Synthesis of Novel Indolylbenzothiazepines/ Indolylbenzoxaziepines Substituted 2-Oxo/Thiobarbituric acids as Potential Anticonvulsant Agents

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INTROdUCTION
Epilepsy is a disorder related to the nervous system affecting the brain and its activity by causing frequent seizures and sometimes, loss of awareness.In simple words, epilepsy is a disorder or disease of the brain with a potential of making a human unconscious.A group of medicative agents that are used for the treatment of epilepsy are referred to as anticonvulsant agents.Although a large number of anticonvulsant drugs are present and are being used for the treatment of epileptic seizures, yet their long exposure can lead to drug resistance.In addition, the presently available drugs are also associated with severe side effects such as hypnosis, sedation, etc. thereby retarding everyday performance.As per epidemiological studies [1][2][3] , currently the disease affects more than 60 million people worldwide.Thus, a novel and a safer anticonvulsant drug is the most needed scientific discovery of today.
Mephobarbital 4 and phenobarbital 5 , which are derivatives of 2,4,6-tri-oxo-hexahydropyrimidine (barbituric acid) are medically being used for the treatment of epilepsy.The substitution with various alkyl, aryl or heteroaryl moieties at fifth position of barbituric acid [6][7][8][9] and thiobarbituric acid [9][10][11][12] was found to plays an essential role in modulating the antiepileptic effect.Indoles [13][14][15][16][17] have been found to possess antiepileptic activity in maximal electroshock seizure model experiment.Literature survey reveals that derivatives of benzothiazepines as well as benzo-oxazepines were used in the synthesis and design of new and different antiepileptic drugs.The chemistry and pharmacology of benzothiazepine and benzoxazepine derivatives have been of substantial attraction to health professionals for the reason that their by-products were found to possess various biotic activities such as antiinflammatory 18 , antimicrobial [18][19] , antioxidant 20 , antitumor 21 , antipsychotic [22][23] , anticonvulsant [23][24][25][26] , etc.In view of above discussion the motive of this study is to synthesize newer antiepileptic drugs by embodying benzothiazepine and benzoxazepine segments on 2-oxo/thiobarbituric acids (at fifth position) which was already incorporated with indole moiety.The introduction of these components on 2-oxo/thiobarbituric acids (at fifth position), may be innovative as the substituted groups themselves possess anticonvulsant effect and their introduction on 2-oxo/thiobarbituric acids (at fifth position) was further expected to enhance the antiepileptic activity.

Chemistry
Melting points were recorded with the help of thermonic melting point apparatus.The open capillary tubes were used for taking the melting points which were faulty (not correct).The homogeneousness and pureness of the drugs produced were examined using TLC (thin layer chromatography) utilizing plates of silica gel-G.Methanol-benzene mixture in the ratio of 2:8 was used as an eluent.The spots of TLC were located with the help of iodine.Carlo Erba 1108 analyzer was used to perform elemental analysis (C, H, N) and were found within the range of ±0.04% of the conceptual values.Perkin Elmer 881 FT-IR spectrophotometer (ν max in cm -1 ) was used to record IR spectra.Bruker DRX-300-FTNMR instrument was used to record 1 H-NMR spectra in CDCl 3 .
Compounds (1-14) were synthesized according to the routes depicted in Fig. 1.The physical data (melting points, recrystallization solvents, yields, molecular weights, elemental analysis) of derivatives (1-14) is stated in Table 1.These synthesized drugs (1-14) were also evaluated for their antiepileptic activeness and also for their ALD 50 (acute toxicity).The standard drug used for antiepileptic activity was phenytoin sodium.The results of biological activity that is antiepileptic acitivty and acute toxicity is depicted in (Table 2).

Synthesis General procedure to synthesize 5-methoxy-2thio/ oxo barbituric acids (1-2)
To 2-thio/oxobarbituric acid (20 g), acetyl chloride (50 mL) was add on little by little with regularly moving the liquid round and round and maintaining the temperature between 0-5 0 C. Magnetic stirrer was used to stir the reaction mixture for another 10 hours.After stirring the mixture was kept overnight.Distillation assembly was used to distill off excess of acetic acid.The solid residue obtained after distillation was washed with water again and again and was then poured into ice.Filtration pump was used to filter the solid residue.The solid residue thus obtained was filtered which was again solidified using suitable solvents.The analytical as well as physical details of compounds 1-2 is stated in Table 1.Compound 1: 1 H-NMR CDCl 3 δ: 5.80 (s, 1H, CHCOCH 3 ), 2.55 (s, 3H, COCH 3 ), 9.20 (s, 2H, 2N-HC=O).IR (cm -1 , KBr): 1740, 1720, 1690, 1700 (C=O), 3180 (-N-H).

Pharmacology Anticonvulsant activity
Supra maximal electroshock seizure pattern test (SMES) model was used for screening antiepileptic activity.Method of Tomen et al., 27 was utilized for this model.Albino rats having weight ranging between 90-120 g of either sex were put to use for test.The rats were splited into groups.Groups were made in such a way that each group of rats contains ten animals.Test drugs as well as the standard drug-phenytoin sodium were injected intraperitoneally (i.p.) in rats.After 1 h of drug administration, the rats were put through a shock of 150 milliampere via ear electrodes for 0.2 seconds.The absence or presence of extensor response in the rats was duly observed.Rats (animals) in which extensor reciprocation was put to end were taken as secured rats.

Acute Toxicity (ALd 50 )
The acute toxicity studies were carried out in mice.All the compounds which were prepared were scrutinized for acute toxicity (ALD 50 ) in mice.This test was done by using the plan opf action given by Smith 28 .

Anticonvulsant activity in rats
All the compounds (1-30) synthesized were studied for their antiepileptic activity.The novel compounds were synthesized according the routes depicted in Fig. 1.The compounds were tested for their biological activity i.e. antiepileptic test at a dose of 30 mg/kg i.p. against SMES experimental model (supra maximal electroshock induced seizures).The compounds 1-30 showed substantive activity varying between 40% to 90%.Out of thirty compounds evaluated, compounds 9, 20 and 28 exhibit excellent protection against convulsions thereby providing 80%, 90% and 80% protection against convulsions, correspondingly.The outcome of antiepileptic test are stated in Table 2.

CONCLUSION
If we consider the anticonvulsant activity observed in all the newly synthesized compounds, it may concluded that: 1.