SYNTHESIS AND ANTICONVULSANT STUDIES OF 3 ISOMERS OF 4-[(DIMETHYLPHENYL)AMINO]-4-OXOBUTENOIC ACID

ABSTRACT

Epilepsy is a disorder of public concern worldwide and has been widely treated via pharmacotherapy, which are faced with challenges such as cost of therapy, side effects, toxicity and lack of selectivity. As such, researchers agree on the need to identify more selective, readily available and lesser toxic anti-epileptic drugs. Three isomeric forms was synthesized using equimolar amount of furan-2,5-dione and 2,4-; 2,5- and 2,6- dimethyl isomers of aniline via a nucleophile-electrophile addition reaction at a temperature of 700C and refluxed. The compounds A, B and C were synthesized with good yields of 87, 85 and 80 % respectively and melting points of 105, 75 and 900C respectively. The structures were elucidated using spectroscopic techniques, particularly 1D and 2D NMR. Acute toxicity studies were carried out using Lorke’s method while neurotoxicity was assessed using the beam walk assay. The compounds were screened for anticonvulsant activity using Maximum Electro-Shock Test (MEST) and subcutaneous Pentelenetetrazole (scPTZ) induced seizure test. Compound A, B and C has a median lethal dose of 774.6, 1131.4, and 1131.4 mg/kg respectively. In the neurotoxicity test, the compounds B and C showed no falls when tested against diazepam 1.5mg/kg (40 falls) showing it was not neurotoxic at test doses. In the MES test distilled water 2 ml/kg exhibited a mean time of recovery of 8.3 minutes with 0% protection while the Phenytion 20mg/kg recovered in 2 mins with a 80% protection. Compound A shows a 0% protection and mean time of recovery of 14.7, 10.2 and 10.4 minutes at test dose of 50, 100 and 200mg/kg. Compound B at test doses of 75, 150 and 300 mg/kg showed 0% protection and mean time of recovery of 5.9, 5.2 and 6.5 minutes respectively at all test doses. Compound C at test doses of 75, 150 and 300 mg/kg showed a mean time of recovery of 7.7, 5.8 and 5.8 minutes respectively with a 20% protection at all test doses. Therefore, compound B and C has activity gainst MEST by decreasing the mean time of recovery from seizure. In the scPTZ test, the distilled water 2ml/kg ip and compound A, B and C showed no protection likewise, no increase in onset against scPTZ induced seizure. Therefore compound A, B and C shows no activity against scPTZ induced seizure. The 3 isomers were synthesized with good yields, characterised, and found to be 4-[(2, 4- dimethylphenyl) amino]-4-oxobutenoic acid (A), 4-[(2, 5-dimethylphenyl) amino]-4-oxobutenoic acid (B) and 4-[(2, 6- dimethylphenyl) amino]-4-oxobutenoic acid (C). They were not neurotoxic and showed no significant quantal protection at test doses but reduced the mean time of recovery from seizure in the MES test. No significant activity was observed in the scPTZ test.

CHAPTER ONE

1.0 INTRODUCTION

1.1 Background

Epilepsy is a chronic disorder of the brain that affects people in every country of the world. It is characterized by recurrent seizures from episodic discharge. Seizures are brief episodes of involuntary shaking which may involve a part of the body (partial) or the entire body (generalized) and sometimes accompanied by loss of consciousness and control of bowel or bladder function. (WHO, 2016)

Brain cells communicate with each other and other cells through electrical signals. Seizure occurs when there is excessive electrical discharge from a group of brain cells (WHO 2016).

There is no recognized cause of epilepsy, although it may develop following a brain damage caused by infection, tumor, trauma or other kinds of neurological defects and diseases (Rang et al., 2007).

Over 50 million people have been estimated to have epilepsy in the world of which about 75% or more are in developing countries and underdeveloped countries with little or no access to proper medical services (Meinardi et al., 2001; Ngugi et al., 2010; WHO 2016).

Communication and coordination of the entire body is partly by the nervous system which consists of the brain the spinal cord. This system is consisting of millions of microcellular unit called the neuron (a nerve cell). This neuron as seen in figure 1.1 consists of a cell body, an axon (branch) and dendrites which connect one neuron to another at a junction called the synapses by communication of electrical signals across channels in the nerve cell membrane (Shield et al., 2000)