Engyodontochones, Antibiotic Polyketides from the Marine Fungus Engyodontium album Strain LF069

Abstract

Six new (2, 4-8) and two known polyketides with a basic structure of an anthraquinone-xanthone were isolated from mycelia and culture broth of the fungus Engyodontium album strain LF069. The structures and relative configurations of these compounds were established by spectroscopic means, and their absolute configurations were defined mainly by comparison of quantum chemical TDDFT calculated and experimental ECD spectra. Compounds 2 and 4-8 were given the trivial names engyodontochone A (2) and B-F (4-8). Compounds 5-8 represent the first example of a 23,28 seco-beticolin carbon skeleton. The relative and absolute configurations of two known substances JBIR-97/98 (1) and JBIR-99 (3) were determined for the first time. All isolated compounds were subjected to bioactivity assays. Compounds 1-4 exhibited inhibitory activity against methicillin-resistant Staphylococcus aureus (MRSA) that was 10-fold stronger than chloramphenicol.

Keywords: antibiotics; drug discovery; natural products; polyketides; structure elucidation.