Analgesic activity of Tamarindus indica
NS Dighe1, SR Pattan1, SA Nirmal2*,
RS Kalkotwar1, VM Gaware1
and MB Hole1
1Department of Pharmaceutical Chemistry, 2Department
of Pharmacognosy, Pravara Rural
ABSTRACT
Tamarindus
indica (Caesalpiniaceae)
bark is used in the treatment of pain traditionally, present work was
undertaken to prove this scientifically by using suitable animal screening
models as hot plate test and acetic acid induced writing test at the dose of 50
mg/kg, i.p. Petroleum ether extract showed significant increase in reaction
time as compared to other extracts. Preliminary phytochemical test showed
presence of sterols and triterpenes in the extract; hence these compounds might
be responsible for analgesic activity.
INTRODUCTION:
Tamarindus
indica (Caesalpiniaceae) is
commonly known as ‘chinch’ in marathi. Leaves of the plant are alternate,
spiral, and petiolate. Leaflet blades are 8.75 mm long and 3-10 mm wide.
Flowers are in affronting racemes, sepals are creamy white, petals are
conspicuously veined with red seeds up to 3-12, obovate, turnate, and pods are
curved constricted. Seed are not splitting, non fleshy, 4-140 mm long and 15-30
m wide.1 Traditionally Leaves are used as antifungal and
antibacterial. Fruit is smolucidal and shows core salivation. Seeds are used as
antioxidant.Various chemical compounds viz. 5-hydroxy-2-oxotexa-3,5-dienal, α
& β-tocoferol, 2-hydroxy-3’,4’-dihydroxy acetophenone, epicatechin,
and tartaric acid were isolated from T.
indica. Objective of
present research is to study analgesic action of bark of plant T. indica.
MATERIAL AND METHODS:
Plant
material
The fresh bark of plant T. indica L. was collected from Durgapur, Ahemadnagar district,
Maharashtra in August 2007 and authenticated by Dr. Ashok Bhosale, Department
of Botany, P. V. P. College, Loni. A voucher specimen was deposited in the
department (Voucher specimen No. TI-21).
Animals:
Male Swiss albino mice weighing 25-28 gm
were housed under standard laboratory condition. The animal had free access to
food and water. The animal ethical committee of institute approved all the
experimental protocols of study.
Extraction:
Dried and coarsely powdered bark of T. indica was extracted successively in
Soxhlet extractor using solvents viz. petroleum ether, and ethanol. The marc
left was extracted by reflux condenser using water as solvent. All the extracts
were vacuum dried to produce respective extract respectively.
Evaluation
of analgesic activity
Hot
plate method: The analgesic
activity was evaluated using hot plate method.3 The mice were
divided into 5 groups (n=6). The first group served as control and received
vehicle (2% tween 80 into saline water), second group received standard drug
pentazocin lactate (10 mg/kg, i. p.). The animals from 3rd to 5th groups were
treated with petroleum ether, ethanol and aqueous extracts (50 mg/kg, i.p.,
each) in vehicle. Mice were placed individually on hot plate maintained at 55±10C
and latency to lick the paws was noted. The basal reaction time was noted
before and 30,
Fig.
1.
Effect of various extracts (50 mg/kg, i.p.) of T. indica bark on thermal stimulus-induced pain
(Hot plate test)
Note:
All the values are expressed as mean ± SEM; n = 6; @P
< 0.0001; *P < 0.01 significant compared to control group. Only
significant data are presented.
Fig.
2.
Effect of various extracts of T. indica bark on acetic acid-induced writhing
Note: All the values are
expressed as mean ± SEM; n = 6, *P < 0.05 significant compared to control
group.
Fig.
3.
Effect of various extracts of T. indica bark on onset of acetic acid-induced writhing
Note: All the values are expressed as mean ± SEM; n = 6, *P < 0.001
significant compared to control group
60, 90, 120, 150 and 180 min after the
administration of treatment. The experiment was terminated 20 sec after their
placement on hot plate to avoid damage to the paws.
Acetic acid induced writhing
test: Peripheral analgesic
activity was evaluated using acetic acid induced writhing test.4
Mice were prescreened 48 hrs before actual experiment and those were sensitive
to the acetic acid induced writhing were divided into five groups of six animals each. The animals received petroleum
ether, ethanol, and aqueous extracts of T.
indica bark (50 mg/kg, i. p., each) in vehicle or standard paracetamol (50
mg/kg, i. p.) or vehicle (2% tween 80 into saline water) 30 min before
intraperitoneal injection of 0.1 ml of 0.6% solution of acetic acid. Mice were
placed individually in glass beaker after administration of acetic acid 5 min
were allowed to elapse. The mice were then observed for the period of 30 min
and then writhes were recorded for each animal.
Statistical analysis:
All data were
expressed as mean ± SEM. The statistical analysis of all the observations was
carried out using one-way ANOVA followed by the multiple comparison test of
Tukey- Kramer, wherever necessary. P < 0.05 was considered as significant
compared with the control group.
RESULTS
AND DISCUSSION:
Hot plate test: In the hot plate test, petroleum ether extract (50
mg/kg, i.p.) showed significant increase in reaction time without any behavioural
effects as compared to standard
drug pentazocine (10 mg/kg, i.p.) (Fig. 1). Ethanol and aqueous extracts (50
mg/kg, i.p.) did not show significant results (data not shown). The hot plate
test is the specific central antinociceptive test. Petroleum ether extract
showed significant results in this test so we can say that there may be
involvement of opioid receptors. The opioid agents exert their analgesic action
via supraspinal (µ1, κ 3, δ1, σ2)
and spinal (µ2, κ1, δ2) receptors.5
Therefore it is possible that the extract exert their effect through central opioid receptor or promoted release of endogenous
opioid peptides.
Acetic acid-induced writhing test: Petroleum ether extract (50 mg/kg, i.p.)
produced significant inhibition of writhing reaction induced by acetic acid
compared to control group (fig. 2). Similarly this extract delayed onset of writhing response significantly compared to
control and other extracts (fig. 3). Intraperitoneal injection of acetic acid
produces pain through activation of chemosensitive nociceptors6 or
irritation of the visceral surface, which lead to liberation of histamine,
bradykinins, prostaglandins, and serotonin.7 Thus antinociceptive
activity of opioid partial agonist and non-steroidal anti-inflammatory agents
can be determined by writhing test.8 The mechanism of analgesic
effect of extracts of T. indica bark could probably due to blockage of
effect or release of endogenous substances that excite pain nerve endings.
Overall we can say that petroleum ether extract of T.
indica bark showed potent antinociceptive activity in both tests.
Prostaglandins and bradykinins were suggested to play an important role in
nociception.9,10 Preliminary phytochemical tests showed presence of
sterols and triterpenes in petroleum ether extract. Sterols are reported to
inhibit prostaglandin synthesis.11,12 Some sterols and triterpenes
are responsible for anti-inflammatory and analgesic activity.13 From
this, we can conclude that antinociceptive activity observed may be due to sterols and triterpenes.
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Received on 21.04.2009
Accepted on 10.05.2009
© A&V Publication all right reserved
Research Journal of Pharmacognosy and Phytochemistry. 1(1): July.-Aug. 2009, 69-71