Chemical Investigations Of Two Strains Of Wetland Derived Fungi

Fungi are as the second largest biologicial group,with a conservative estimation of over one and a half million species,but less than 6% have been described,and much less have been chemically investigated.Fungal secondary metabolites are one of the most important sources of new drugs or lead compounds.A notable example is penicillin,which was discovered about 100 years ago,has played a pivotal role in fighting bacterial infections.Other examples include the cholesterol-lowing agent lovastatin,immunosuppressant cyclosporine A,and the anti-multiple sclerosis drug fingolimod.However,it has become increasingly difficult to find new secondary metabolites,largely due to the facts that the often studied microorganisms are usually common soil fungi,which are easily to collect and culture.On the other hand,those fungal species from unique habitats are more likely to produce structurally unique and biologically active secondary metabolites,since that have gradually evolved special strategies(metabolic systems)to adapt to the environments,or to interact to other organisms.These fungal species include entomogenous,endophytic,psychrotolerant,and marine fungi,which are ideal sources of lead compounds in drug discovery.The wetland fungi refer to those species that inhabit in the shallow water areas with stationary or flowing bodies of water,such as natural or artificial swamps,and the areas of water depths of less than 6 meters at low tide,which remained largely un-explored in terms of secondary metabolites.The wetland ecosystem harbors various biological groups including fungi,and its multiple functions are important to maintain the ecosystems.The wetland fungi are important components of the wetland microbial environment,and possess huge potential in the production of bioactive secondary metabolites.Chemical investigations of the wetland fungi have primarily focused on those isolated from mangrove forests,implying that the wetland fungi have been largely ignored in chemical studies.In this study,the fungal species isolated from the wetland environments were first cultured in small scale to prepare the crude extracts.After HPLC finger-printing and antimicrobial testing,two fungal strains,Paraconiothyrium sporulosum and Pycnidiophora dispersa,were selected,and the selected organisms were further grown in different fermentation cultures and conditions in larger scale to compare the crude extracts,which were analysed by HPLC and HPLC–MS,based on which the optimal conditions were selected for culturing.After separation and purification,a total of 34 compounds were obtained,11 of which were new metabolites.The structures of the new compounds were elucidated using a combination of mass spectrometry(MS),nuclear magnetic resonance(NMR),circular dichroism(CD),and X-ray diffraction analysis.Some of the compounds obtained in this work were evaluated for their activities against a panel of bacteria and human tumor cell lines.Chemicla investigations of the wetland fungi are still limited,the preliminary results from this study implied that wetland fungi were valuable resources for the discovery of new bioactive secondary metabolites,which may be served as lead compounds for further evaluation.