Neuromodulatory Steroid Metabolites From the Sponge <i>Topsentia</i> sp.

Two steroids (1, 2) and four steroid sulfates (3-6) were isolated from the sponge Topsentia sp. collected from the South China Sea. The structures of these compounds were determined based on spectroscopic methods and comparison with reported data. Compound 5 was reported for the first time from the title sponge. Compounds 4 and 5 concentration-dependently inhibited spontaneous synchronized Ca²⁺ oscillations (SCOs) and 4-aminopyridine (4-AP) -induced epileptic discharges in primary cultured cortical neuronal networks. Interestingly, compound 5 promoted SCOs at concentrations below 1 µM and inhibited SCOs at concentrations above 3 µM. The compound also inhibited 4-AP-induced SCOs' hyperactivity. This is the first report of steroid sulfates for their SCOs' inhibitory activity, showing potential as an antiepileptic agent. The chemotaxonomic significance of the isolated compounds was also discussed.