Secondary Metabolites Of Four Marine-derived Fungi And Their Bioactivities

Marine-derived fungi may develope different biosynthetic pathways from those of the terrestrial fungi, which might lead to the production of structurally unique and biologically active compounds, to adapt the special enviroment. Marine-derived fungi have become a research focus for their chemical and biomedical potential. The content of this dissertation includes the isolation, structure elucidation of chemical constituents from the marine-derived fungus Alternaria alternate EN24, the chemical investigation of endophytic fungus Penicillium chrysogenum EN24S (derived from marine alga Laurencia sp.), which displayed inhibitory activity against the growth of pathogenic fungus Alternaria brassicae in the initial dual culture test. In addition, various secdonary metabolites were obtained from marine sediment-derived fungus Penicillium commune SD17 cultured in liquid PDB medium and solid rice medium. Finally, a strain Rhizomucor variabilis EN189 (isolated from the inner tissue of the mangrove plant Rhizophora stylosa) was investigated for structurally novel and biologically active compounds.The compounds were isolated by a combination of column chromatography (CC) including silica gel, Sephadex LH-20, RP-18, and semi-preparative HPLC. The structures of these compounds were elucidated by means of spectroscopic methods including IR, UV, MS, and NMR, as well as by comparision with reference materials or literatures. 41 compounds were isolated from R. variabilis EN189, including 11 new indolediterpenes (RV22*, RV24*, RV28*, RV30*, RV31*, RV33*, and RV35*~ RV39*) and 30 known compounds, while 35 compounds were isolated from the culture extract of P. chrysogenum EN24S out of whihc, 9 were found to be new structures, including 2 new steroids (PC13* and PC14*), 2 new polyketides (PC32* and PC33*), 2 new two glycerol derivatives (PC30* and PC31*), and 3 new terpene derivative (PC1*, PC2* and PC35*). 12 compounds were isolated from P. commune SD17 cultured in liquid PDB medium, including 6 new azaphilone derivatives (PCO1*~PCO6*) and 5 known compounds, while 17 compounds were isolated from P. commune SD17 cultured on solid rice medium, including 1 new glycerol derivative (PCO13*), 1 new sesquiterpene derivative (PCO14*), 1 new meroterpenoid derivative (PCO15*), 10 known compounds. Finally, from the extracts of A. alternate, we obtained 16 compounds, including 2 new perylene derivatives (AA11* and AA12*) and 14 known compounds.Some of the purified compounds were evaluated for the antimicrobial and cytotoxic activities. In the antimicrobial screening, PC13* displayed potent inhibitory activity against the pathogenic fungus Aspergillus niger with a clear inhibition zone of 18 mm diameter at the concentration of 20μg/disk; PC35* displayed potent activity against pathogen A. brassicae with an inhibition zone of 17 mm in diameter at the concentration of 20μg/disk; PCO3* displayed activity against Methicillin resistant Staphylococcus aureus (MRSA), Pseudomonas fluorescens, and Bacillus subtilis, with the MICs of 16, 64, and 32μg/mL, respectively, while PCO5* displayed activity against MRSA and P. fluorescens with the MICs of 32 and 16μg/mL, respectively. PCO6* also displayed activity against P. fluorescens and B. subtilis with the MICs of 32 and 16μg/mL, respectively. Additionnally, we discovered the anmicrobial activity of the known compounds PC3 and PC7 for the first time. PC3 showed significant antibacterial activity against Methicillin resistant S. aureus (MRSA), P. fluorescens, P. aeruginosa, and Staphylococcus epidermidis, each with MIC of 8μg/mL. PC4 showed obvious activity against P. fluorescens and S. epidermidis each with MIC of 16μg/mL.In vitro cytotoxic assay, PC13* displayed selective activity against the tumor cell lines HeLa, SW1990, and NCI-H460 with the IC50 of 15, 31, and 40μg/mL, respectively; PC32* possessed activity against HepG2 cell line with the IC50 of 32μg/mL. PCO5*, PCO6*, and PCO7* showed selective activity against the SW1990 cell line with the IC50 values of 51, 26, and 53μM, respectively; RV24*, RV25*, RV26*, RV27*, RV28* and RV41* showed obvious selective activity against the A-549 cell line with the IC50 values of 6.3, 9.6, 11.5, 4.6, 9.2 and 8.4μM, respectively; and RV24*, RV25*, RV26*, RV27*, RV28*, RV33* and RV41* showed obvious selective activity against the hl-60 cell line with the IC50 values of 6.3, 8.1, 7.9, 4.5, 11.9, 9.1 and 8.4μM, respectively.In summary, by application of bio-assay guided isolation and various fermentation media, we have thoroughly studied the chemical and biological diversity of four marine-derived fungi, which has enriched the chemical structures of marine natural products.