(-)-Mycousnine is a microbial metabolite of usnic acid produced by the strain of M. nawae that has antibacterial and antifungal activities. It is active against the Gram-positive bacteria B. subtilis, K. rhizophila, and S. aureus (MICs = 4, 8, and 4 g/ml, respectively). (-)-Mycousnine is also active against the fungi T. mentagrophytes, T. rubrum, and C. albicans (MICs = 25, 25, and 100 µg/ml, respectively).