Lehualides E−K, Cytotoxic Metabolites from the Tongan Marine Sponge Plakortis sp.

Spectroscopy-guided chemical analysis of a marine sponge from the genus Plakortis, collected in Tonga, yielded seven new metabolites of polyketide origin, lehualides E−K (5−11), four of which incorporate various sulfur functionalities. The structures of compounds 5−11 were elucidated by interpretation of spectroscopic data and spectral comparison with model compounds. The biological activities of compounds 6−9 were investigated against human promyeloid leukemic HL-60 cells and two yeast strains, wild-type and a drug-sensitive mutant.