Petrosamine B, an Inhibitor of the Helicobacter pylori Enzyme Aspartyl Semialdehyde Dehydrogenase from the Australian Sponge Oceanapia sp.

Bioassay-guided fractionation of the MeOH extract of the sponge Oceanapia sp. using the Helicobacter pylori enzyme, aspartyl semialdehyde dehydrogenase, ASD, to detect antibacterial activity, led to the isolation of a new pyridoacridine alkaloid, petrosamine B (<BO>1</BO>). Petrosamine B is a bright blue compound that is sparingly soluble in many organic solvents. The structure of <BO>1</BO> was determined from detailed NMR studies performed in TFA/D<INF>2</INF>O. Petrosamine B was found to be a weak inhibitor of ASD with an IC<INF>50</INF> of 306 μM.