Synthesis and characterization of new 5,5′-dimethyl- and 5,5′-diphenylhydantoin-conjugated hemorphin derivatives designed as potential anticonvulsant agents

Abstract

Herein, the synthesis and characterization of some novel N-modified hybrid analogues of hemorphins containing a C-5 substituted hydantoin residue as potential anticonvulsants and for the blockade of sodium channels are presented. Their structure–property relationships are highlighted by electrochemical and Fourier transform infrared spectroscopy (FT-IR) analysis methods. The lipophilicity and molecular docking of voltage-gated sodium channels were also determined. The new series of 5,5′-dimethyl- and 5,5′-diphenylhydantoin-conjugated hemorphin derivatives were obtained as C-terminal amides via solid-phase peptide synthesis, an Fmoc-strategy using 2-(1H-benzotriazole-1-yl)-1,1,3,3-tetramethylaminium tetrafluoroborate (TBTU). The anticonvulsant activity of the hybrid-peptides (0.25, 0.5 and 1 μg) was tested by maximal electroshock (MES) and 6 Hz psychomotor seizure tests using male ICR mice. None of the compounds tested showed neurotoxicity in the rotarod test. The reference drug phenytoin was used as a positive control. The most active compound Ph-5 showed 100% efficacy against the 6 Hz-induced psychomotor seizures at a dose of 1.0 μg and tonic seizures in the MES test at a lower dose of 0.5 μg. This analogue of VV-hemorphin-5 contained a 5,5′-diphenylhydantoin residue at the N-terminus and a hydrophobic Val–Val–Tyr–Pro–Trp–Thr–Gln–CONH₂ amino acid sequence of the peptide molecule. The quantitative data for the 6 Hz test demonstrated that the peptide Ph-5 exhibited a median effective dose (ED50) value of 0.358 μg and PI >13.97, and ED50 of 0.25 μg and PI >20.35 in the MES test, respectively. Results from the docking study suggest that the neuropeptide Ph-5 is a potent inhibitor of sodium channels, and blockade of voltage-gated sodium channels could be the mechanism of action of the hybrid-peptide derivatives with anticonvulsant activity.