Dihydroisocoumarin derivatives with antifouling activities from a gorgonian-derived Eurotium sp. fungus

Abstract

Five pairs of new dihydroisocoumarin enantiomers, (±)-eurotiumides A–E, and two related racemates, (±)-eurotiumides F and G, were isolated from a gorgonian-derived fungus, Eurotium sp. XS-200900E6. The enantiomeric separations for (±)-eurotiumides A–E were achieved by chiral-HPLC, and their absolute configurations were determined by ECD spectra. All of the isolated compounds are rare dihydroisocoumarin derivatives with a methoxy at C-4. (+)- And (−)-eurotiumides B and D with cis configurations of H-3/H-4 exhibited potent antifouling activities against the larval settlement of the barnacle Balanus amphitrite with the EC50 values ranging from 0.7 to 2.3 μg/mL, and displayed high therapeutic ratios (LC50/EC50 >15). The tested compounds also showed extensive antibacterial activities. It was the first report of antifouling activities for dihydroisocoumarin derivatives.