PHYTOCHEMICAL AND ANTICONVULSANT STUDIES ON METHANOL EXTRACT OF THE ROOTBARK OFUVARIA CHAMAEP. BEAUV. (ANNONACEAE)

ABSTRACT

Uvariachamae P. Beauv. (Annonaceae) is widely distributed inAfrica, the plant species are used in traditional medicine as an anti-inflamatory, antimalarial, and analgesic. It is also used for treatment of jaundice, epilepsy and microbial infections. The powdered rootbark of U.chamaewas extracted with methanol using maceration method and the resulting crude methanol extract (CME) was solvent fractionated to give hexane (HF), chloroform (CF), ethylacetate (EF) and n-Butanol (BF) fractions. Chloroform fraction was step-wisely eluted in a silica gel packed column to afford eleven fractions S₁-S_12.Fraction S₆was subjected to Preparative Thin Layer Chromatography (PTLC), using hexane: ethyl acetate (5:3) as solvent system led to the isolation of Quercetin. The structure of the compound was elucidated using chemical test and spectroscopic techniques (UVand 1D-NMR) and by comparison with reference spectral data.The preliminary phytochemical screening of CME revealed the presence of carbohydrates, alkaloids, flavonoids, saponins, tannins, cardiac glycosides, steroids and triterpenes. The acute toxicity study was carried out using Lorke’s method and the anticonvulsant activity was studied using maximal electroshock induced seizure test (MES) and subcutaneous pentylenetetrazole induced seizure test (Sc. PTZ). The LD₅₀ of the crude methanol extract (CME) was estimated to be 1131.37mg/kg in mice. The crude methanol extract(CME) was found to increase the mean time of recovery from seizures in MEST compared to negative control. The absence of anticonvulsant activity in MEST suggests that CME may not be useful in the treatment of generalized tonic clonic and partial seizures. In Sc.PTZ test, the CME at dose of 30mg/kg protected 80% of mice against pentylenetetrazole and significantly (P˂ 0.05) delayed the onset of seizure. Standard antiepileptic drugs such as valproic acid are thought to produce their effects by enhancing GABA mediated inhibition in the brain. In this regard, the CME have demonstrated anticonvulsant activity and may be useful in treatment of generalized absence seizure.

1.0 INTRODUCTION

1.1 Natural product

Natural products have been and still are an inexhaustible source of drugs. The medicinal properties of plants predate human history and are the basis of much of modern medicine. Traditional medicine has been defined as the knowledge, skills and practices based on the theories, beliefs and experiences indigenous to different cultures, used in the maintenance of health and in the prevention, diagnosis, improvement or treatment of physical and mental illness (WHO, 2013). For many years, traditional medicine has proven to be effective in healthcare, disease management and prevention (Philipson, 2001). The use of traditional medicine is not limited to developing countries. Statistically, 70% of medical doctors in France and Germany regularly prescribe traditional medicine (Murray and Pizorno, 2000). Examples of drugs used in orthodox medicines that are derived from plants are: (i) Quinine: obtained from Cinchona officinalis bark, an antimalarial which lead to the synthesis of 8-amino and 4-amino quinoline antimalarial; (ii) Artemisinin: from Artemisia annua served as a lead for the synthesis of (iii) artemether, (iv) arteether, and (v) artesunate as antimalarials; (vi) Morphine: a nacortic analgesic from Papaver somniferum served as a lead compound to the synthesis of naloxone and buprenophine; (vii) Cocaine: from Erythroxylon coca leaves served as a lead for more potent and less toxic local anaesthetics such as procaine and lidocaine; (viii) Digoxin: from foxglove (Digitalis purpurea, D. lanata) is still the best drug for the treatment of myocardial dysfunction; there is yet no synthetic drug capable of replacing the constituents of Digitalis (Olaniyi, 1989). The use of herbal medicine is becoming increasingly popular. There are various reasons for this upsurge; these are safety, availability, ease of accessibility or convenience, and low cost as compared to conventional medicine (Winslow and Kroll,1998).

Nevertheless, herbal medicine can be harmful. They are heterogeneous in composition and impose challenges to quality control, assurance and the regulatory processes. Some of them contain heavy metals such as mercury, lead, corticosteroids and poisonous organic compounds in harmful amounts (Sanjoy and Yogeshwer, 2003). Thus the need to purify and isolate only the active components.

1.2 Artemisinin based analogues

Artemisinin (ii) is a sesquiterpinelactone isolated from the plant Artemisia annuaand its semi-synthetic derivatives are such as, artemether (iii), arteether (iv), artesunate (v) are group of drugs that possess the most rapid action of all current drugs against Plasmodium falciparum malaria (White, 1997). In some areas of South-East Asia, combinations of artemisinins (ii) and mefloquine (ix) offer the only reliable treatment for uncomplicated malaria, due to the development and prevalence of multidrug resistant falciparum malaria (White, 2004).

1.3 Prevalence of Epilepsy

Epilepsy is a chronic neurological disorder of periodic and unpredictable seizures (provoked and unprovoked) from abnormal excessive episodic electrical activity in the brain. It is characterized by signs and symptoms such as convulsion and loss of consciousness (McNamara, 2006; Blume et al., 2001).

It accounts for 0.5% of the global burden of diseases with close to 80% of the cases worldwide found in developing regions (WHO, 2012). It occurs in all ages but most commonly in children and the elderly. Epilepsy is a non-communicable disease and was previously known as “Falling Sickness” (WHO Factsheets, 2009). Most patients with this disease suffer migraine, anxiety, hyperactivity disorder, infertility, serious injuries and suicide-related behaviours with depression (Walczak et al., 2001; Pliophys et al., 2007). People with epilepsy have more days off work, low self-esteem and poor academic performance (Scott et al., 2001). The social stigmatization surrounding epilepsy is often more difficult to overcome than the seizure itself (WHO Factsheets, 2009). The treatment of epilepsy is based on neuroprotection to reduce seizure duration (recovery) and suppress its occurrence (onset) (Arzimanoglou et al., 2002). Many plant-based drugs have been used traditionally in the management of epilepsy of which only a limited number have been evaluated for their potential effects on the central nervous system including epilepsy (Arzimanoglou et al., 2002).

The clinical effectiveness, minimal side effect profiles and relatively low cost of herbal drugs are the reasons for their various applications in traditional medicine (Valiathan, 1998). Their use in modern medicine need to be established by scientifically justifying their validation.

1.4 Statement of Research Problems

Epileptic seizures may lead to serious injuries and suicide-related behaviours with depression thus there is need for medical intervention (Walczak et al, 2004; Pliophys et al., 2007). The WHO estimated in 2006 that neurological disorder and their direct consequences affect as many as one billion people in the world and identified health inequalities and social stigma or discrimination as major factors contributing to the associated disability and suffering. Currently available antiepileptic drugs are confronted with problems such as, pharmacoresistance in approximately 30% of epileptic patients (Sander, 2004), as well as toxicity and serious side effects. In addition, continuous medication is necessary even after the seizures have long been suppressed. In view of these drawbacks, most Epileptologists agree on the need for more selective and less toxic antiepileptic drugs.

1.5 Justification of the Study

About 50 million people in the world have epilepsy (WHO Factsheets, 2009).and about one-third of them are not being adequately managed with the currently available antiepileptic drugs because of non-compliance as a result of long-term therapy, unwanted side effects, high cost and even unavailability of these drugs (McNamara, 2006).

Approximately 80% of the World inhabitants rely on traditional medicine for their primary health care and plants play important role in healthcare system (Cragg et al., 1999). Plants which are readily available and naturally eaten as food could be used in the treatment of epilepsy. WHO encourages the inclusion of herbal medicine of proven safety and efficacy in health care problems of developing Countries (Amos et al., 2001). Scientific research is therefore needed to provide evidence of the safety and efficacy of beneficial medicinal plants. Epilepsy is the most common non neurological public health issue especially in developing African countries. As many as 9 out of 10 people in Africa go untreated (WHO, 2012). This treatment gap greatly increases the burden of epilepsy and disability.

Antiepileptic drugs are expensive and beyond the reach of the common man in Nigeria and other African countries. The scientific investigations of the anticonvulsant activity of the root bark extract of Uvaria chamae will confirm or otherwise disprove its traditional

1.6  Aim and objectives of the Study

1.6.1 Aim

The aim of this research work is to establish the phytochemical constituents present in the root bark of U. chamae, to isolate some compounds using chromatographic techniques and determine the anticonvulsant activities the crude methanol extract (CME) of the plants root bark.

1.6.2 Objectives

1. To carryout preliminary phytochemical screening on the CME root bark of chamae.
2. To screen for the anticonvulsant activity of chamae crude methanol extract (CME).

• To isolate some of the compounds through chromatographic techniques.

1. To characterize the isolated compounds using spectroscopic techniques.

1.7    Research Hypothesis

The CME of the root bark of U. chamae has phytochemical constituents that have anticonvulsant activity

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