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.