ABSTRACT
The marine sponge Lamellodysidea herbacea is one of the marine organisms containing unique organobromine molecules polybrominated diphenyl ethers (PBDEs) which have diverse biological activities. Compounds 1−4 have been successfully isolated and their structures were elucidated using nuclear magnetic resonance (NMR) spectroscopy, single-crystal x-ray diffraction, and comparison with data in literature. Compound 1, C12H6 O4 Br6 , was isolated in gram quantity (1.35 g) and elucidated as 2,3,4,5-tetrabromo-6-(3ʹ,5ʹ-dibromo-2ʹ-hydroxyphenoxy)phenol after NMR and X-ray analysis. Compound 1 takes a twist-like conformation with torsion angle ϕ1 = 27.7 (6)°; ϕ2 = 86.5 (5)°, while the angle of the ether bond is 117.5°. Compounds 2−4 were elucidated as 2,3,5-tribromo-6-(3ʹ,5ʹdibromo-2ʹ-hydroxyphenoxy)anisole, 2,3,5-tribromo-6-(3ʹ,5ʹ-dibromomethoxyphenoxy) phenol, 2,3,5-tribromo-6- (3ʹ,5ʹ-hydroxyphenoxy)phenol, respectively. Antibacterial evaluation of 1−4 on Gram-positive and Gram-negative pathogens showed that the potent activity was at 0.08 µg/disk, 12 ± 0 mm (Staphylococcus aureus ATCC 6538); 6.25 µg/disk, 10 ± 0 mm (Klebsiella pneumoniae); and 50 µg/disk, 12 ± 0 mm (ampicillin-resistant Escherichia coli). Compounds 1, 2, and 4 showed ichthyotoxicity (zebrafish embryos, Danio rerio) at a level of LC50 >10 µg/ml [dead, 48 hours postfertilization (hpf)]. This is the first report that compound 4 inhibits the growth of antibiotic-resistant bacteria.