International Journal of Drug Development and Research

Key words

Anticonvulsant activity, Terminalia chebula, seizures, MES, PTZ, PC

INTRODUCTION

Epilepsy is a neurological disorder in which a person has two or more recurrent unprovoked seizures. Seizure is a paroxysmal event that is due to abnormal, excessive and hypersynchronous discharge from an aggregate of central nervous system neurons. Epilepsy is the second most common disorder of the central nervous system after stroke and up to 5% of world population develops epilepsy in their lifetime [1]. The current therapy of epilepsy with modern antiepileptic drugs is associated with side effects, dose-related and chronic toxicity, as well as teratogenic effects, and approximately 30% of the patients continue to have seizures with current antiepileptic drugs therapy. Traditional system is believed to be an important source of chemical substances with potential therapeutic effects. Herbs may have antiepileptic effects in several ways. Some herbs may increase brain levels and/or the binding of nerve transmitter gamma aminobutyric acid (GABA), which quiets nerve activity [2,3]. Concurrently, phytochemicals identified from traditional medicinal plants are presenting an exciting opportunity for the development of new types of therapeutics. This has accelerated the global effort to harness and harvest those medicinal plants that bear substantial amount of potential phytochemicals showing multiple beneficial effects in convulsion.

Terminalia chebula Retz. (Combretaceae) is one of the ingredients in a polyherbal formulation, “Geriforte” an Ayurvedic Rasayana that is known to promote physical and mental health and improve immune power of the organism so that the body can tolerate any nature of stress [4,5]. Terminalia chebula also possesses Laxative, Hypolipidemic, Antioxidant, Hepatoprotectant, Antiviral and Antibacterial activity [6,7]. The plant is an important constituent of an herbal formulation contains the name TRIPHALA is very popular traditional medicine for chronic disorder like diabetes, nervine disorder & epilepsy [8,9]. The aim of the present study was, therefore, to evaluate the anticonvulsant potential of the ethanol extract of fruits of Terminalia chebula (EETC) in experimental animal models, to provide a pharmacological justification for the traditional use of the plant’s fruits in the management of epilepsy in some rural parts of India.

MATRERIALS AND METHODS

Plant material

The fruits of Terminalia chebula were collected from Nagaon, Assam and it was authenticated by Dr. Shiddamallayya N, Regional Research Institute (Ay.) Ashoka Pillar, Bangalore. The fruits of Terminalia chebula were separated and shade dried. The dried material was reduced to a coarse powder and was successively extracted in soxhlet apparatus using petroleum ether, chloroform and alcohol (according to their increasing polarity for 24 hrs). The solvents were redistilled and ethanolic extract was concentrated under reduced pressure and air dried. The yield of ethanolic extract was found to be 36%w/w. The extract was solubolized in aqueous solution.

Experimental animals

Swiss mice of either sex, 8-10 weeks old, weighing about 25-30 g were used in experiments. Animals were housed in polypropylene cages maintained under standard condition (12 hours light / dark cycle; 25 ± 30C, 45-65% humidity) and had free access to standard feed and water ad libitum. All the animals were acclimatized to laboratory condition for a week before commencement of experiment. All experimental protocols were reviewed and accepted by the Institutional Animal Ethical Committee (IAEC) prior to the initiation of the experiment.

Acute toxicity study

The acute oral toxicity of ethanolic extract of Terminalia chebula (EETC) were determined in 3 hours fasted female albino mice by fixed dose method according to OECD guidelines No. 420 [10].

Assessment of Anticonvulsant activity

Maximal Electrical Shock (MES) -induced seizures: The animals were divided in four groups (n = 6). Group I served as vehicle control group. Groups III, and IV served as test groups treated with the extract (200 and 500 mg/kg, p.o., 60 min), respectively, and group II served as reference standard group received phenytoin (25 mg/kg, i.p., 20 min), prior to the induction of convulsion. The number of animals protected from hind limb tonic extension seizure (HLTE) and the time spent in this position were determined for each dose group [11].

Pentylenetetrazole (PTZ) -induced seizures: The animals were divided in four groups (n = 6). Group I served as vehicle control group. Groups III, and IV served as test groups treated with the extract 200 and 500 mg/kg, p.o. The EETC was administered 60 min before the subcutaneous injection of PTZ (80 mg/kg). Group II received diazepam (2.0 mg/kg, i.p.) as a reference standard. The animals were observed for onset of convulsion upto 30 min after PTZ. Hind limb extension was taken as tonic convulsion. The onset of tonic convulsion and the number of animals convulsing or not convulsing within the observation period were noted. The ability of the plant extract to prevent or delay the onset of the hind limb extension exhibited by the animals was taken as an indication of anticonvulsant activity [12, 13].

Picrotoxin (PC) -induced seizures: The animals were divided in four groups (n = 6). Group I served as vehicle control group. Groups III, and IV served as test groups treated with the extract 200 and 500 mg/kg, p.o. The EETC was administered 60 min before the subcutaneous injection of picrotoxin (10 mg/kg, i.p.). Group II received diazepam (2.0 mg/kg, i.p.) as a reference standard. The animals were observed for onset of convulsion upto 30 min after PC. Hind limb extension was taken as tonic convulsion. The onset of tonic convulsion and the number of animals convulsing or not convulsing within the observation period were noted. The ability of the plant extract to prevent or delay the onset of the hind limb extension exhibited by the animals was taken as an indication of anticonvulsant activity [11, 13].

Statistical analysis

All the values are expressed as mean ± SEM. Statistical differences between means were determined by oneway ANOVA followed by Dunnett’s post hoc test. p<0.05 was considered as significant.

RESULT

Phytochemical screening

The preliminary phytochemical screening of the ethanolic extract of Terminalia chebula revealed the presence of carbohydrates, anthraquinone glycosides, Saponin glycosides, flavanoids, tannins and polyphenols.

Acute toxicity study

Acute oral toxicity studies of the ethanolic extract of Terminalia chebula did not exhibit any sign of toxicity up to 2000 mg/kg body weight. Since there was no mortality of the animals found at highest dose, hence 200 (1/10th) and 500 (1/4th)) mg/kg, p.o. doses of extract were selected for evaluation of Anticonvulsant activity.

Anticonvulsant activity

Maximal electroshock produced hind limb tonic extension seizures (HLTE) in all the animals. The vehicle-treated mice showed tonic hind limb extension for duration of 14.83 ± 0.40 sec. The EETC at doses of 200 and 500 mg/kg, respectively, protected 17% and 50% of mice and significantly reduced the duration of the seizures. However, phenytoin completely abolished the MES-induced tonic seizures in all the animals. (Table. 1).

Pentylenetetrazole produced tonic seizures in all the animals used. The EETC, in doses of 200 and 500 mg/kg, respectively, protected 33% and 83% of mice against seizures, and significantly delayed the latency of the seizures. The standard antiepileptic drug, diazepam inhibited seizures completely. (Table. 2).

Picrotoxin produced tonic seizures in all the animals. The EETC (200 and 500 mg/kg) did not affect the incidence of seizures, but significantly prolonged latency of seizures. The standard antiepileptic drug, diazepam protected 83% the animals from convulsions. (Table. 3).

DISCUSSION

The observation of present study indicates that ethanol extract of T. Chebula (EETC) possesses anticonvulsant activity in mice. GABA is the major inhibitory neurotransmitter in the brain while glutamic acid is an excitatory neurotransmitter in the brain. The inhibition of GABA neurotransmitter and the enhancement of the action of glutamic acid have been shown to be the underlying factors in epilepsy. The present study shows that the ethanol extract of fruits of T. Chebula protected some of the animals against seizures induced by maximal electroshock. Antiepileptic drugs which inhibit voltage-dependent Na+ channels, such as phenytoin can prevent MES-induced tonic extension [14, 15].. Pentylenetetrazole may elicit seizures by blocking GABA/Cl- channel complex. Picrotoxin induces seizure, by blocking the chloride channels linked to GABA-A receptor.. Diazepam, a standard antiepileptic drug is believed to produce their effects by enhancing GABA mediated opening of chloride channel on GABA-A receptor leading to more chloride ion entering the neuron which in turn decreases the neuronal activity in the brain [16]. In the present study diazepam shown to antagonize the seizure induced pentylenetetrazole and picrotoxin. The extract was also shown to delay the latency of pentylenetetrazole and picrotoxin induced seizures, suggesting that the extract exhibiting anticonvulsant affect, probably by opening the chloride channels associated with GABA receptors. Thus, in conclusion, T. Chebula possesses anticonvulsant property against the MES, PTZ and PC induced seizures. From the above result, further investigation is warranted in order to isolate and identify the specific molecules which are responsible for the anticonvulsant activity.

Conflict of Interest

NIL

Source of Support

NONE

Tables at a glance

Table 1 Table 2 Table 3

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