Activation Of Secondary Metabolites Biosynthesis Stimulated By Chemical Epigenetic Inducer From Deep Marine Fungi Aspergillus Sp.SCSIOW2

Marine fungi have the potential to produce new bioactive substances due to their special living environment and metabolic mechanism. In recent years, scientists have consistently discovered new secondary metabolites with novel structures and unique bioactivities, which provide new precursors for natural products studies and drug development. Studies have shown that in the laboratory culture conditions, over 70%of the silent biosynthetic gene clusters are not expressed. Activation of these biosynthetic gene clusters will strongly enhance the diversities of the secondary metabolites of fungi, and provide important lead compounds for new drug development. Due to the close relationship between the biosynthesis of secondary metabolites of fungi and the epigenetic state of their gene cluster, scientists are capable of changing the secondary metabolites of microorganisms in a large scale and activating their gene expressions by epigenetic operations.Based on the mechanism of chemical epigenetic modification, the secondary metabolites of 30 strains of mangrove fungi and 6 strains of deep-sea derived fungi were screened after adding 5-azacytidine(5-AC) and Suberohydroxamic acid(SBHA)simultaneously. SCSIOW2(W-2) had shown obvious and stable changes after adding these stimulus, therefore it was selected for further studies in this thesis. First, W-2was identified as Aspergillus sp. based on the ITS rDNA sequencing analysis. Then,after fermentation using 5-AC and SBHA stimulus, 13 compounds were isolated and purified by normal phase silica gel column chromatography, Sephadex LH-20 gel column chromatography and HPLC. By now, structures of 10 compounds had been identified by spectroscopic analysis including 3 new eremophilane type Sesquiterpenes(compounds 2, 3, 4), 1 new cyclic dipeptide(compound 6).Compound 1, 2, 3, 4, 9,13 were tested for their anti-inflammatory activities. With concentration of 100 ?M, these compounds showed moderate inhibitions against nitric oxide production from Macrophage 264.7 cells stimulated by LPS and IFN-?. 9and 13 were tested by Alzheimer's disease model of drosophila. 9 could improve the learning disabilities of drosophila to the same level of memantine, which is a commercially available drug against Alzheimer's disease, while compound 13 did not have any effects.