Exploiting the secondary metabolome of tropical Basidiomycota

Only 1-2% of the known species of the phylum Basidiomycota have been studied intensively for secondary metabolite production, while presumably over 90% have not even been cultured in the laboratory. Their great capability to produce unique antibiotics and other secondary metabolites is exemplified by strobilurins and pleuromutilins, both of which gave rise to highly successful products. In the past three years, we have studied cultures of Basidiomycota from Thailand and Kenya for production of novel metabolites, relying on extensive field work, phylogenetic pre-selection methods, state-of-the-art methods for fermentation, downstream processing and structure elucidation. These projects have resulted in the discovery of several novel bioactive compounds from rare and new species, using a bioassay-guided isolation procedure.

Specifically, novel cyathane-pyridine terpene alkaloids were isolated from a Cyathus species collected in Thailand, and additional novel cyathanes named latitextins were obtained from a culture of Latitextum collected in Kenya. Novel cyathanes and other terpenoids were isolated from the well-known medicinal mushrooms Hericium coralloides and H. erinaceus. A new species of the pleurotoid genus Hohenbuehelia sp., which readily produces fruitbodies and can trap nematodes in culture, yielded various novel pleurotin derivatives. Novel cuparenic-mevalonic acid conjugates were found from a new species of the genus Deconica. Moreover, chlorinated gymnopalynes A and B with an acetylenyl side chain were isolated from a new Gymnopus species.

The isolation and structure elucidation, as well as the biological activities of the aforementioned and additional novel compounds will be presented.