Inhibition of Seizure-Like Paroxysms and Toxicity Effects of Securidaca longepedunculata Extracts and Constituents in Zebrafish Danio rerio

Plants used in traditional medicine in the management of epilepsy could potentially yield novel drug compounds with antiepileptic properties. The medicinal plant Securidaca longepedunculata is widely used in traditional medicine in the African continent, and epilepsy is among several indications. Limited knowledge is available on its toxicity and medicinal effects, such as anticonvulsant activities. This study explores the potential in vivo inhibition of seizure-like paroxysms and toxicity effects of dichloromethane (DCM) and ethanol (EtOH) extracts, as well as isolated xanthones and benzoates of S. longepedunculata. Ten phenolic compounds were isolated from the DCM extract. All of the substances were identified by nuclear magnetic resonance spectroscopy. Assays for toxicity and inhibition of pentylenetetrazole (PTZ)-induced seizure-like paroxysms were performed in zebrafish larvae. Among the compounds assessed in the assay for maximum tolerated concentration (MTC), benzyl-2-hydroxy-6-methoxy-benzoate (MTC 12.5 μM), 4,8-dihydroxy-1,2,3,5,6-pentamethoxyxanthone (MTC 25 μM), and 1,7-dihydroxy-4-methoxyxanthone (MTC 6.25 μM) were the most toxic. The DCM extract, 1,7-dihydroxy-4-methoxyxanthone and 2-hydroxy-1,7-dimethoxyxanthone displayed the most significant inhibition of paroxysms by altering the locomotor behavior in GABAA receptor antagonist, PTZ, which induced seizures in larval zebrafish. The EtOH extract, benzyl benzoate, and benzyl-2-hydroxy-6-methoxy-benzoate unexpectedly increased locomotor activity in treated larval zebrafish and decreased locomotor activity in nontreated larval zebrafish, seemingly due to paradoxical excitation. The results reveal promising medicinal activities of this plant, contributing to our understanding of its use as an antiepileptic drug. It also shows us the presence of potentially new lead compounds for future drug development.