Oxy-Polybrominated Diphenyl Ethers from the Indonesian Marine Sponge, : X-ray, SAR, and Computational Studies.

Polybrominated diphenyl ether (PBDE) compounds, derived from marine organisms, originate from symbiosis between marine sponges and cyanobacteria or bacteria. PBDEs have broad biological spectra; therefore, we analyzed structure and activity relationships of PBDEs to determine their potential as anticancer or antibacterial lead structures, through reactions and computational studies. Six known PBDEs (-) were isolated from the sponge, ; C NMR data for compound are reported for the first time and their assignments are confirmed by their theoretical C NMR chemical shifts (RMSE < 4.0 ppm). Methylation and acetylation of (2, 3, 4, 5-tetrabromo-6-(3', 5'-dibromo-2'-hydroxyphenoxy) phenol) at the phenol functional group gave seven molecules (-), of which , , and were new. New crystal structures for and are also reported. Debromination carried out on produced nine compounds (, , , -, , and ) of which was new. Debromination product showed a significant IC 8.65 ± 1.11; 8.11 ± 1.43 µM against human embryonic kidney (HEK293T) cells. Compounds and exhibited antibacterial activity against Gram-positive and Gram-negative with MID 0.078 µg/disk. The number of four bromine atoms and two phenol functional groups are important for antibacterial activity ( and ) and cytotoxicity (HEK293T). The result was supported by analysis of frontier molecular orbitals (FMOs). We also propose possible products of acetylation and debromination using analysis of FMOs and electrostatic charges and we confirm the experimental result.