of rodents (17). The
results showed that EEPES significantly
increased the time spent on the open arms
and decreased the number of entries into
open and closed arms. This type of effect is
observed with the drugs that act on GABA/
benzodiazepine receptor complex as well
with drugs that stimulate glucocorticoid
production and release in the adrenal
cortex (14), after administration of 5-HT1B
receptor antagonists and 5-HT1A agonists
(18). Therefore, with the present data,
it is difficult to predict the precise
mechanism for the anxiolytic activity of the
Pachyrrhizus erosus seeds.
EEPES showed inhibition of aggressiveness
in isolated mice. The serotoninergic system
is implicated in aggressive states and it has
been hypothesized that decreasing
serotoninergic activity may encourage
aggressive behavior (19). Since, both
antianxiety and antiaggressive effects are
seen with 5HT1A antagonists, it is assumed
that EEPES may also interact with the 5-
HT1A receptors.
To conclude, the ethanolic extract of
seeds of Pachyrrhizus erosus possess
sedative, anti-anxiety, muscle relaxant and
anti-aggressive properties. The result of the
present study substantiates the traditional
use of seeds of Pachyrrhizus erosus for the
treatment of insomnia.
ACKNOWLEDGEMENTS
The authors are thankful to Prof. Suresh
Nagpal, Chairman, Krupanidhi Educational
Trust, Bangalore, India, Prof. Sunil
Dhamanigi, Secretary, Krupanidhi
Educational Trust, Bangalore, India and
Dr. Amit Kumar Das, Professor and
Principal, Krupanidhi College of Pharmacy,
Bangalore, India, for providing facilities to
carry out this work.
Indian J Physiol Pharmacol 2006; 50(2) Pharmacological Evaluation of Pachyrrhizus Erosus 151
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