Caelestines A−D, Brominated Quinolinecarboxylic Acids from the Australian Ascidian <i>Aplidium caelestis</i>

Four new brominated natural products, caelestines A−D (<b>1</b>−<b>4</b>), have been isolated from the Australian ascidian <i>Aplidium caelestis</i>. The structures of <b>1</b>−<b>4</b> were determined by analysis of their NMR and MS data. This is the first report of brominated quinolinecarboxylic acids from nature. Compound <b>1</b> has been previously synthesized but not spectroscopically characterized. Compounds <b>1</b>−<b>4</b> were tested against three mammalian cell lines (MCF-7, NFF, and MM96L) and a panel of microbial strains and showed only minor cytotoxicity.