Cytotoxic psammaplysin analogues from a Suberea sp. marine sponge and the role of the spirooxepinisoxazoline in their activity.

Seventeen bromotyrosine-derived metabolites, including eight new compounds, were isolated from a Micronesian sponge of the genus Suberea. Four of the new compounds were psammaplysin derivatives (10-13), and the other four were ceratinamine derivatives (14-17). Of the compounds obtained, the psammaplysins exhibited cytotoxicity against human cancer cell lines (GI₅₀ values down to 0.8 μM), while the ceratinamine and moloka'iamine analogues showed almost no activity. These results suggest that the spirooxepinisoxazoline ring system is a requirement for cytotoxicity and, therefore, may serve as an attractive molecular scaffold for the development of a potent anticancer agent.