Chemical Investigation Of One Strain Of Endolichenic Fungus

The number of fungi species is conservatively estimated at1.5million, secondonly to insects. But only6%are known, and much less have been chemicallyinvestigated, therefore taking possession of huge potential in the discovery of newbioactive natural products. Natural products have been demonstrated to play animportant role in discovery of lead compounds for therapeutics, and fungi are one ofthe most important sources of bioactive natural products. Many important medicineshave been discovered or derived from fungal secondary metabolites, such as thepenicillin as antibiotics, lovastatin as an anti-cholesteremic agent, cyclosporin A as animmuno-suppressive agent. Endophytic fungi are microorganisms that live in normaltissues of the hosts without causing apparent syntoms. The relationship between anendophyte and its host may range from latent phytopathogenesis to mutualisticsymbiosis. In recent years, due to redundant discovery of the known compoundsfrom other sources, fungi have attracted more attention as the producers of newbioactive natural products.In this study, one strain of endolichenic fungi collected in Zixi Mountain ofYunnan Province, People’s Republic of China, were selected for chemical studies.The crude extracts prepared from solid-substrate fermentation cultures werefractionated by column chromatography and reversed-phase high performance liquidchromatography (HPLC) using various stationary and mobile phases. A total of16second metabolites were isolated from the extract and11of which are new ones.The structures of the new compounds were elucidated by nuclear magneticresonance (NMR), mass spectrometry (MS), in combination with circular dichroism(CD) and chemical degradations and derivatizations. The isolated new compoundswere tested against a panel of bacteria, fungi, the plant pathogenic fungi. Themajority of these new metabolites showed unconspicuous activities.Results from chemical studies of the selected strain of endolichenic fungi haveafforded a variety of new bioactive metabolites, and some of them possessunique structural features. These preliminary results implied that the endophytic fungi, especially the unique and chemically under-explored endolichenic speciescould be another important source of bioactive natural products, and warrant furtherchemical investigations to explore their metabolic potential.