Antibacterial Polyketide Heterodimers from Pyrenacantha kaurabassana Tubers

Two heterodimers comprising anthraquinone and methylbenzoisocoumarin moieties (1 and 2) were isolated, together with emodin and physcion from the tubers of Pyrenacantha kaurabassana. The structures of 1 and 2 were established by NMR spectroscopy, including the analysis of a 2D INADEQUATE spectrum. On the basis of the data obtained, the structures that were previously proposed in the literature for these compounds were revised. Compounds 1 and 2 showed antibacterial activity against three different strains of Staphylococcus aureus. Compound 2 also showed bactericidal activity against Helicobacter pylori.