Anti-Depressant Activity of Ethanolic Extract of Citrullus vulgaris Seeds in Experimentally Induced Depressed Mice

 

R. S. Adnaik*, P. S. Gavarkar, S. K. Mohite, C, S Magdum

Rajarambapu College of Pharmacy, Kasegaon, Tal Walwa, Dist Sangi 415404, MS, India

*Corresponding Author E-mail: rahul.cology@gmail.com

 

ABSTRACT:

Mental depression is a chronic illness that affects a person’s mood, thoughts, physical health and behaviour. Currently used antidepressant drugs such as tricyclic antidepressants and selective serotonin reuptake inhibitors (SSRI) are showing various side effects and thus, the search for a new antidepressant herb without side effects is important. The present work was aimed to study the antidepressant activity of ethanolic extract of Citrullus vulgarsis (Cucurbitaceae) at doses of 100mg and 200mg/kg against forced swimming test and tail suspension test in mice. Imipramine (30mg/kg, i.p) was used as reference standard and it showed significant antidepressant activity in rodents. The anti-depressant effects of Citrullus vulgaris in FST and TST were more prominent at 200 mg/kg when compared to lower dose of same fraction. The significant antidepressant effects of Citrullus vulgaris could be due to strong and effective concentration of the active constituent. In conclusion, the present study suggested that Citrullus vulgarsis extract possesses potential antidepressant effects which could be of therapeutic interest for using in the treatment of patients with depressive disorders.

 

KEYWORDS: Citrullus vulgarsis, antidepressant activity, tail suspension test, forced swim test, Imipramine.

 


INTRODUCTION:

Depression is an affective disorder characterized by change in mood, lack of interest in the surroundings, psychomotor retardation and melancholia. A number of neurochemical theories exist and a number of synthetic antidepressant drugs are available in practice, however their effectiveness does not helps in improvement of subjects suffering from this disorder1. So also the side effects and the drug interactions are major restrictions in its clinical utility. Antidepressant drugs such as tricyclic antidepressants and selective serotonin reuptake inhibitors (SSRI) are used to treat depression showing various side effects and thus, the search for a new antidepressant herb without side effects is important2.

 

Herbal medicines are widely used across the world for their therapeutic effectiveness and least side effects, which in turn has accelerated the scientific research regarding the antidepressant activity. Indian traditional system of medicine, claims a vast number herbal constituents used in the treatment of psychiatric disorders.

 

Citrullus vulgaris (Schrad), water melon, belongs to family cucurtbitaceae cultivated throughout the earth. The watermelon fruit has deep green or yellow colored smooth thick exterior rind with gray or light green vertical stripes. Inside the fruit is pink, red or even yellow in color with small black seeds embedded in the middle third of the flesh. Generally, watermelon flesh is the main consumable portion; however, outer rind is also used in some parts of the world3,4. Watermelon with red flesh is a significant source of lycopene. Its seeds are cooling, diuretic and strengthening5,6, aphrodisic5; seeds are reported also as demulcent, vermifuge and nutritive6. Fruit contains carotene, lycopin, mannito, 20-40% of oil from seeds. Seeds rich source of the enzyme urease. Juice contains citrulline to the extent of 0.17%5.

 

The present has been undertaken to study the antidepressant effects of the ethanolic extracts of C. vulgaris seeds in rats.

 

MATERIALS AND METHODS:

Plant Material

The seeds of Citrullus vulgaris were collected from local market of Kolhapur city and were identified and authenticated.

 

Extraction

The seeds were powdered and subjected to extraction in soxhlet apparatus using ethanol as solvent. The extract was concentrated by distilling the solvent. The concentrated extracts were evaporated on water bath (40-500C) to dryness. The extracts were stored at 40C for further phytochemical screening.

 

Preliminary Phytochemical Screening

The ethanolic extract was subjected to phytochemical tests for the presence of different constituents using standard methods7.

Experimental Animals

Adult male Swiss albino mice weighing 25-35 gm were used in this study. The animals were housed at 24±20C with 12:12 h light and dark cycle. They had free access to food and water ad libitum. The animals were acclimatized for a period of 7 days before the study. The animals were fasted overnight just prior to the experiment but allowed free access to drinking water. All the experiments were carried out in accordance with the guidelines of Institutional Animal Ethics Committee. The experimental protocol was approved by the institutional ethical Committee for the Purpose of Control and Suspension of Experiments on Animals (CPCSEA) under Ministry of Animal Welfare Division, Government of India, New Delhi

 

Acute Toxicity Study:

The procedure was followed as per OECD 423 guidelines. The extract was administered orally at a dose 2000mg/kg body weight to different groups of mice and observed for signs of behavioural8. Neurological toxicity and mortality was observed for 14 days.

 

Screening of Anti Depressant Activity

Forced Swim Test

The method described by Porsolt, et. al. was used in our study9, 10. Mice were divided into 4 groups of six animals each.

Group I: Control (normal saline-5ml/kg)

Group II: Imipramine (20mg/kg)

Group III: Ethanolic extract of Citrullus vulgaris (100mg/kg)

Group IV: Ethanolic extract of Citrullus vulgaris (200 mg/kg)

 

The test apparatus consists of a transparent rectangular glass jar (25x12x25 cm3) filled to a 15cm depth with water (24 ± 10C). In the pre-test session, every animal will be placed individually into the jar for 15 mins, 24 hrs prior to the 6mins swimming test, in which the duration of immobility is recorded for the last 5mins. Group I receive only saline treatment and animals from group II, III and IV received oral administration of the graded dose of Imipramine (20mg/kg p.o.) and Citrullus vulgaris seed extract (100 and 200mg/kg) respectively administered one hour prior to final swimming test session. The period between when the mouse was immersed and when no further attempts to escape were made (apart from the movements’ necessary to keep its head above the water) will be recorded as the immobility time.

 

Tail Suspension Test

The method described by Steru, et. al. was used in our study11. This method is based on the observation that a mouse suspended by the tail shows alternating agitation and immobility the immobility is an indicative of a state of a depression. Swiss Albino mice will be divided into 4 groups of six animals each.

 

Group I: Control (normal saline-5ml/kg)

Group II: Imipramine (20mg/kg)

Group III: Ethanolic extract of Citrullus vulgaris (100mg/kg)

Group IV: Ethanolic extract of Citrullus vulgaris (200 mg/kg)

 

The mice were being individually suspended 50 cm above the surface of table with an adhesive tape placed 1 cm away from the tip of the tail 51. Immobility duration was recorded for the last 5 minutes during 6 minutes. Mice were being considered immobile only when they hung passively and were completely motionless. Single administrations of Citrullus vulgaris seeds extract (100, 200mg/kg) and  Imipramine (20mg/kg .) were be given one hr prior to test.

 

Statistical Analysis

The statistical analysis of various studies were carried out using paired ‘t’ test and analysis of variance (ANOVA) followed by Dunnet’s ‘t’ test, p<0.05 were considered as significant.

 

RESULTS:

Preliminary Phytochemical Screening

The ethanolic seed extract of C. vulgaris showed the presence of saponins, terpenoids, alkaloids, phenols, steroids and flavonoids.

 

Forced Swim Test:

Citrullus vulgaris at doses of 100 and 200 mg/kg were studied in the forced swim test model of depression in mice. The extract induced a significant (P<0.05) reduction in the immobility duration in both dose levels, when compared to the vehicle treated groups. The effect was found to be dose dependant. However, the effect of Citrullus vulgaris at 200mg/kg showed better activity than standard drug Imipramine (20mg/kg) represented in table 1.


 

 

Table 1: Effects of Citrullus vulgaris seed extract on duration of immobility in the Forced swim test.

Group

Treatment

Dose (mg/kg)

Time of immobility in seconds

I

Control (normal saline)

5ml/kg

165 ± 1.459

II

Imipramine (Standard )

20mg/kg

109 ± 1.675**

III

Ethanolic extract of Citrullus vulgaris

100mg/kg

128 ± 2.376*

IV

Ethanolic extract of Citrullus vulgaris

200 mg/kg

117 ± 2.055**

Ethanolic extract of Citrullus vulgaris. One way ANOVA followed by Dunnet’s test. Values are mean ± S.E.M ( n = 6), in each group *p < 0.05, **p < 0.01 when compared to control.


Tail Suspension Test:

The Citrullus vulgaris extract was further evaluated in the Tail Suspension Test model of Depression. Citrullus vulgaris at doses 100 and 200 mg/kg significantly reduced (P<0.05) the immobility duration in a dose dependent manner when compared to the vehicle treated groups. Imipramine (20mg/kg, po), the standard antidepressant Imipramine also produced a significant decrease in the immobility time (table 2).

 

Table 2: Effects of Citrullus vulgaris seed extract on duration of immobility in the Tail suspension test

Group

Treatment

Dose (mg/kg)

Time of immobility in seconds

I

Control

(normal saline)

5ml/kg

158.17±2.62

II

Imipramine (Standard )

20mg/kg

76.34±2.11**

III

Ethanolic extract of Citrullus vulgaris

100mg/kg

116.17±2.81*

IV

Ethanolic extract of Citrullus vulgaris

200 mg/kg

94.17±2.45**

Ethanolic extract of Citrullus vulgaris. One way ANOVA followed by Dunnet’s test. Values are mean ± S.E.M ( n = 6), in each group *p < 0.05, **p < 0.01 when compared to control.

 

DISCUSSION:

The prevention and management of stress disorders remains a major clinical problem. Hence it is very important to address these problems and find effective remedies. Though several drugs are available, all are associated with some limitations and there is an urgent need for alternative medications for these disorders12. Depression is a senile neurological disorder that is widely prevalent to modern fast paced life. Stressful lifestyle facilitates the evolution of depressive disorder as the stress can influence the function of central nervous system by altering a number of neurotransmitters, endocrine and neuroendocrine systems13. The purpose of this study was to evaluate the antidepressant activity of methanolic extract of Citrullus vulgaris seeds by using behavioural animal models.

 

Forced Swim Test (FST) developed and Tail Suspension Test (TST) developed induces unavoidable stress to rodents which reflects a state of behavioral despair that is similar to human depression. A normal animal tested in FST and TST submitted to a non-soluble aversive situation shows alternate between agitation and immobility. The agitation reflects state of searching which requires energy consumption while immobility is energy conservation14. The swimming and immobility behaviors are sensitive to serotoninergic agents, such as the SSRI’s agents. Based on these findings it can be suggested that Citrullus vulgaris which is able to reduced the immobility time and increase swimming behavior in the mice exposed to these paradigms can exert its effect through a mechanism similar to that of the SSRI’s via serotonin system. More over Imipramine belongs to the class of tricyclic anti-depressant drugs which blocks the reuptake of NE and 5-HT into their respective neurons. Hence Citrullus vulgaris can also mediate its activity through the same mechanism as that of Imipramine.

The anti-depressant effects of Citrullus vulgaris in FST and TST were more prominent at 200 mg/kg when compared to lower dose of same fraction. The significant antidepressant effects of Citrullus vulgaris could be due to strong and effective concentration of the active constituent.

 

CONCLUSION:

From the study it can be concluded that the ethanolic extract of Citrullus vulgaris seeds possess antidepressant activity. The results obtained were almost equal to the existed familiar drugs imipramine. Therefore the present findings support the use of Citrullus vulgaris as an antidepressant and give a clue to development of new antidepressant agents from natural source.  However further studies are needed to characterize the mechanism of antidepressant effect of Citrullus vulgaris which could be used as effective therapeutic agent.

 

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Received on 08.03.2014          Modified on 05.05.2014

Accepted on 10.05.2014         © RJPT All right reserved

Research J. Pharm. and Tech. 7(6): June, 2014; Page  660-662