Studies On The Secondary Metabolites From Two Alkalifast Actinomycetes

Alkaliphilic microorganisms are one kind of extremophiles. To contact badsurroundings, Alkaliphiles surely have special physiological features and metabolicpathway and thus could produce bioactive substances that general microorganismscan’t produce. But there is little report about alkaliphiles’ secondary metabolites. Inorder to discover bioactive new compounds derived from alkalifast actinomycetes, astudy is carried out by integrated chemical screening and bioactive screening. Thestudies contained isolation of microorganisms from marine plants and soil, screeningtalented strains from alkalifast actinomycetes by intergrated chemical and bioactivemethods, influence of alkaline on their secondary metabolites, compounds isolationby bioassay-guided fractionation, and the structural elucidation and bioactiveevaluation of pure compounds.42strains were isolated from3deep soil samples and3plants samples whichrespectively were collected from the Qingdao and Hainan.2talented strains,YIM80379and MBRL-204, were picked out from marine and desert microbial strainsbased on the cytotoxic assay using the P388, Hela, HL-60cell line by the SRBmethod and MTT method, on the antimicrobial activity by the plate method and onthe chemical assay by HPLC and TLC screening. YIM80379was identified asNocardiopisis alkaliphila sp. nov., and MBRL-204was Streptomyces sindenensis.After investigating effects of different alkaline stresses on secondary metabolitesof these2strains, large-scale fermentations were carried out to obtain the activeextracts respectively. By means of chromatography over silica gel column, SephadexLH-20, preparative TLC and semi-preparative HPLC, six (1-6) and seventeen (7-23)compounds were isolated from YIM80379and MBRL-204, respectively. Basing ontheir physico-chemical properties and spectral data (IR, UV, MS, NMR, etc.),structures of twenty three pure compounds were respectively determined. Amongthem there are three new compounds, including two2-pyrone derivatives (1,2), two phenazine derivatives (7,8), five diketopiperazine derivatives (17-21), eightquinolone derivatives (9-16) and others (3-6,22,23).The cytotoxicity of the compounds against human cancer cells was determinedby the SRB and MTT assay method. Compounds7and8showed moderatecytotoxicity against A549cells. Compounds1,2,7─16and23showed antimicrobialactivity against Pseudomonas aeruginosa, Enterobacter aerogenes, Escherichia coli,Bacillus subtilis, Staphyloccocus aureus and Candida albicans in the Kirby-Bauerantibiotic testing.On the whole, twenty three compounds were obtained from the two alkalifastactinomycetes, including two new2-pyrone derivatives and one sulfuratedcompounds. This study also provides an actinomycete strain to produce phenazinederivates and shows that the microbial secondary metabolites are affected by externalpH.