Phytochemical and Anticonvulsant Studies on Methanol Extract of the Root Bark of Uvaria Chama EP. Beauv. (Annonaceae)

Phytochemical and Anticonvulsant Studies on Methanol Extract of the Root Bark of Uvaria Chama EP. Beauv. (Annonaceae)

ABSTRACT

Uvariachamae P. Beauv. (Annonaceae) is widely distributed in Africa, the plant species are used in traditional medicine as an anti-inflammatory, antimalarial, and analgesic. It is also used for the treatment of jaundice, epilepsy, and microbial infections. The powdered root bark of U.chamaewas extracted with methanol using the maceration method and the resulting crude methanol extract (CME) was solvent fractionated to give hexane (HF), chloroform (CF), ethyl acetate (EF), and n-Butanol (BF) fractions. The chloroform fraction was step-wisely eluted in a silica gel-packed column to afford eleven fractions S1-S12. 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 tests and spectroscopic techniques (UV and 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 meantime of recovery from seizures in MEST compared to the 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 a dose of 30mg/kg protected 80% of mice against pentylenetetrazole and significantly (P˂ 0.05) delayed the onset of a 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 has demonstrated anticonvulsant activity and may be useful in the treatment of generalized absence seizures.

CHAPTER ONE

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 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 leads 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 narcotic analgesic from Papaver somniferum served as a lead compound to the synthesis of naloxone and buprenorphine; (vii) Cocaine: from Erythroxylon coca leaves served as a lead for more potent and less toxic local anesthetics 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 sesquiterpene lactone isolated from the plant Artemisia annua and its semi-synthetic derivatives are such as, artemether (iii), arteether (iv), artesunate (v) are a 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).

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 behaviors 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 needs to be established by scientifically justifying their validation.

1.4 Statement of Research Problems

Epileptic seizures may lead to serious injuries and suicide-related behaviors with depression thus there is a 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 pharmacoresistant 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.

Given 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’s inhabitants rely on traditional medicine for their primary health care and plants play important role in the healthcare system (Cragg et al., 1999). Plants that 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 nonneurological 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 use.

1.6 Aim and objectives of the Study

1.6.1 Aim

This research work aims to establish the phytochemical constituents present in the root bark of U. chamae, isolate some compounds using chromatographic techniques and determine the anticonvulsant activities of the crude methanol extract (CME) of the plant’s root bark.

1.6.2 Objectives

i) To carry out preliminary phytochemical screening on the CME root bark of U.chamae.

ii) To screen for the anticonvulsant activity of U. chamae crude methanol extract (CME).

iii) To isolate some of the compounds through chromatographic techniques.

iv) 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.