| 其他摘要 | Marine microorganisms possess highly diverse metabolism pathways. Among them, the research on the secondary metabolites of marine endophytic and epiphytic fungi has drawn the interest of more and more natural product chemists. In this dissertation, three marine algicolous fungal strains including Aspergillus oryzae cf2 (derived from the marine red alga Heterosiphonia japonica), Aspergillus flavus cf5 (derived from the marine red alga Corallina officinalis), and Eurotium rubrum cf14 (isolated from the green algae Codium fragile) were selected as aimed strains to be fermented for further investigation of chemical constituents. Most of the isolated compounds were preliminary screened on their bioactivities. The compounds were isolated from the fermentation extracts by repeated column chromatography (CC) on silica gel, RP-18, and Sephadex LH-20, as well as by preparative thin layer chromatography (PTLC), preparative HPLC and recrystallization. The structures of these compounds were elucidated by means of spectroscopic methods including IR, UV, EI-MS, HR-EI-MS, 1D-NMR (1H-NMR, 13C-NMR, DEPT) and 2D-NMR (1H-1HCOSY, HSQC, HMBC, NOESY). Totally, 33 compounds were structurally elucidated. From the extracts of A. oryzae cf2, 11 compounds were isolated and structurally elucidated. Among them, four were found to be new compounds, including three new indoloditerpenes (AO1-AO3) and a new steroid (AO7). From the extracts of fungus A. flavus cf5, 11 compounds were isolated and structurally elucidated. Among them, two were found to be new compounds as one new steroid (AF1) and one new oxylipin (AF7). From the extracts of fungus E. rubrum cf14, 11 compounds were also isolated and structurally elucidated. Among them, one steroid (ER1) was found to be new compound. Most of the pure compounds were screened for their insecticidal against brine shrimp, acetylcholinesterase (AChE) inhibitory and antimicrobial activities. It was revealed that the compounds AO1, AO4, AO5, AO11 (ER8) and AF10 exhibited more active in the assay for insecticidal activity against brine shrimp (Artemia salina) than the others. The results of acetylcholinesterase (AChE) inhibitory activity showed that all compounds possessed low activity to modulate AChE. In the antimicrobial scavenging assay, compound AO2, AO3, AF10, ER2 and ER3 showed weak inhibitory activity against Staphylococcus aureus, compound AO3, AF5 and ER2 exhibited moderate or weak inhibitory activity against Escherichia coli. However, all compounds exhibited no activity against plant pathogenic fungi Colletotrichum lagenarium and Fusarium oxysporium. In this dissertation, secondary metabolites of three strains of marine algicolous fungi were thoroughly studied. It enriched the chemical structures of marine natural products. Through bioassay, some compounds were found to be active. It may be helpful to exploration of marine microorganisms. |
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