Stemphones, novel potentiators of imipenem activity against methicillin-resistant Staphylococcus aureus, produced by Aspergillus sp FKI-2136

A fungal strain FKI-2136 identified as genus Aspergillus was found to produce potentiators of imipenem activity against methicillin-resistant Staphylococcus aureus (MRSA). Two new compounds designated stemphones B and C were isolated along with a structurally related known compound cochlioquinone D from the fermentation broth of the producing strain by solvent extraction, silica gel column chromatography and preparative HPLC. These compounds have a common tetracyclic quinone skeleton. Stemphone C potentiated imipenem activity against the MRSA 512 told by decreasing MIC value of imipenem from 16 mu g/ml to 0.03 mu g/ml.