Optimization Of Culture Conditions And Secondary Metabolites Of Two Sargassum Sp. Derived Endophytic Fungus

In this dissertation, the static fermentation extracts of4endophytic fungal strains(isolated from tropical marine organisms) on4kinds of liquid cultural mediums, werecomprehensively evaluated on the basis of weight of fermentation extracts along with TLC,NMR and HPLC analysis. Two fungal strains, Aspergillus wentii EN-48andCladosporium sp. EN-49, all isolated from the brown alga Sargassum species, wereselected as aimed strains, and were fermented on50liters of PDB and30liters of H1cultural medium respectively, for further investigation of their chemical constituents.Some of the isolated compounds were evaluated for their bioactivities.The compounds were isolated from the fermentation extracts by repeated columnchromatography (CC) on silica gel, RP-18, and Sephadex LH-20, as well as by preparativethin layer chromatography (PTLC), semi-preparative HPLC and recrystallization. Thestructures of the isolated compounds were elucidated by means of spectroscopic methodsincluding IR, UV, EI-MS, FAB-MS, HR-ESI-MS,1D-NMR (1H-NMR,13C-NMR, DEPT)and2D-NMR (1H-1H COSY, HMBC, HMQC) as well as by chemical methods. Totally,33compounds were isolated and structurally elucidated from the extract of Aspergillus wentiiEN-48. Among them,9compounds were found to be new structures, including fiveanthroquiones and derivities (AW1*^AW3*, AW9*and AW11*), four norditerpenes(AW16*^AW18*and AW12*). From the extracts of the fungus Cladosporium sp. EN-49,18compounds were isolated and structurally elucidated. Among them, three were found tobe new compounds as ring-opening derivatives of12-membered macrolides (C1*^C3*).Furthermore, the reported structure of AW15was revised by the X-ray crystallographicexperiment. The possible biosynthesis of some of the isolated compounds were alsodiscussed.Some of the isolated compounds were evaluated for antibacterial and fungicidalactivity and vitro cytotoxicity activity. It was revealed that the new compound AW17*exhibited strong inhibitory activity against Candida albicans with MIC of16.0μg/mL. AW14～AW16*showed potent cytotoxicities against6different cancer cell lines withIC₅₀values of varies from5to28μg/mL. At the concentration of100μg/disk, the knowncompound AW5showed weak inhibitory activity against the phytopathogenic fungus(Alternaria brassicae (berk.) Sace) with inhibition zone of φ=6.0mm, while compoundsC-1*^C-5displayed moderate inhibitory activities against Aspergillus niger withinhibition zone of φ=10.0mm, and moderate inhibitory activities against Staphylococcusaureus with inhibition zone of φ=8.0mm, as well as weak inhibitory activity againstEscherichia coli with inhibition zone of φ=6.0～6.5mm.