Studies On The Screening Of Strains And The Secondary Metabolites From The Fungus Alternaria Sp.from The Bohai Sea

Natural products are an important source for the discovery of lead compounds.The sources of natural products mainly include animals,plants,and microorganisms.Among them,microorganisms have become an important resource for the development of new lead compounds due to their wide distribution and short growth cycle.Because of the special marine habitats,marine microorganisms form different metabolic pathways from terrestrial microorganisms,which can produce many secondary metabolites with novel structure and good biological activity.Marine fungi have large genomes,which can be knock out silencing genes and produce many compounds with novel structures and good biological activities.Therefore,more and more natural products experts are studying the secondary metabolites of marine fungi.Strain screening is the premise of fungal secondary metabolites research and the effective guarantee of obtaining new active natural products.85 strains of fungi from Bohai Sea were collected from the laboratory strain bank;The chemical screening methods such as thin layer chromatography(TLC)and high performance liquid chromatography(HPLC)were used to analyze the abundance and UV absorption of the compounds in the fermentation extracts of the strains,and five target strains were screened out.Finally,combined with literature review,Alternaria sp.HBU-2017-24 was selected as the research object.After fermentation,extraction,comprehensive use of normal silica gel column chromatography,gel column chromatography Sephadex LH-20,reversed phase column ODS chromatography and semi high performance liquid chromatography and other means of separation and purification,combined with NMR,HRESIMS,UV,IR,OR and ECD modern spectroscopy technology,identified sixteen compounds(1-16),including three steroids(1-3),eight dibenzo-α-pyrones(4-11),five perylene quinone derivatives(12-16),among which dibenzo-α-pyrones and perylenequinone derivatives are representative polyketones produced by Alternaria sp.,which have a wide range of biological activities.The antibacterial activity of some polyketide compounds was evaluated.Compound 4 had certain inhibitory activity against Staphylococcus aureus with MIC value of 12.5 μg/m L.Compound 10 showed inhibitory activity against Pseudomonas aeruginosa and Escherichia coli with MIC value of 25 μg/m L.Compound 11 displayed some inhibitory activity against Bacillus subtilis with MIC values of25 μg/m L.In summary,a library of HPLC fingerprints of laboratory strains was developed by resuspending,purifying,incubating them and performing thin-layer chromatography,HPLC analysis of crude ethyl acetate infusions,which provided the escort for subsequent secondary metabolite research in the laboratory;Studied on the solid secondary metabolites of rice from Alternaria sp.HBU-2017-24 led to the isolation of 16 compounds,and two dibenzo-α-pyrones with hydroxyl groups at C-9 were isolated for the first time from Alternaria sp.which enriched the chemical structure diversity of secondary metabolites of Alternaria sp.At the same time,some compounds have some antibacterial activity,which has a certain research value.