(-)-Mycousnine is a microbial metabolite and derivative of usnic acid originally isolated from M. nawae that has antibacterial and antifungal activities.1,2 It is active against the Gram-positive bacteria B. subtilis, K. rhizophila, and S. aureus (MICs = 4, 8, and 4 g/ml, respectively) but not the Gram-negative bacteria E. coli, S. typhimurium, and K. pneumoniae (MICs = >128 g/ml for all).2 (-)-Mycousnine is also active against the fungi T. mentagrophytes, T. rubrum, and C. albicans (MICs = 25, 25, and 100 µg/ml, respectively).1
1.Sassa, T., and Igarashi, M.Structures of (-)-mycousnine, (+)-isomycousnine and (+)-oxymycousnine, new usnic acid derivatives from phytopathogenic Mycosphaerella nawaeAgric. BioI. Chem.54(9)2231-2237(1990) 2.Lee, J., Lee, J., Kim, G.J., et al.Mycousfurans A and B, antibacterial usnic acid congeners from the fungus Mycosphaerella sp., isolated from a marine sedimentMar. Drugs17(7)422(2019)