6'-Hydroxy-3'-methoxy-mitorubrin, a new potentiator of antifungal miconazole activity, produced by Penicillium radicum FKI-3765-2.

A new mitorubrin congener designated 6'-hydroxy-3'-methoxy-mitorubrin (1) was isolated along with structurally related 4'-hydroxy-3'-methoxy-(S)-mitorubrin (2) and monomethyl-(S)-mitorubrin (3) from the culture broth of Penicillium radicum FKI-3765-2 by solvent extraction, octadecyl silyl (ODS) column chromatography and HPLC. The structure of 1 was elucidated by various spectral analyses, including NMR experiments. They have a common isochromane-like ring with a similar hydrophobic side chain. These compounds moderately potentiated miconazole activity against Candida albicans.