Scalarane Sesterterpenoids Isolated from the Marine Sponge Hyrtios erectus and their Cytotoxicity against HeLa and MCF-7 Cancer Cells

Abstract

Eighteen scalarane sesterterpenoids (1–18), including eight new derivatives (1–8), were isolated from the sponge Hyrtios erectus (family Thorectidae), the extract of which showed cytotoxicity against the HeLa and MCF-7 cell lines. Of the new derivatives, six compounds (1–6) were found to contain a γ-hydroxybutenolide moiety capable of reversible stereoinversion at the hydroxylated carbon center. Under the influence of other adjacent functional groups, each derivative exhibited a different stereochemical behavior, which was fully deduced by ROESY experiments. All the iso-lated compounds were examined for their cytotoxicity, and they were found to show weak growth inhibitory activities against HeLa and MCF-7 cancer cells. The compounds containing a γ-hydroxybutenolide moiety (1–3, 10, 12) showed cytotoxicity with IC50 values ranging from 24.3 to 29.9 μΜ), and the most potent derivative was heteronemin (16, IC50 20.0 μΜ).