Study On Secondary Metabolites From Soil-derived Actinomycete MZ1 And Fungus JX1 As Well As Their Antimicrobial Activities

Soil is the principal ecosystem for microorganisms on earth,and many attentions are focused on soil-derived actinomycetes and fungi owing to their special faculties of producing secondary metabolites with a broad diversity of skeletons and bioactivities.Therefore,many efforts are made to discover the bioactive constituents from antagonistic microorganisms in soil,the natural treasure-house.The active and novel secondary metabolites could provide precursors for prevention and control pests in agriculture as well as for developing new drugs in clinics,which will bring significant economic and social benefits.In this thesis,the plate streaking culture method was taken to isolate and purify strains from soil samples collected from the white-headed langur conservation of Chongzuo and the gibbon conservation of Bangliang in Guangxi province.The target strains were selected for further research based on bioactivity screening results and chromatographic profiles.12 active constituents were found through scale-up fermentation,extract,isolation,identification,and bioassay evaluation.(1)12 strains(named as MZ1-MZ12)were isolated and purified from soil sample collected from the white-headed langur conservation of Chongzuo.Among them,strain MZ1 were selected on the basis of its HPLC(High Performance Liquid Chromatography)and HPLC-MS(High Performance Liquid Chromatography-Mass Spectrometry)characters as well as preferable antifungal activity.It was identified as Streptomyces ahygroscopicus based on 16 S r RNA gene analysis.After scale-up fermentation,7 compounds were isolated from the extract using chromatographic methods,4 of which were elucidated as tetramycin B(1),TX1-3(2-4).They all belong to tetrene macrolides and TX1-3 are new compounds.The preliminary bioassay experiments showed that all of them displayed apparent inhibition against a plant pathogenic fungus strain of Fusarium oxysporum f.sp.cucumerinum.(2)9 strains(named as JX1-JX9)were isolated and purified from soil sample collected from the gibbon conservation of Bangliang.Strain JX1 exhibited better HPLC and TLC(Thin Layer Chromatography)profiles as well as moderate antibacterial activity,and thereby were selected for further study,which was identified as Penicillium verrucisporum based on ITS gene analysis.12 compounds were obtained by using column chromatograph and prep-HPLC(preparative HPLC),9 of which were deduced as(-)-sclerodin(1),physcion(2),communol F(3),4,6-dihydroxy-9,10-dimethylacetophenone(4),verphenalenone(5),(2S,3S)-1,4-di(4-methoxyphenyl)-2,3-butanediol(6),(-)-scleroderolide(7),(+)-scleroquinone(8),(-)-trypethelone(9)based on cumulative analysis of 1D,2D NMR(Nuclear Magnetic Resonance Spectroscopy)and MS(Mass Spectrometry)as well as comparison the spectra data with literatures.Most of them showed potential antimicrobial activity.New compound 5 just showed moderate effect on Bacillus subtilis(MIC: 64 μg/m L)while communol F(3)displayed apparent inhibition against both B.subtilis and Saccharomyces cerevisiae with the same MIC(Minimum Inhibitory Concentration)value of 16 μg/m L,as well as moderate inhibition against Escherichia coli(MIC: 64μg/m L).In this paper,preliminary study of main secondary metabolites of a soil actinomycete MZ1 and a soil fungus JX1 led to 13 compounds isolated and identified,including 4 new ones.Meanwhile most of them have obvious antimicrobial activity in vitro,which would help to discover antimicrobial lead compounds.