Gombamide A, a Cyclic Thiopeptide from the Sponge Clathria gombawuiensis

A new peptide, gombamide A (1), was isolated from the marine sponge Clathria gombawuiensis, collected from Korean waters. On the basis of the results of combined spectroscopic analyses, the structure of this compound was determined to be a cyclic C-terminally modified thiohexapeptide containing the unusual amino acid residues para-hydroxystyrylamide (pHSA) and pyroglutamic acid (pyroGlu). The absolute configurations of all amino acid residues were determined to be L by advanced Marfey's analysis. The new compound exhibited weak cytotoxicity against A549 and K562 cell lines as well as moderate inhibitory activity against Na+/K+-ATPase.