Studies On The Chemical Constituents And Bioactivities Of Four Fungi

Fungal natural products play important roles both in natural medicines and leading compounds.This dissertation focuses on the chemical constituents of four fungal species to explore their structural diversity and their potential biological activities.It consists of five chapters,and the first four chapters introduce the chemical constituents and bioactivities of Trichothecium crotocinigenum(an endophytic fungus derived from potato),Paraphaeosphaeria sporulosa(an endophytic fungus derived from kiwi),Trametes velutina and Irpex lacteus,successively.The fifth chapter is a review on the topic of ‘Metabolites with remarkable antimicrobial activity from plant endophytic fungi(2012-2021)’.A total of 90 compounds(37 new compounds,including one indole alkaloid with a novel skeleton)were isolated from the solid fermentation extracts of these four fungi.Normal and reverse-phase silica column,Sephadex gel,MPLC and HPLC were used for separation.And the structures were established by extensive spectroscopic methods,quantum chemistry calculations,and X-ray diffraction experiments.Compounds include polyketides,terpenoids,alkaloids,glycosides,peptides,and so on.Some of them were evaluated for their bioactivities,and several active molecules were found.Chapter 1.Chemical and bioactive constituents from T.crotocinienum.T.crotocinienum is an endophytic fungus derived from the healthy tissues of potatoes.This fungus was proved to exhibit antifungal activity against phytopathogens of potatoes in a preliminary study.Chemical investigation of T.crotocinienum led to the isolation of 49compounds(23 new compounds,including one indole alkaloid with a novel carbon skeleton.)They belong to sesquiterpenoids,glycosides,amides,peptides and indole alkaloids,respectively.Several compounds displayed inhibitory activity against phytopathogens of potato and cytotoxicity towards MCF-7 cells.Chapter 2.Chemical and bioactive constituents from P.sporulosa.Pseudomonas syringae pv.actinidiae(Psa)is the pathogen of kiwifruit and causes canker diseases in kiwifruit.In order to find a safe and effective fungicide,P.sporulosa,an endophytic fungus derived from the healthy branches of kiwi was investigated.Chemical investigation of this fungus leading to the isolation of 18 compounds,including 4 new isobenzofuranones and 2 new isocoumarins.All of these compounds were evaluated for antibacterial activity against Psa(pathogen of canker disease),six compounds showed antibacterial activity with MIC ranging of 25-100 μg/m L.Chapter 3.Chemical investigation of T.velutina.T.velutina is a kind of white-rot fungus of the genus Thrombolia in the family Poraceae.A total of 17 compounds(including one new drimanes sesquiterpene,one glycoside and two fatty amines)were isolated from the rice fermentation extract of T.velutina.Chapter 4.Chemical and bioactive constituents from I.lacteus.I.lacteus is a pathogenic wood decay fungus.It was reported to produce active metabolites with novel structures in preliminary work.The chemical investigation of the strong polar portion of its rice fermentation extract led to the isolation of 6 compounds,including 2 pyridine derivates and 2 furan derivates.All of these compounds were evaluated for their cytotoxicity towards Hela cells and activity of inhibitory on NO production,however,none of them exhibited any activity.Chapter 5.Metabolites with remarkable antimicrobial activity from plant endophytic fungi(2012-2021)Plant endophytic fungi are a kind of fungi which inhabit the healthy tissue of the host plant without causing disease.Endophytes were reported to play important roles in plant defense systems of plants through producing metabolites with diverse activities.Therefore,endophytes were regarded as an important source of drugs and researched widely.This chapter reviewed metabolites with remarkable antimicrobial activity which are comparable or superior to the positive controls from plant endophytic fungi in last decade.These metabolites can be further studied as lead compounds of new antimicrobial agents.