New Bioactive Metabolites Produced By Endophytic Fungi

Because of the interaction with the host, symbiotic fungi produced diverse secondary metabolites which played an important role for themselves and the host in the process of co-evolution. Since Fleming made the great discovery of penicillin from microorganism in 1929, we gradually realized that the metabolites can not only be used as anti-microbe agents, but also well-behaved in many fields, especially in the discoveried of immunological regulators, enzyme inhibitors, antimetabolites and anti-tumor agents. Therefore, the study of microbial secondary metabolites not only allows us to discover more novel compounds with new structures, but also helps to explore more pharmacologically active compounds.This dissertation reports the structure and bioactivity of secondary metabolites produced by two symbiotic microbes including one fungus Aspergillus versicolor GH-2 obtained from a Tenoderaaridifolia Stoll (carnivorous insect), and an fungal endophyte Myrothecium roridum IFB-E012 isolated from the stem of Artemisia annua L. A total of thirty-three compounds were isolated from the fermentation broth by a combination of chromatographies over silica gel and ODS reverse column, gel filtration over Sephadex LH-20, and semipreparative HPLC. The structures of the new compounds consisting of six prenylated diphenyl ethers and one anthraquinone were elucidated by spectroscopic analyses (HR-ESI-MS, EIMS, IR,1H-NMR, 13C-NMR, HMQC,’H-’H COSY, HMBC, NOESY, ROESY, CD) and X-ray diffractions. Furthermore, these isolated compounds were assayed in vitro for antimicrobial and cytotoxic activities.The mantis-associated fungus Aspergillus versicolor GH-2 has been shown to produce twenty-two compounds, among them seven new compounds, consisted by eleven diphenyl ethers, three xanthones, four anthraquinone derivatives, three phenols and one indoles. In vitro cytotoxic activity assay of these isolates were performed indicating that compound 3 and 4 showed 25.64% and 32.21% cell growth inhibitory activities against MCF-7 at 10μM. Besides, the cell growth inhibitory activity against HeLa of compound 2 was 29.29% at 10 uM. Two known compounds,9 and 12 exhibited significant antibacterial activity against Streptococcus pyogenes, organism that causes respiratory and cutaneous infections, with the MIC value of 2.5 and 5.0 μg/mL, While the MIC valve of positive drug control streptomycin is 0.6 μg/mL.M. roridum IFB-E012 is an endophytic fungus residing in the stem of thetraditional Chinese medicinal plant Artemisia annua (Asteraceae) collected from the coast of the Yangtze River in Nanjing (China). Repeated column chromatographies of the extract from the culture of the fungus led to the isolation of ten macrocyclic trichothecenes and one N-Acetyltryptamine. Compound 32 exhibited significant antibacterial activity against Pyricularia oryzae with the MIC value of 10.0μg/mL, while the MIC valve of positive drug control kanamycin is 2.5 μg/mL, which means the compound 32 showed significant activities against the plant pathogen. In cytotoxicity experiments, the compound 32 also showed good inhibitory activity to BGC823.Symbionts are important source of new active natural products. The new compounds enriched the type of diphenyl ethers found in A. versicolor. The activisty of compounds provided clues for the study of the interaction between endophytes and their hosts. Finally, recent advances concerning the insect-associated fungus and endophytes were reviewed in the thesis.