Rhabdastrenones A–D from the sponge Rhabdastrella globostellata

Abstract

Three new isomalabaricanes (1–3), a new α-pyrone derivative (4), together with four known isomalabaricane analogs rhabdastrellin G (5), isogeoditin A (6), stelliferin A (7), and (13E)-isogeoditin A (8) were isolated from the marine sponge Rhabdastrella globostellata. Their chemical structures were determined by HR-ESI-MS, 1D and 2D-NMR spectroscopic data analysis. The absolute configurations were identified by Mo₂(OAc)₄ induced ECD spectra and TD-DFT theoretical calculated ECD spectra. Compound 6 exhibited weak cytotoxic effects against HepG2 and SKMel2 cell lines with the IC₅₀ values of 7.53 ± 0.70 and 9.93 ± 0.95 μM, respectively.