Anticonvulsant activity and selective inhibition of NAD-dependent oxidations by 1,4-disubstituted piperazines

Several 1-(1-aryl-3-ethylthiocarbamido)-4-(arylaminothiocarbonyl)piperazines were synthesized, characterized by their sharp melting points and elemental analyses and evaluated for anticonvulsant activity. All disubstituted piperazines at a dose of 100 mg/kg i.p. provided 10-90% protection against pentylenetetrazol-induced convulsions in mice. These disubstituted piperazines selectively inhibited the in vitro oxidation of nicotinamide adenine dinucleotide (NAD)-dependent oxidation of pyruvate, alpha-ketoglutarate, beta-hydroxybutyrate and NADH by rat brain homogenates. The NAD-independent oxidation of succinate remained unaltered. The anticonvulsant activity possessed by disubstituted piperazines was unrelated with their ability to selectively inhibit respiratory activity of rat brain homogenates. Amongst 1-(substituted benzyl)-4-(substituted benzoyl)piperazines exhibiting central nervous system (1, 2) depressant activity it was found that 1-(2-chlorobenzyl)-4-(2-chlorobenzoyl)piperazine possessed maximum activity (2). The ability of piperazine carbamides (3) and piperazinothiocarbamides to possess anticonvulsant activity (4) prompted synthesis of 1-(1-aryl-3-ethylthiocarbamido)-4-(arylaminothiocarbonyl)piperazines and evaluation of their anticonvulsant activity. The effects of these disubstituted piperazines were also investigated on the in vitro respiratory activity of rat brain homogenates in an attempt to elucidate the biochemical mechanism of action for their anticonvulsant activity.