The targets of antifungal antibiotics in clinical use are more limited than those of antibacterial antibiotics. Therefore, new antifungal antibiotics with different mechanisms of action are desired. In the course of our screening for antifungal antibiotics of microbial origins, new antifungal antibiotics, simplifungin (1) and valsafungins A (2) and B (3), were isolated from cultures of the fungal strains Simplicillium minatense FKI-4981 and Valsaceae sp. FKH-53, respectively. The structures of 1 to 3 including their absolute stereochemistries were elucidated using various spectral analyses including NMR and collision-induced dissociation (CID)-MS/MS as well as chemical approaches including modifications to the Mosher's method. They were structurally related to myriocin. They inhibited the growth of yeast-like and zygomycetous fungi with MICs ranging between 0.125 and 8.0 μg/mL. An examination of their mechanisms of action by the newly established assay using LC-MS revealed that 1 and 2 inhibited serine palmitoyltransferase activity, which is involved in sphingolipid biosynthesis, with IC50 values of 224 and 24 nM, respectively.

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A new antioxidant, designated pyranonigrin L, was isolated from the culture materials of the hot spring-derived fungus Penicillium adametzii BF-0003 by solvent extraction, ODS column chromatography, and HPLC. Its planar structure was elucidated using various analytical techniques including UV, IR, and NMR spectroscopy and MS. Its absolute configuration was determined by a comparison of its circular dichroism (CD) spectrum with those of structurally related compounds. Pyranonigrin L was found to exhibit anti-oxidative activity with an EC 50 value of 553 µM.

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