Studies On The Secondary Metabolites Encoded By Two Streptomyces Strains

Objective:In present situation,the condition of drug resistance is very serious.On the one hand,the main means of treatment of cancer are surgery,radiotheraphy and chemotherapy,but most of medicines have obvious side effects.With the emergences of a large number of tumor multidrug-resistant cell lines,the efficacy of chemotherapy drugs reduced.On the other hand,antibiotic abuse phenomenon is increasingly serious,due to our misuse of medication habits and concept,which leads to producing of resistant bacteria and super-resistant bacteria,decreasing the efficacy of antibiotics.Finally,various treatment means gradually lead to failure.If the phenomenon could not be improved,the global death caused by resistance will rise sharply,of which Asia accounted for about half of the proportion.Therefore,it is imminent to find new lead compounds with antitumor or antibiotic activities.With the deep understanding of the side effects of chemical drugs and the global initiative to return to the nature methods,natural medicines attract more and more attentions.So,development of natural drugs become popular in the world.Natural medicine has a wide range of sources.As an important source,microorganism includes three categories,such as bacteria,actinomycetes,and fungi(of which actinomycetes accounted for about 45 %).Selman Waksman systematically detected soil microbes and found that Streptomyces were the most important microbial sources in actinomycetes(accounting for up to 90 %).The secondary metabolites were structurally rich and active,and could be used for antitumor,antimalarial,antibacterial,antiviral,immunosuppressive,etc.Since the golden age of antibiotic digging has been kicked off,a large number of significant natural products have been obtained from Streptomyces.Currently,2/3 of the clinical antibiotics derived from Streptomyces,including the streptomycin which is preferred drug of tuberculosis,the tetracycline which is the treatment of cholera and plague,the chloramphenicol which is preferred drug for typhoid and paratyphoid,the vancomycin which is treatment of bacterial infection,and so on.It can be seen that Streptomyces are the main source of natural medicine,which has an important commercially valuable species of actinomycetes.In present days,the research scope of Streptomyces is mainly concentrated on two major sources i.e.soil and ocean.Therefore,two strains of Streptomyces were selected,one from soli and the other from ocean,to explore new antitumor or antibiotic of lead compounds in this project.Methods:A strain of Streptomyces nojiriensis SYSUS00008 was screened from eight strains of terrestrial actinomycetes,derived from Mohe and Huangshan by combined screening strategies,including antibacterial activity test,cultural condition optimization,and HPLC-DAD analysis.A strain of Streptomyces lusitanus SCSIO LR32 from the deep sea of the South China Sea was selected as the target strain.These two strains were cultivated using ISP2 and modified RA(with sea salt)media,respectively.Compounds were obtained through purification using silica gel column chromatography,medium performance liquid chromatography,Sephadex LH-20 chromatography,and semi-preparative high performance liquid chromatography.The chemical structures were identified on the basis of HR-ESI-MSand NMR spectral analyses,as well as literature comparison.The bioactive compounds were screened out by antibacterial and cytotoxic assays.Result:1.Ten phenazine compounds were isolated from Streptomyces nojiriensis SYSUS00008,and 5 compounds were characterized as izuminoside A(1),izuminoside D(2),solphenazines E(3),N-(2-Hydroxyphenyl)-acetamide(6),diastaphenazine(8).Izuminoside D(2)was a new structure.The previously reported literatures showed that phenazine compounds had a wide range of activities in the anti-cancer,antibiotics,and biofilm eradication field.Natural phenazine compounds have broad activities,not only showing significant inhihbitory effect for wheat all disease,rice wilt and other pathogens,but also for tuberculosis,leukemia,mycobacterium tuberculosis and atypical acid bacteria and leprosy and other diseases treatment,it plays an important role in the medicine and agriculture field.2.Six angucycline compounds were isolated and characterized from Streptomyces lusitanus SCSIO LR32,including grincamycin I(11),grincamycin J(12),grincamycin K(13),A-7884(14),grincamycin B(15),and grincamycin(16).Grincamycin I(11),grincamycin J(12),grincamycin K(13)were new compounds.Cytotoxic activities of compounds grincamycin I-K(11-13)and A-7884(14)were evaluated against five human tumor cell lines,such as human breast cancer cell line MDA-MB-435 and MDA-MB-231,human large cell lung cancer cell line NCI-H460,human colon cancer cell line HCT-116,human hepatocellular carcinoma cell line Hep-G2,and one human normal mammary epithelial cell line MCF-10 A using the MTT method.The results showed that Grincamycin J(12)and A-7884(14)exhibited cytotoxic activities against the six human cell lines with IC50 values ranging from 0.4 to 6.9 ?M.Grincamycin I(11)exhibited moderate cytotoxic activity with IC50 values ranging from 2.9 to 25.9 ?M while grincamycin K(13)showed weak exhibition.In addition,A-7884(14)showed antibacterial activity against Micrococcus luteus with a MIC value of 1.95 ?g/mL.Conclusion:Numerous phenazine compounds and angucycline compounds were produced by Streptomyces nojiriensis SYSUS00008 and Streptomyces lusitanus SCSIO LR32,respectively.Streptomyce strain is an important source of active lead compounds.