Chemical Investigation Of Metabolites From Four Strains Of Plant Endophytes And Their Biological Activities

This dissertation consists of three chapters.Chapter 1 expounds the investigation on metabolites of three endophytic fungi from the plant.And the biological activities of some compounds were tested.Chapter 2 illustrates the isolation and identification of one endophytic actinomycete.Chapter 3 summarizes the progress of metabolites from endophytes origin in recent 10 years.By multiple chromatographic techniques and modern spectroscopic methods,a total of 34 compounds with different structure types,including polyketides,alkaloids,phenols,phenylpropanoids,glycosides,steroids,fatty acids and so on,were isolated and identified from three endophytic fungi.Among them,two compounds were new.This investigation has enriched the chemical diversity of endophytic fungi derived from plants.Chapter 1 Chemical investigation on metabolites from three strains of plant endophytic fungi and their biological activitiesEndophytic fungi produce metabolites in different types of chemical structures due to their special habitats in plants.In recent years,quite a few studies have found that these compounds have extensive biological activities,such as anti-tumor,anti-virus,antibacterial,anti-inflammatory and so on,which turn endophytic fungi into a natural treasure for developing active compounds.The investigation carried out on the metabolites of three plant endophytic fungi,including Pestalotiopsis sp.SA-MB-4,Bjerkandera sp.M-12,and Arthrinium sp.HU-14.2,which led to the isolation and identification of 34 compounds,together with two new compounds.By multiple modern spectroscopic methods,the structures and spatial configurations of these compounds were identified.The main metabolites of Pestalotiopsis sp.SA-MB-4 were naphthopyrones,ergosterols,and alkaloids,while the major metabolites of Bjerkandera sp.M-12 included ergosterols,phenol,glycosides,and fatty acid.For Arthrinium sp.HU-14.2,its metabolites mainly consisted of pyridine alkaloids,acid anhydrides,olefin ketones,and phenol.The bioactivity detections on parts of these compounds were carried out.Fonsecinone A?pe-1?showed weak growth inhibitory activity to Colletotrichum litchi with EC₅₀ of 414.14±0.86?g/mL,while flavasperone?pe-5?showed weak inhibitory activity to C.litchi,and Rhizoctonia solani with EC₅₀ of 326.76±1.89?g/m L and 56.72±11.46?g/mL,respectively.Additionally,apiosporamide?ar-1?and 4-O-formyl apiosporamide?ar-2?exhibited potent growth inhibitory activity against C.litchi,R.solani,and C.gloeosporioides.The EC₅₀ of compound ar-1 was 29.92±0.35,18.47±1.54,and13.40±2.69?g/m L,respectively,while the EC₅₀ of compound ar-2 was 46.54±2.40,7.80±2.72,and 7.45±1.98?g/mL,respectively.Moreover,ar-1 and ar-2 had moderate cytotoxic activity on NCI-H1975,Hep G2,MCF-7,with IC₅₀ ranging from46.10 to 79.74?M.Furthermore,ar-1 and ar-2 displayed weak hypolipidemic activity.The inhibition rates of ar-1 and ar-2 to HMGR were 16.03±1.06%and17.33±0.79%,respectively,with the concentration of 50?M.This study enriches chemical diversity of metabolites in endophytic fungi,and provides a basis for the further discovery of active compounds from endophytic fungi.Chapter 2 Isolation and identification of one endophytic actinomycete from the plantEndophytic actinomycetes are an important resource of many active compounds,however,their growth are too slow that the isolation conditions are different from other endophytes.This study preliminarily explored the method of isolation of endophytic actinomycetes from plant leaves,and finally isolated a strain of endophytic actinomycete,identified and named Streptomyces sp.L5 by combination with morphology and molecular biology.The endophytic actinomycete was fermented and cultured with four different mediums.The fermentation products were qualitatively analyzed by HPLC.It was found that different nutrients had a certain influence on the accumulation of metabolites from Streptomyces sp.L5.After the amplified fermentation,two compounds of isoflavones were isolated and identified.It was preliminarily speculated that they might belong to the nutrient components of the culture-medium,and its true metabolites should be further studied.Chapter 3 Research progress on metabolites of endophyte and their biological activityEndophytes are an important source of natural products,its metabolite are very diverse in structure,including alkaloids,terpenoids,lactones,phenols and so on.These metabolites showed extensive biological activity,such as anti-tumor,antibacterial,antimalarial and so forth.In this chapter,the structures and biological activity of metabolites from endophytic fungi and endophytic actinomycetes in the last 10 years were briefly reviewed,and we described simplely the species of endophytes and the research methods of metabolites.Futhermore,we discussed the difficulties in the study of endophyte at the present stage,as well as the direction of future study.