The Active Secondary Metabolites From Endophytic Fungi And Rhizosphere Microorganisms Associated With Dendrobium SPP.

These endophytes and rhizosphere microorganisms can produce different active metabolties,which were the sources of natural medicines.Dendrobium spp.are famous Chinese medicinal plants,which contain abundant endophytic fungi.The secondary metabolites from endophytic fungi associated with Dendrobium plants can provide new theoretical basis and potential application value for the discovery of novel structural active substances and the research of innovative drugs and pesticides.In this paper,107 strains were isolated from the medicinal plants Dendrobium and these strains belong to 40 genera.Among them,Fusarium sp.,Colletotrichum sp.and Xylaria sp.were the dominant strains.21 rhizosphere microorganisms were isolated from the rhizosphere soil of Dendrobium plants.These strains belong to 13 genera.In this paper,eighty-three compounds,including twenty-three new compounds,were obtained from six endophytic fungi and rhizosphere microorganisms associated with Dendrobium.The structure types of the compounds are polyketide,benzofuran derivative,terpene,steroid,nucleoside,benzene ring derivative and so on.Some of these compounds were evaluated for photodynamic antimicrobial activity,cytotoxic activity,antihyperlipidemic activity,nitric oxide inhibition,glucose uptake stimulating activities,anti-acetylcholinesterase and antifeedant activities against silkworm larvae.Some of the metabolites showed prominent activities.The thesis was divided into seven chapters.In the first chapter,the research progress of antimicrobial substances from endophytic fungi was reviewed,which can provide references for the discovery of new antimicrobial agents from microorganisms.The second chapter was mainly about the endophytes and rhizosphere fungi from the medicinal plants Dendrobium in Xiaojie,Wenshan of Yunnan province.These strains were identified by morphological identification and ITS sequence analysis.The diversity of endophytic fungi from Dendrobium were also discussed.The third chapter was mainly about twenty-three metabolites,including six new compounds,from Daldinia eschscholzi associated with Dendrobium chrysotoxum,named as（R）-2,3-dihydro-2,5-dihydroxyl-2-methylchromen-4-one（1）,（2R,4S）-2,3-dihydro-2-methyl-benzopyran-4,5-diol（2）,（R）-3-methoxyl-1-（2,6-dihydroxyphenyl）-butan-1-one（3）,7-O-?-D-ribosyl-5-hydroxy-2-methyl-4H-chromen-4-one（4）,7-O-?-D-ribosyl-2,3-dihydro-5-hydroxy-2-methyl-4H-chromen-4-one（5）,daldinium A（6）.The structural types of these compounds are polyketide,benzofuran derivative,terpene,steroid and benzene ring derivative.The photoantibacterial activities of some compounds were studied,and the antibacterial activities of orcinotriol（7）against Escherichia coli and 5-methyl-2-vinyltetrahydrofuran-3-ol（9）against Escherichia coli and Bacillus subtilis were significantly enhanced under the light induction.Compound 5 has activity on stimulating glucose-uptaking.The fourth chapter mainly focus on the metabolites from Diaporthe sp.associated with Dendrobium nobile Lindl.Eighteen compounds including eleven new compounds named as diaporthsins A-K（1-11）were isolated.The structural types of the compounds are polyketide,and benzene ring derivative.Compound 11 showed antifungal activities against Diaporthe sp.and E.Coli,with MIC of 16μg/m L.Compound 9 exhibited moderate inhibition against A549.Compounds 5,14,17 and 18 displayed lipid lowering effects on triglycerides（TG）in steatotic L-02 cells.In chapter 5,the metabolites from the rhizospheric（Paraphaeosphaeria verruculos）TPT9X2 associated with Dendrobium officinale were studied.Twenty-three compounds including six new compounds named as paraverrucsin A-F（1-6）were discovered from P.verruculos.Paraverrucsin A-C（1-3）possessed a novel decarboxylated skeleton compared with trichocladinols.The relative configuration of the new compounds（1-6）were determined by using DP4⁺possibility analysis method.Coculture of P.verruculos and host Dendrobium officinale contributed to the enhancement of antifeedant and antiphytopathogenic activities.Compounds 1-14 showed moderate inhibitory activity against four plant pathogens（Colletotrichum gloeosporioides,Didymella glomerata,Nigrospora oryzae and Paraphaeosphaeria verruculosa）.Compounds 2,3 and 9exhibited potential antifeedant activitiy against silkworm larvae with EC₅₀ values of 13.9,13.9,and 18.2μg/cm².Most compounds displayed insect antifeedant activities,with antifeedant index percentages ranging from 42.0 to 93.0%,at a concentration of 50μg/cm².Compounds 1-6 and 14 showed selective weak cytotoxicity against SW480 with inhibition ratios of 32-38%at a concentration of 40μM.The sixth chapter was mainly about the active metabolites from the liquid co-culture of two rhizospheric Cladosporium sp.associated with Dendrobium officinale.Eleven known compounds were isolated.The structural types of the compounds are polyketide,steroid and benzene ring derivative.Compound 1,3,8 and 9 showed antifungal activity against four plant pathogens（Colletotrichum gloeosporioides,Dymella glomerata,Nigrospora oryzae and Paraphaeosphaeria verruculosa）,with MIC of 4-128μg/m L.The seventh chapter mainly focused on the the metabolites from rhizosphere Neocosmospora sp.associated with Dendrobium devoninum Paxt.Eight known compounds were isolated from Neocosmospora sp.The structural types of the compounds are fusarium,steroid and nucleoside.Lucilactaene（1）and NG-391（2）were obtained from Neocosmospora for the first time.Compounds 1 and 2 showed antifungal activity against four plant pathogens（Colletotrichum gloeosporioides,Didymella glomerata,Nigrospora oryzae,Paraphaeosphaeria verruculosa and Neocosmospora sp.）,with MIC values of 4-128μg/m L.