Structure and Antibacterial Activity of Brominated Diterpenes from the Red Alga Sphaerococcus coronopifolius

Four new tetracyclic brominated diterpenes, 1-4, were isolated from the organic extract of Sphaerococcus coronopifolius, collected from the rocky coasts of Corfu Island. The structures of the new natural products, as well as their relative configurations, were elucidated on the basis of extensive spectral analyses, including 2D-NMR experiments. The isolated metabolites were evaluated for their antibacterial activity against a panel of bacteria including multidrug-resistant (MDR) and methicillin-resistant Staphylococcus aureus (MRSA) with MIC values in the range of 16-128 mu g/ml.