Studies On The Secondary Metabolites Of Soil-derived Actinomycetes

Actinomycetes are an important source of secondary metabolites with antibacterial,anti-tumor,anti-virus,anti-parasitic and other biological activities.Most of these compounds are widely used as drugs for clinical treatment or adjuvant treatment of various diseases.In this paper,40 strains of actinomycetes were isolated from the original ecological soil in Gaoan City,Jiangxi Province and Baicheng City,Jilin Province.Two soil actinomycetes with rich secondary metabolites,Streptomyces angustmyceticus GA2-5-1 and Streptomyces sp.XH1-3-3,were selected as the target strains for large-scale fermentation through chemical screening,medium screening and activity screening.And the fermentation products of these two actinomycetes were extracted,separated and structured.By means of kinds of chromatography methods,including HP-20 macroporous adsorption resin,XAD-16N macroporous adsorption resin,silica gel column chromatography,ODS open column chromatography,Sephadex LH-20 column chromatography,thin layer chromatography（TLC）,semi-preparative HPLC and other chromatographic separation methods,The chemical components of the fermentation products of soil actinomycetes were separated.And the compound structure was identified by comprehensive application of ¹H-NMR,¹³C-NMR,ES-IMS,HRMS and other spectral techniques and literature search methods.A total of 14 compounds were isolated from the secondary metabolites isolated from soil actinomycetes strain Streptomyces angustmyceticus GA2-5-1.According to the physical and chemical properties and spectral data,9 compounds were identified,namely and trichostatin RK（1）,trichostatic acid（2）,genistein（3）,daidzein（4）,cyclo（Ala‐Phe）（5）,1H-indole-3-carboxylic acid（6）,dibutyl phthalate（7）,zarzissine（8）and nocardamine（9）.3 compounds were isolated from the Streptomyces sp.XH1-3-3,which were identified as nocardamine（9）,oxachelin（10）,cyclo（L-Pro-L-Phe）（11）.A total of 17 compounds were isolated from two soil-derived actinomycetes,and 11compound structures were identified based on physicochemical properties and spectral data.Among them,compound 8 was isolated from actinomycetes for the first time;compounds 1-7 and 9 isolated from Streptomyces angustmyceticus for the first time.In addition,the antibacterial activity of compound 1-7 was determined by paper disc diffusion method,and the results showed that 1-7 had no significant antibacterial activity against Escherichia coli and Staphylococcus aureus.Whole-genome sequencing combined with bioinformatics analysis found that Streptomyces angustmyceticus GA2-5-1 has a relatively rich secondary metabolite biosynthetic gene cluster,which provides an important experimental basis for further mining the secondary metabolites of this strain and elucidating its biosynthetic pathway.