Synthesis, characterization, and pharmacological evaluation of new GABA analogs as potent anticonvulsant agents

A series of new gamma-aminobutyric acid (GABA) derivatives was obtained from 4-(1,3-dioxoisoindolin-2-yl)butanoic acid by coupling it with various substituted amines by using DCC as coupling reagent. The compound 3 was synthesized by treating GABA and phthalimide at high temperature under anhydrous conditions. All the synthesized compounds were confirmed and characterized by using various spectral technique like (IR, H-1 NMR, C-13 NMR, and mass spectroscopy) studies. Anticonvulsant evaluations of all the synthesized compounds were done by using various seizures models like maximal electroshock-induced seizure (MES), subcutaneous pentylenetetrazole (scPTZ), subcutaneous strychnine (scSTY), and intraperitoneal picrotoxin (ipPIC)-induced seizure threshold tests at a dose of 30, 100, and 300 mg/kg body weight and anticonvulsant activity was noted at 0.5 and 4 h time intervals after the drug administration. The compound 4a 4-(1,3-dioxoisoindolin-2-yl)-N-phenylbutanamide displayed weak anticonvulsant activity in MES test at a dose of 300 mg/kg. Analogs 4d, 4h, and 4m displayed promising activity in scPTZ seizures model. Most of the synthesized compounds were found to be effective in the scSTY and ipPIC models and very few compounds showed protection in the scPTZ model. Among all the tested compounds, 4h 4-(1,3-dioxoisoindolin-2-yl)-N-(4-ethylphenyl)butanamide showed protection in various seizures model except in the scSTY model, while analog 4d was found to be the most potent compound in scPTZ model showing protection at a dose of 30 mg/kg. Further all the compounds exhibited lesser neurotoxicity compared with standard drug. The essential structural features responsible for interaction with receptor site are established within a suggested pharmacophore.