N-Propynyl analogs of β-phenylethylidenehydrazines: Synthesis and evaluation of effects on glycine, GABA, and monoamine oxidase

A group of β-phenylethylidenehydrazines possessing a variety of substituents (Me, OMe, Cl, F, and CF3) at the ortho-, meta-, or para-positions of the phenyl ring, in conjunction with either a N-bis-(2-propynyl) or a N-mono-(2-propynyl) moiety, were synthesized and compared to the novel neuroprotective drug β-phenylethylidenehydrazine (PEH) with regard to their ability to inhibit the enzymes GABA-transaminase (GABA-T) and monoamine oxidase (MAO)-A and -B in vitro in brain tissue. Two of the analogs synthesized (mono- and bis-N-propynylPEH) were also studied exvivo in rats to compare their effects to those of PEH with regard to ability to inhibit GABA-T and MAO and to change brain levels of several important amino acids. Unlike PEH, none of the new drugs inhibited GABA-T in vitro at 10 or 100 μM, and all of the drugs (including PEH) were poor inhibitors (at 10 μM) of MAO-A and -B invitro. The two analogs studied exvivo inhibited GABA-T to a lesser extent than PEH, unlike PEH that did not elevate brain levels of GABA, and inhibited MAO-A and -B more potently than PEH. Interestingly, unlike PEH, the two analogs caused marked increases in brain levels of glycine; because of the current interest in drugs that increase glycine availability in the brain as potential antipsychotic drugs, these two analogs now warrant further investigation.

Analogs of β-phenylethylidenehydrazine (PEH) were synthesized and screened in vitro. 7p (R1H, R2CH2CCH, R3CH2CCH) and 8p (R1H, R2H, R3CH2CCH) were tested ex vivo for effects on rat brain levels of amino acids (above) and enzyme activity.Figure optionsDownload as PowerPoint slide