Secondary Metabolites Of Three Endophytic Fungi

Symbionts supposed to have special biogenetic pathway due to the unique habitats and long-time co-evolution with their host have become a promising resource of numerous structurally diverse secondary metabolites with remarkable bio-activities.The dissertation presents the structure elucidation and bioactivity evaluation of secondary metabolites produced by three fungal strains isolated from Coccinella septempunctata L.,Raphanus salivas L. and Cynodon dactylon. The crude extracts derived from the cultures of the three symbionts were repeatedly fractionated by a combination of chromatographies over normal-and reverse-phase ODS silica gel, gel filtration over Sephadex LH-20 and HPLC to afford a total of 42 compounds. The 42 compounds of which 11 are new were elucidated by spectroscopic analyses including MS, UV, IR,CD, 1D and 2D NMR, and single-crystal X-ray diffraction. Furthermore, some of the natural products were found to have antifungal activities. Specifically:Aspergillus oryzae QXPC-4, an endophytic fungus,was isolated from of C septempunctuta L. The liquid fermentation, followed extraction and fractionation, gave 14 compounds including 3 new drimane sesquiterpenoidsand 4 new drimane sesquiterpenoidhydroxybenzene esters.All the compounds were evaluated for cytotoxic activity, however, no compounds showed significant cytotoxicity against the tested cell lines at a concentration of 20μM.The endophytic fungus MyrotheciumroridumQB-1 dwelling in the healthy leaf of R. sativus L.was shown to be capable of producing 11 compounds including 4 newsimple trichothecenes.Compounds 21 and 22showed significant antifungal activity against the tested fungal(MIC rangedfrom 10 to 5μg/mL). Compounds 18,21, 22, and 24showed significant cytotoxic activity againstHCT116, BGC823, and SW480 celllines (IC50<10μM).Aspergillus fumigatusCY018wasan endophytic fungi isolated from Cynodon dactylon. Repeated fractionation of the extract from Aspergillussp.CY018 could afford17known compounds, most of which are alkaloids.Furthermore, natural bioactive products from plant endophytic fungus were reviewed briefly.