Abstract
Entomopathogenic fungi infect insects through the cuticle, grow as hyphal bodies or hyphae in the hemocoel, and cause host death by nutritional destruction of tissues, and producint toxic metabolites and pathogenic enzymes. To date, entomopathogenic fungi have not been extensively studied by natural product chemists. We focused on entomopathogenic fungi as new resources for biologically active compounds, and studied the diversity of their secondary metabolites. In this study, we show the isolation and structure elucidation of novel pyrone diterpene-type compounds, metarhizin A-H (1-8) from Metarhizium flavoviride, and their antiproliferative activities on human cancer cell lines. Additionally, we synthesized many metarhizin derivatives, evaluated their antiproliferative activities, and discuss the structural requirements for this activity. A novel pyrone diterpene-type compound, Nf-1 (9), was also isolated from Nectria flammea. Oomycetes from fungus-like mycelium and were calssified as fungi in the past. However, the cell walls of them are c omposed of cellulose rather than chitin, as in the fungi. In the present, the ultrastructure, biochemistry and molecular sequences of them indicate that the oomycetes belong to the Kingdom Chromista, not the Kingdom Fungi. We also focused on oomycetes as new resources for natural product chemistry. A new oxidized lanostane-type compound, St-1 (23), was isolated from the mycelium of oomycete Saprolegnia terrestris. The structure of 23 was determined by spectral means including EIMS, and ^1H and ^<13>C NMR.
