Study On The Biosynthetic Potential And Bioactivity Of The Secondary Metabolites Of The Endophytic Fungus Emericella Sp. Associated With Panax Notoginseseng

Endophytes are one of the most important sources of microbial natural drugs.Attract extensive attention from researchers because of their novel structure and rich activity.The research work divided into three parts:Separation of endophytic fungus associated with Panax pseudoginseng,the target strains with research value were selected by antimicrobial activity screening;Use"OSMAC"and chemical epigenetic modification strategies for this target strain to excavate biosynthetic potential;Study on bioactivity of monomer compounds isolated from target strains.17 strains of endophytic fungi were isolated from fresh Panax notoginseng plants by tissue surface disinfection.The 18S rDNA sequences of the endophytic fungi were identified,and the metabolites of the endophytic fungus were screened for their antimicrobial activity.The results showed that the fungus Emericella sp.XL-029 has a significant antimicrobial activity,so this active strain was used as the research object for the next step.This section uses the“OSMAC”strategy and chemical epigenetic modification strategies to tap the biosynthetic potential of the active target strain.Firstly,using the"OSMAC"strategy to change the culture mode and the composition of the medium.As a result,it was found that the metabolites of the solid rice glucose medium and the liquid MEB medium were more abundant in fermentation.Then use these two kinds of culture medium to expand fermentation culture and extract metabolites.The metabolites were separated and purified by means of classical column chromatography and semi-preparation HPLC.The structures of the monomer compounds were analyzed by spectroscopic techniques such as NMR,IR,UV,MS and X-ray single crystal diffraction.Finally,14 monomer compounds,including 6 new compounds,were identified from their solid expanded fermentation metabolites.12 compounds,including 3 new compounds were isolated and identified from the liquid metabolite MEB expansion metabolites.Next,we screened the chemically epigenetic modifications of the Emericella sp.XL-029.Due to poor screening results,no further expansion cultures were performed.Finally,we conducted a screening test on the anti-human pathogenic bacteria,anti-phytopathogenic fungi,and anti-tumor activity of some of the isolated monomeric compounds.Antibacterial activity screening revealed that compound 10 has a significant inhibitory activity against B.cereus（MIC 6.3μg/mL）;anti-phytopathogenic fungi screen found that compound 10 against V.dahliae Kleb and H.maydis had significant inhibitory activity（MIC 6.3μg/ml and 3.1μg/mL）;antitumor activity screening showed that compound 4 has a strong selective inhibitory activity against highly metastatic hepatoma cell lines(IC₅₀ 9.8μM)and good inhibitory effect on their migration,invasion and adhesion.