A new cyclic heptapeptide, ectyoplasin (1), was isolated from a methanol extract of the sponge Ectyoplasia ferox. The planar structure of 1, cyclo(-Leu1-Asn2-Ala3-Val4-Thr5-Pro6-Gly7-), was determined by one and two-dimensional NMR spectroscopy and high-resolution tandem mass spectrometry. Its absolute stereochemistry was solved by Marfey's method. The in vitro assays show that ectyoplasin (1) possess significant cytotoxic activity (2.9 - 23.5 µM) against the cell lines, DU-145 (human prostate cancer), Jurkat (human T-cell acute leukaemia), MM144 (human multiple myeloma), HeLa (human cervical carcinoma) and CADO-ES1 (human Ewing's sarcoma). The DU-145 cell line showed apoptotic cell death in response to ectyoplasin (1) treatment.
Keywords: Cyclic heptapeptide; Ectyoplasia ferox; cytotoxic activity; five cell lines.