Study On The Secondary Metabolites Of Two Plant Endophytic Fungi And Four Plant Pathogenic Fungi

Bioactive natural products play an important role in research and development of new drugs.Fungi distribute widely in nature,and the number of conservatively estimated species is about 1.5 million,but with only 70,000 known species.Fungi possess ecological,biological,and genetic diversities,inhabiting various biotopes with different living strategies.The biodiversity of fungi in taxonomy and the biotopes in which they inhabit leads to the production of a variety of secondary metabolites that display a broad range of bioactivities,from which some very important medicines have been discovered,such as the antibiotics penicillin,the anti-cholesteremic agent lovastatin,immuno-suppressant cyclosporin A,the antifungal agents echinocandins,and gilenya for the treatment of multiple sclerosis.Thus,fungi possess tremendous promise in discovery of novel lead compounds with therapeutic potential.In this work,six strains of selected terrestrial fungi were grown in a solid-substrate fermentation cultures.The prepared EtO Ac extracts were subsequently fractionated by silica gel and/or Sephadex LH-20 column chromatography,and reversed-phase high performance liquid chromatography(RP HPLC)to afford 48 compounds,19 of which were new metabolites.The structures of the new compounds were elucidated primarily by nuclear magnetic resonance(NMR),mass spectrometry(MS),circular dichroism(CD)and chemical degradation and derivatizations.The new compounds obtained in this work were evaluated for their activities against a panel of bacteria,fungi,and the plant pathogenic fungi,as well as human tumor cell lines.The results from chemical studies of the selected six strains of fungi have resulted in the discovery of a variety of bioactive metabolites,many of them possess unique structural features and significant antimicrobial and cytotoxic effects.The percentage of new metabolites discovered through this study has been unusually high(40%),largely due to the selection of unique fungi for investigations.These new metabolites not only provide candidates for the discovery of bioactive lead compounds,but also provide insights into the living strategy of the niche groups.