Studies On The Secondary Metabolites Of Two Salt-tolerant Fungi From Yellow River Delta

The living and nurturing environment for salt-tolerant microorganisms is special,but general microorganisms hard to exist. It may have special biological metabolicpathways in such an environment, which can produce vagarious metabolites. YellowRiver Delta Nature Reserve in Dongying Shandong has serious soil salinization, soilwith high salinity in many places, and interaction of land and sea at the same time,forming a relatively unique ecological environment. The area exist salt-tolerantmicroorganisms which can produce novel structure and activity compounds, worthyof further study.In order to study the source of the Yellow River Delta salt-tolerant strains ofsecondary metabolites, we combine chemistry and bioactive screening integrationmodel, a study is carried out to the Yellow River Delta saline soil microorganisms.The main contents are: separation and purification of salt-tolerant microorganisms;screening tolerant fungi and optimization of fermentation conditions; isolation andpurification of secondary metabolites from salt-tolerant fungi; identification thestructure and preliminary evaluation activity of the monomer compound.We obtained192salt-tolerant strains, including121fungal strains,56actinomycete strains and15bacterial strains which were isolated from soil samples ofYellow River Delta, sponges and coral sample of Xisha Islands as well as deep waterand mud samples of South China Sea. Through integration screening methodcombination of chemistry and activity, two salt-tolerant fungi OUCMDZ-2713andOUCMDZ-2702were screened to study their secondary metabolites. The two fungiwere identified as Cladosporium cladosporioides and Acremonium sp., respectively.By examining the effects of different cultivation methods, culture media, pH andsalinity on secondary metabolites of the two sale-tolerant fungi, the large-scalefermentation conditions were determined. Using vacuum and pressure silica gelcolumn chromatography, thin layer chromatography, gel column chromatography andsemi-preparative HPLC chromatography,22compounds were isolated fromfermentation products of two fungal strains. Combined with mass spectroscopy andNMR spectroscopy and other methods, compounds1-17were identified (Figure1) which included two lactams (1,2), seven diketopiperazines (3-9),3fatty acid esters(13-15), two nucleosides (10,11), a diol (12), a pyrrolidine formamideand (16) and asterol compound (17). Compounds1,2and13are new compounds.The antibacterial activities of some compounds were preliminary evaluated bypaper disk diffusion method. The cytotoxic activity of some compounds on MCF-7,A549and K562cells were preliminary evaluated by MTT and CCK-8methods. Theresults showed no antibacterial and cytotoxic activities were observed, indicating thatthe active compounds were not obtained.In summary, two salt-tolerant fungi were obtained by integrated chemistry andactivity screening method. And their secondary metabolites were study. As a result,17compounds including three new ones were isolated and identified, suggesting thatsalt-tolerant fungi are potential to research, worthy of further exploration.