Xanthoradones, new potentiators of imipenem activity against methicillin-resistant Staphylococcus aureus, produced by Penicillium radicum FKI-3765-2: I. Taxonomy, fermentation, isolation and biological properties

The fungal strain FKI-3765-2, identified as Penicillium radicum, was found to produce potentiators of imipenem activity against methicillin-resistant Staphylococcus aureus (MRSA). Two new compounds, designated xanthoradones A and B, were isolated from the fermentation broth of the producing strain by solvent extraction, octadecyl silyl column chromatography and preparative HPLC. Xanthoradones A and B potentiated imipenem activity against MRSA by decreasing the MIC value of imipenem from 16 mu g ml(-1) to 0.060 and 0.030 mu g ml(-1), respectively. The Journal Antibiotics (2009) 62, 431-434; doi: 10.1038/ja.2009.69; published online 24 July 2009