The Preliminary Study Of Secondary Metabolites From Symbiotic Fungi Of Aspergillus Sp.IFB-YXS

Natural products is closely connected with drugs of human being especially traditional medicine.The clinical,pharmacology study of drugs from natural products and chemical research is the cornerstone of the discovery of many traditional medicines.We preliminarily studyed the bioactive natural products from endophyte of Aspergillus sp.IFB-YXS,mainly consists of the following work:The first chapter is a mini-review concerning progress of natural products and endophytes.In the second chapter,the antimicrobial compounds were characterized with bioassay-guided method from the ethanol extract derived from the solid-substrate fermentation of Aspergillus sp.IFB-YXS,an endophytic fungus residing in the apparently healthy leave of Ginkgo biloba L.The aim of this work was to evaluate the antimicrobial activity and mechanism(s)of these bioactive compounds against phytopathogens.Among the compounds,xanthoascin(1)is significantly inhibitory on the growth of the phytopathogenic bacterium Clavibacter michiganense subsp.Sepedonicus with a minimum inhibitory concentration(MIC)value of 0.31 ?g/ml,which is more potent than streptomycin(MIC 0.62 ?g/ml),an antimicrobial drug co-assayed herein as a positive reference.Moreover,terphenyl derivatives 3,5 and 6 are also found to be active against other phytopathogens including Xanthomonas oryzae pv.oryzae Swings,Xanthomonas oryzae pv.oryzicola Swings,Erwinia Amylovora and Pseudomonas syringae pv.Lachrymans etc.The antibacterial mechanism of xanthoascin(1)was addressed to change the cellular permeability of the phytopathogens,leading to the remarkable leakage of nucleic acids out of the cytomembrane.The work highlights the possibility that xanthoascin(1),an analogue of xanthocillin which is used to be an approved antibiotic,may find its renewed application as a potent antibacterial agrichemical.This study contributes to the development of new antimicrobial drugs,especially against C.michiganense subsp.Sepedonicus.In the third chapter,we studyed the cytotoxicity and anti-inflammatory activity of the natural products from endophyte of Aspergillus sp.IFB-YXS.