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 (511), four of which incorporate various sulfur functionalities. The structures of compounds 511 were elucidated by interpretation of spectroscopic data and spectral comparison with model compounds. The biological activities of compounds 69 were investigated against human promyeloid leukemic HL-60 cells and two yeast strains, wild-type and a drug-sensitive mutant.