New diterpene alkaloids from the marine sponge Agelas mauritiana

Chemical investigation of an ethanol extract of the sponge Agelas mauritiana led to the isolation and characterization of five new diterpene alkaloids, namely, (-)-8′-oxo-agelasine B (1), (+)-agelasine B (2), (+)-8′-oxo-agelasine C (3), agelasine V (4), and (+)-8′-oxo-agelasine E (5), along with two known compounds, (-)-8′-oxo-agelasine D (6), and agelasine D (7). The structures of these compounds were determined by interpretation of spectroscopic data and comparison with literature properties. Compounds 1 and 3-5 are the second example of 8′-oxo-agelasine analogs. Compounds 2 and 7 not only exhibited moderate cytotoxicity toward the cancer cell lines PC9, A549, HepG2, MCF-7, and U937 with IC₅₀ values of 4.49-14.41 μM, but also showed potent antibacterial activities against a panel of methicillin-resistant Staphylococcus aureus (MRSA) clinical isolates with MIC₉₀ values of 1-8 μg mL^-1.