Neuropharmacological evaluation of hydralazine hydrazone derivatives: Synthesis, In silico, and zebrafish studies

Hydralazine is an old antihypertensive drug that, through drug repurposing strategies, has shown significant potential as a therapeutic agent for other diseases. Additionally, it presents itself as a promising precursor for the synthesis of new compounds. This study evaluates the anxiolytic, anticonvulsant, and memory-retention potential of hydralazine and its hydrazone derivatives (HDZH 2,4OH, HDZH 3,4,5OCH₃, and HDZH CNM) in adult zebrafish. The compounds were synthesized with yields of 60 %, 55 %, and 48 %, respectively, and showed no toxicity after 96 h. In behavioral tests, the compounds reduced locomotor activity and induced anxiolytic effects at doses of 4 and 40 mg/kg (hydralazine), 20 mg/kg (HDZH CNM), and 40 mg/kg (HDZH 2,4OH and HDZH 3,4,5OCH₃). These effects were reversed by flumazenil and serotonergic antagonists, indicating action on GABA_A and 5-HT receptors. Hydralazine, HDZH 2,4OH, and HDZH 3,4,5OCH₃ also preserved memory in inhibitory avoidance tests. Molecular docking simulations indicated that the derivatives bind to the GABA_A receptor at the same allosteric site as the DZP agonist, with HDZH 3,4,5OCH₃ standing out for sharing hydrophobic interactions with Tyr58 and Tyr210 and forming a strong hydrogen bond with His102. Consistently, pharmacokinetic predictions indicated a better profile for HDZH 3,4,5OCH₃, showing a good balance between absorption and central nervous system penetration. The results highlight the potential of hydralazine and its derivatives as neuropharmacological candidates, supporting their repurposing and the development of new drugs.