New Imidazole Alkaloid and Glycerol Metabolites from the TonganMarine Sponge Leucetta sp.

A chemical investigation into the organic extract from a Tongan marine sponge of the genus Leucetta, guided by Nuclear Magnetic Resonance (NMR) spectroscopy, resulted in the isolation of 20 compounds. The structures of all isolated metabolites were established through comprehensive analysis using extensive NMR and mass spectrometric (MS) techniques. Two new compounds were identified: naamidine L (1), an imidazole alkaloid, and a glycerolipid (2). In addition to these new structures, 18 known metabolites were also isolated. A majority of the isolated compounds were subsequently evaluated for cytotoxicity against the human HL-60 leukemia cancer cell line. The known imidazole alkaloid naamidine A (3) displayed significant potency with an IC₅₀ value of 6.1 µM, while the newly discovered naamidine L (1) was ineffective at concentrations below 22 µM. Two known 5α,8α-epidioxy sterols were the strongest antiproliferative agents among the isolates, exhibiting potent activity with IC50 values of 0.6 µM and 2.0 µM. These findings highlight the potential of metabolites derived from Leucetta sponges as potent antiproliferative agents for further biomedical research.