Synthesis and evaluation of anticonvulsant activities of 7‐phenyl‐4,5,6,7‐tetrahydrothieno[3,2‐b]pyridine derivatives

A series of 7-phenyl-4,5,6,7-tetrahydrothieno[3,2-b]pyridine derivatives containing triazole and other heterocycle substituents (methyltriazole, tetrazole, and triazolone) is described. Two experimental methods, maximal electroshock (MES) and subcutaneous pentylenetetrazole (scPTZ), were used to evaluate the anticonvulsant activity of the target compounds. Moreover, the neurotoxicity (NT) was tested using the Rotarod test. 5-(4-Chlorophenyl)-4,5-dihydrothieno[2,3-e][1,2,4]triazolo[4,3-a]pyridine (6c) showed the best anticonvulsant activity. In the MES and PTZ experiments, the 50% effective dose (ED₅₀ ) values of compound 6c were 9.5 and 20.5 mg/kg, respectively. From the therapeutic index (PI) values, 6c (MES and PTZ with PI values of 48.0 and 22.2, respectively) showed better safety than the clinical drugs carbamazepine (MES with PI value of 6.4) and ethosuximide (PTZ with PI value of 3.2). The biological activities of the compounds were verified by using molecular docking studies. Compound 6c showed significant interactions with residues at the benzodiazepine-binding site on gamma-aminobutyric acid A (GABA_A ) receptors. The results of in vivo GABA estimation and bicuculline-induced seizures showed that 6c may have an effect on the GABA system. The physicochemical and pharmacokinetic properties of the target compounds were predicted.