Discovery of a Novel Antiepileptic Bicyclic Norditerpenoid from the Marine Algae-Derived Fungus Chloridium sp. NBU3282

Two antiepileptic metabolites, nordichloridene (1) and 9-chloro-1,2,3,4-tetrahydroacridine (2), were isolated from the marine algae-derived fungus Chloridium sp. NBU3282. Nordichloridene (1) is a new norditerpenoid featuring a bicyclic 6/6 trans-decalin skeleton conjugated with an α,β-unsaturated methyl vinyl ketone side chain. Its structure was elucidated via comprehensive spectroscopic analysis, and the stereochemical configuration was established by NOESY spectroscopy combined with quantum chemical calculations. Compound 2, previously known only in synthetic chemistry, was identified from a natural source for the first time. Both compounds suppressed pentylenetetrazole-induced hyperactivity in a zebrafish epilepsy model, demonstrating antiepileptic potential via acetylcholinesterase activation and the modulation of epilepsy-associated genes.