Screening strategies for obtaining novel, biologically active, fungal secondary metabolites from marine habitats

To determine the best sources of novel, biologically active metabolites, both endophytic fungi (plant isolates) and fungi associated with algae were isolated from plants and algae from marine habitats of the North, Baltic and Mediterranean Seas, Atlantic Ocean, and Gulf of Mexico. Following preselection of the isolates according to taxon and metabolic profiles, almost all were active in at least one of the tests for antibacterial, antifungal, and/or herbicidal activities. Metabolites isolated from the culture extracts belonged to diverse structural groups; 42% were previously unknown structures. Compared to fungi associated with algae, endophytic fungi were a better source of novel metabolites and antifungal culture extracts; they produced a higher number of metabolites per fungus. Microsphaeropsis spp. and Coniothyrium spp. synthesized the highest numbers of novel metabolites per isolate, and Geniculosporium, Nodulisporium and Phomopsis the greatest numbers of metabolites per isolate. Based on the proportion of novel to known metabolites, endophytic fungi from marine environments equalled endophytes from terrestrial habitats. Metabolic profiles (HPLC-DAD) of the saprophytic, marine fungi belonging to Dendryphiella spp. from diverse temperate and subtropical locations revealed that geographical source of the isolates had little qualitative effect on secondary metabolite production in this genus.