Psammaplysin Derivatives from the Balinese Marine Sponge Aplysinella strongylata

Twenty-one new psammaplysin derivatives (4-24) exhibiting a variety of side chains, as well as six previously known psammaplysins, were identified from the Indonesian marine sponge Aplysinella strongylata. The double bond on the side chain of the fatty acid-containing psammaplysins was located by GC-MS analysis of the fatty acid methyl esters and their pyrrolidide derivatives. HPLC and Mosher ester studies confirmed that the isolated metabolites possessing a 19-OH substituent were mixtures of diastereomers. Selected compounds (4, 5, 7, 8, 12, 18, and 22) were screened for in vitro activity against chloroquine-sensitive (3D7) P. falciparum malaria parasites. Of the new psammaplysins, 19-hydroxypsammaplysin E (4) showed the best antimalarial activity, with an IC50 value of 6.4 mu M.