Suberitine A–D, Four New Cytotoxic Dimeric Aaptamine Alkaloids from the Marine Sponge <i>Aaptos suberitoides</i>

Abstract

Suberitine A–D (<b>1</b>–<b>4</b>), four new bis-aaptamine alkaloids with two aaptamine skeleton units, 8,9,9-trimethoxy-9<i>H</i>-benzo[<i>de</i>][1,6]-naphthyridine and demethyl(oxy)-aaptamine, linked through a rare C-3–C-3′ or C-3–C-6′ <b>σ</b>-bond between the 1,6-naphthyridine rings, together with two known monomers <b>5</b> and <b>6</b>, were isolated from the marine sponge <i>Aaptos suberitoides</i>. Their structures were elucidated using NMR spectroscopy. Compounds <b>2</b> and <b>4</b> showed potent cytotoxicity against P388 cell lines, with IC₅₀ values of 1.8 and 3.5 μM, respectively