New bioactive halenaquinone derivatives from South Pacific marine sponges of the genus Xestospongia.

Bioassay-directed fractionation of South Pacific marine sponges of the genus Xestospongia has led to the isolation of a number of halenaquinone-type polyketides, including two new derivatives named xestosaprol C methylacetal 7 and orhalquinone 8. Chemical characterization of these two new compounds was achieved by extensive 1D and 2D NMR spectroscopic studies. Evaluation of anti-phospholipase A(2), anti-farnesyltransferase and antiplasmodial activities of this series is presented and structure/activity relationships are discussed. Orhalquinone 8 displayed a significant inhibition of both human and yeast farnesyltransferase enzymes, with IC(50) value of 0.40 microM and was a moderate growth inhibitor of Plasmodium falciparum.