Cytotoxic Phyllactone Analogs from the Marine Sponge Phyllospongia papyrecea

Background: A growing evidence indicates that marine sponge Phyllospongia sp. is one of rich sources of 20, 24-bishomoscalarane sesterterpenes with potent biological activities. In order to search more bioactive 20, 24-bishomoscalarane sesterterpenes for new drug discovery, chemical investigation was carried out on an Indonesian marine sponge P. papyrecea. Methods: Bioassay-guided fractionation was carried out on its dichloromethane extract. And nine compounds were purified and isolated using HPLC. Their chemical structures were determined by a combination of spectroscopic and spectrometric data, including 1D-, 2D-NMR and HRESI-MS. Their cytotoxic activities were performed on three human tumor cell lines A549, MCF-7 and HeLa using the CCK-8 method. Results: One new 20, 24-bishomoscalarane sesterterpene, phyllactone H (9), was isolated and elucidated together with phyllactones A-B (1-2) and D-G (3-6), 12, 24-dihydroxy-20, 24-dimethyl-15, 17-scalaradien-25, 24-olides (7-8). Compounds 1 and 2, 3 and 4, 5 and 6, 7 and 8 were C-24 anomers and inseparable mixtures, respectively. The 1 H and 13 C-NMR data for 7/8 were firstly reported in this paper. Conclusion: Compounds 1-9 possessed in vitro moderate cytotoxicities against A549, MCF-7 and HeLa cells with IC50 values of less than 25 mu M.