Exiguaquinol: A Novel Pentacyclic Hydroquinone from Neopetrosia exigua that Inhibits Helicobacter pylori MurI

Bioassay-guided fractionation of the methanol extract of the Australian sponge Neopetrosia exigua led to the isolation of exiguaquinol (<b>2</b>), a new pentacyclic hydroquinone that inhibited Helicobacter pylori glutamate racemase (MurI) with an IC<sub>50</sub> of 4.4 µM. Its structure and relative configuration were assigned on the basis of spectroscopic data. Exiguaquinol (<b>2</b>), bearing a novel pentacyclic ring skeleton, is the first natural product to show inhibition of H. pylori MurI. Its protein−ligand modeling is also discussed.