Modulation of polyketide biosynthetic pathway of the endophytic fungus, sp. FL0768, by copper (II) and anacardic acid.

In an attempt to explore the biosynthetic potential of endosymbiotic fungi, the secondary metabolite profiles of the endophytic fungus, sp. FL0768, cultured under a variety of conditions were investigated. In potato dextrose broth (PDB) medium, sp. FL0768 produced the heptaketides, herbaridine A (), herbarin (), 1-hydroxydehydroherbarin (), scorpinone (), and the methylated hexaketide 9,11-(+)-ascosalitoxin (). Incorporation of commonly used epigenetic modifiers, 5-azacytidine and suberoylanilide hydroxamic acid, into the PDB culture medium of this fungus had no effect on its secondary metabolite profile. However, the histone acetyl transferase inhibitor, anacardic acid, slightly affected the metabolite profile affording scorpinone () as the major metabolite together with 1-hydroxydehydroherbarin () and a different methylated hexaketide, ascochitine (). Intriguingly, incorporaion of Cu into the PDB medium enhanced production of metabolites and drastically affected the biosynthetic pathway resulting in the production of pentaketide dimers, palmarumycin CE (), palmarumycin CP (), and palmarumycin CP (), in addition to ascochitine (). The structure of the new metabolite was established with the help of spectroscopic data and by MnO oxidation to the known pentaketide dimer, palmarumycin CP (). Biosynthetic pathways to some metabolites in sp. FL0768 are presented and possible effects of AA and Cu on these pathways are discussed.