Fungi are a group of microorganisms that produce structurally diverse secondary metabolites with various biological activities. Some fungal secondary metabolites have made a mark in history because of their usefulness as drugs, including the penicillins, the statins, and the ergot alkaloids, among others.
Relationships among fungi can sometimes provide an indication about their potential roles as producers of secondary metabolites. Mycoparasitic fungi, for example, attack and parasitize other fungi, eventually causing damage to the host that appears to be inflicted at least in part by antifungal compounds. This observation has inspired our research group to investigate fungal isolates that were obtained as colonists of others in the environment. Some of these colonists were obtained from polypores while others were from basidiomata of mushrooms such as Trametes hirsutum and Earliella scabrosa. These structures are good practical sources of fungal colonists for such studies, since they are ubiquitous in nature, long-lived, and easy to collect.
Chemical studies of one such species, the Botryotrichum state of Chaetomium piluliferum, yielded seven new compounds. Five of these are polyketide-derived, while the other two are of mixed amino acid and polyketide origin. The crude organic extract of Coniothyrium palmarum yielded five new cleistanthane and pimarane-type diterpenoids of which one showed good antifungal activity. An Acremonium species that was obtained from the same source as the culture of C. palmarum yielded three new decanolides that are polyketide in origin. An unidentified Verticillium species produces a particularly diverse set of secondary metabolites, including two new cyclodepsipeptides. Another as-yet unidentified fungal species yielded a polyester and eremophilane-type sesquiterpenes, together with a known decanolide that was also isolated from the Acremonium species.
The new compounds were characterized by extensive 1D and 2D NMR analysis as well as mass spectrometry. Relative configurations were proposed on the basis of NOESY data and/or X-ray crystallographic analysis, while absolute configurations were determined by CD spectral analysis, chiral HPLC of amino acid residues from hydrolysis products, and/or other chemical derivatizations methods.
Some of the compounds isolated show biological activities, including antifungal, antibacterial, and antiinsectan effects.