Experimental evaluation of analgesic property of bark skin of Saraca indica ( Ashoka ) and Shorea robusta ( Shal )

Article history: Received on: 04/01/2014 Revised on: 07/02/2014 Accepted on: 04/03/2014 Available online: 30/03/2014 The aqueous and alcoholic extracts of bark skin of Saraca indica (Ashoka) and Shorea robusta (Shal) were evaluated for their analgesic activity in Swiss albino rats by making use of different pain models such as, tail immersion test, tail clip method and writhing induced by 4% NaCl solution. The aqueous and alcoholic extract of Saraca indica and Shorea robusta showed significant analgesic activity at 300 mg/ Kg body weight in Swiss albino rats as compared with control rats from physical, thermal and chemical stimulus of evaluation techniques. The analgesic activity might have been attributed to the presence of alkaloids, steroids in these plants as revealed from phytochemical analysis. On the basis of these observations it was concluded that Ashoka and Shal has got analgesic property, however further experimental as well as clinical evaluations are necessary.


INTRODUCTION
Analgesia has got the utmost importance in the success if any surgery and parasurgical procedures.In Ayurvedic texts a number of herbs as well as various parasurgical measures regarding analgesia have been vividly described.Shorea robusta (Shal) and Saraca indica (Ashoka) are important traditional Indian medicinal plants used in various ailments and rituals and the indigenous use of these plants as a medicament for treatment of various inflammatory conditions is well documented in literature.Shorea robusta (Shal) belongs to the family Dipterocarpaceae (two-winged fruit), which is most commonly found in Indonesia, but can also be seen in Malaysia, the Philippines and certain parts of Northern India (Wani et al., 2012).The powdered stem, bark or bark paste is applied to stop bleeding and promote healing of cuts among the tribal inhabitants of southern Bihar and the Kondhs of south-western Odisha, India (Ganesan et al., 2006).Ashoka is the most ancient tree of India, generally known as "shok briksh", having botanical name Saraca asoca (Roxb.),De.wild or Saraca indica belonging family Caesalpinaceae.Saraca indica is used as .

Experimental animal
Thirty six healthy Swiss albino rats weighing between 200-300 grams were divided in six groups.Each group comprised of six rats with 50% sex ratio (Table 1).The experiments were carried out in accordance with the guidelines of Animal Ethics Committee, Nagpur Veterinary College, Nagpur.

Models for assessing analgesic activity
The analgesic tests were carried out by the method described by Ghosh (2005).

Tail immersion test
The water was taken in a beaker and heated up to 55-60 degree and temperature was monitored with thermometer continuously.The rats were held in a suitable position with tail protruding out.The tail up to 5 cm was dipped in a beaker containing water at 55± 0.5°C.The time taken in seconds to withdraw the tail clearly out of water was taken as the reaction time.
Thus the initial time in seconds before administration of drug for all rats from each group was recorded.The aqueous and alcoholic extracts of Shorea robusta and Saraca indica were administered to the groups keeping oral route constant for every administration.The reaction time in seconds was then recorded after administration of drug at the interval of 45 minutes, 75 minutes, and 150 minutes of all groups individually.Mean of these readings was taken as reaction time which was compared with the control group.
Tail clip method (Bianchi and Franceschini, 1954) In this method, an artery clip with rubber sleeves was applied to the base of rat's tail for 30 seconds.Control rats made continuous efforts to dislodge the clip by biting it the pressure exerted by the clip was so adjusted that it was just sufficient to make all control rats to respond.
Analgesics made the mice indifferent to the clip.The aqueous and alcoholic extracts of Saraca indica and Shorea robusta were administered to the groups keeping oral route constant for every administration and 30 minutes later the clip was applied.The time taken in seconds to respond clearly was taken as the reaction time.Thus the initial time in seconds before administration of drug for all rats in each group was recorded.The reaction time in seconds was then recorded after administration of drug at interval of 30 minutes, 45 minutes and 75 minutes of all groups individually.Mean of these three reading was taken as reaction time which was compared with the control group.

Writhing induced by 4% NaCl solution
The writhing test with 4% NaCl in rats is a sensitive and specific test for predicting analgesic activity of a compound in man.It is also useful for examining changes in analgesic activity of drugs during chronic (repaeated) administration.Male rats (200 ± 20 g) were injected intra-peritoneally with 1 ml/ kg NaCl.Rats that do not exhibit writhing within 30 seconds were discarded.The onset of writhing is much quicker (30 seconds) than that with phenylquinone or acetic acid, and lasts for a shorter period (about 3 min).The aqueous and alcoholic extracts of Saraca indica nd Shorea robusta was administered to the groups (keeping oral route constant for every administration) 20 to 30 minutes before administering NaCl solution.The animals (rats) showing no response was defined as analgesic positive.The percentage protection at each group was calculated.No response= analgesic positive Writhing response = analgesic negative

Statistical analysis
The data was analysed by completely randomised design (CRD) to know the level of significance.Mean and critical difference of all the characters under study were calculated as per standard procedure (Snedecor and Cochran, 1989)

Phytochemical analysis
Phytochemical analysis of both the extracts of Ashoka revealed the presence of tannin, essential oil, terpenoid and steroid.Both extracts of Shal has tannin, resins, terpenoid, and essential oil.

Analgesic activity
The results of tail immersion method, tail clip method and writhing test are given in Table .2, 3 and 4 and Figure 1, 2 and 3 respectively.The aqueous and alcoholic extract of Saraca indica and Shorea robusta showed significant analgesic activity at 300 mg/ Kg body weight in Swiss albino rats (P<0.01) when compared with control rats from the above physical, thermal and chemical stimulus of evaluation techniques.

DISCUSSION
In the various texts of Ayurveda a number of herbs, organic or inorganic drugs have been described that are having analgesic property.Most of these drugs are widely used therapeutically to relieve pain but these drugs needs to be reestablished on modern lines.Ashoka and Shal are such herbs which are used very commonly.Ashoka has been mentioned as having analgesic properties in previous studies (Pradhan et al., 2009) which corroborates the finding of the present study.Similarly Shal was also reported to have significant analgesic activity as assessed by using different central and peripheral pain models in a previous study (Wani et al., 2012).The oleoresin exuded from the cut bark reported to have astringent and detergent properties (Wani et al., 2012) and the powdered stem, bark or bark paste is used to stop bleeding and promote healing of cuts among the tribal inhabitants of southern Bihar and south-western Odisha, India (Ganesan et al., 2006).S. robusta leaf extract was found to possess significant analgesic activity (Jyoti et al., 2008) and its resin along with some other constituents has also shown potential in wound healing (Datta et al., 2011).The analgesic activity of aqueous and alcoholic extract of Saraca indica and Shorea robusta can be attributed to the presence of alkaloids and steroids as revealed from phytochemical analysis of the present study.

CONCLUSION
On the basis of observations of the present study it was concluded that bark skin of Ashoka and Shal have got analgesic property, however further experimental as well as clinical evaluations are necessary.

Fig. 1 :
Fig. 1: Bar diagram showing analgesic activity of aqueous and alcoholic extracts of Ashoka and Shal by tail immersion test.

Table . 2
: Screening of analgesic activity of aqueous and alcoholic extracts of Ashoka and Shal by tail immersion test.Before drug, AD-After drug, Diff-Difference, SE± -standard error, **-significance Table.3: Screening of analgesic activity of aqueous and alcoholic extracts of Ashoka and Shal by tail clip method.Before drug, AD-After drug, Diff-Difference, DT-Difference total, SE± -standard error, **-significance)

Table . 4
: Screening of analgesic activity of aqueous and alcoholic extracts of Ashoka and Shal by writhing test.