| Natural products with rich skeleton diversity usually show some biological activity and play a highly significant role in the drug discovery and development process. By far, about 80% of drugs were either natural products or analogs inspired by them. Due to the expansion of new techniques and the challenges and obstacles faced by natural products chemistry, natural products become less important. However, natural products are still the major source of drug development.It has been increasingly difficult to identify new bioactive compounds from common microbiology resources. Microbiology from special habitats usually produce abundant natural products scaffold for survival in environments threatening growth or to combat competing life forms. There is a long-term evolution and complex process of interaction between the plant pathogenic fungi and plant. With unique living environment, plant pathogenic fungi produce the natural products, usually with good biological activity, to play a very crucial role in the ecological defense system.In the thesis, four plant pathogenic fungi (Ulocladium sp. isolated from Everniastrum sp., Bipolaris sp. from plant disease spot, Fusarium oxyporum from the matrix of Antrodia camphor ate) were cultured under different fermentation conditions to prepare the organic solvent extracts through the OSMAC strategy. Based on bioassay results, TLC and HPLC analysis, the optimal culture conditions were chosen to do large-scale fermentation. Pure compound were obtained from crude extract by silica gel column chromatography (CC), Sephadex LH-20 CC, ODS CC and RP HPLC and their structures were elucidated by 1 D,2 D NMR, MS and CD. From the Ulocladium sp. thirty-six compounds (1-36) are identified, including ten ophiobolins (1-10), thirteen tricycloalternarenes (13-25), nine polyketides (11,26,27,29-33,36) and four benzene derivatives (12,28,34,35). The Bipolaris sp. afford nine compounds (37-45), including four ophiobolins (37-39,45) and five cochlioquinones (40-44). From F. oxyporum eleven compounds (46-56) are obtained, including pyrone derivatives, peptides, glycosides, and steroid and benzene derivatives.All isolated compounds were evaluated their anti-microbial and anti-tumor activity. Ophiobolins (1-10,37-39) show strong cytotoxic activity, and are first reported their anti-BCG activity. Compounds 5 and 37 exhibited anti-BCG activity with the MIC values of 11.94 and 12.5 ?g/mL, respectively. To explain the mechanism of compound 37 in inducing the apoptosis, the down-regulated expression of c-Myc was observed after 3 hours of treatment, and the expression of Bcl-2 was down-regulated after 4 hours treatment. It was also evidenced that the expression of Bcl-XL remained unchanged. Compound 37 can result in the autophagy of HeLa, indicating that there is an important regulatory mechanism for compound 37 in autophagy or mitochondrial autophagy.Through the OSMAC strategy we researched the secondary metabolites of four plant pathogenic fungi and got 56 compounds with special skeleton and diverse activities. It proved that OSMAC method is a simple method to maximize the diversity of microbial natural products and that plant pathogenic fungi are the important source of natural products. |
PDF Full Text Request