The marine sponge Lamellodysidea herbacea is one of marine organisms containing unique organobromine molecules PBDEs which have diversed biological activities. Compounds 1−4 have been successfully isolated and elucidated their structures using NMR spectroscopy, single crystal x-ray diffraction, and comparison with those data in literatures. Compound 1, C12H6O4Br6, was isolated in gram quantity (1.35 g) and elucidated as 2,3,4,5-tetrabromo-6-(3',5'-dibromo-2'-hydroxyphenoxy)phenol after NMR and X-ray analysis. Compound 1 takes a twist-like conformation with torsion angle 1 = 27.7 (6) ; 2 = 86.5 (5), while the angle of the ether bond is 117.5°. Compounds 2−4 were elucidated as 2,3,5-tribromo-6-(3',5'-dibromo-2'-hydroxyphenoxy)anisole, 2,3,5-tribromo-6-(3',5'-dibromomethoxyphenoxy) phenol, 2,3,5-tribromo-6-(3',5'-hydroxyphenoxy)phenol, respectively. Antibacterial evaluation of 1−4 on gram-positive and gram-negative pathogens showed that the potent activity was at 0.08 g/disk, 12 ± 0 mm (S. aureus ATCC 6538); 6.25 g/disk, 10 ± 0 mm (K. pneumoniae); 50 g/disk, 12 ± 0 mm (ampicillin resistant E. coli). Compounds 1, 2, and 4 showed ichthyotoxicity (zebrafish embryos, D. rerio) at a level of LC50 >10 g/mL (dead, 48 hpf). This is the first report that compound 4 inhibits the antibiotic-resistant bacteria.
Key words: PBDE, Lamellodysidea herbacea, NMR, X-ray crystallography, antibiotic resistance
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