Isolation,Identificaion And Antimicrobial Activity Of The Secondary Metabolites From One Marine Actinomycete Strain

Actinomyces,especially streptomyces,as an important source of antibiotics,have always been one of the hotspots of natural products research.In this paper,a strain of marine actinomycete isolated from the sea water of Beihai,Germany,was studied.The 16 S r DNA sequence analysis indicated that the marine actinomycete had99% homology with Streptomyces sp.strain nenu_DS₂1.The marine actinomycete marked as AC1 in this experiment.It was found that the metabolites of AC1 were chemical diversity,and its extracts of ethyl acetate and n-butanol of rice fermentation showed strong antimicrobial activity against Rhizoctonia solani and Alternaria alternate.The actinomycete AC1 was fermented by rice and GAUZE?s liquid Medium separately and its metabolites were purified by silica gel column,gel column,C18 reversed-phase column and HPLC column combined with thin-layer chromatography?TLC?.The isolated compounds were identified by mass spectrometry?MS?,1D and 2D NMR?1H-NMR,13C-NMR,HMBC,HSQC?and their antimicrobial activities were evaluated.The final results were as follows:?1?Eight compounds?I-VIII?were isolated from rice-fermentation metabolites of AC 1.Among them,compound I is 2,3-dihydroxybenzamide.Compound II is pyramidamycin B.Compound VIII is flufuran.Compound V,VI,VII,identified as Amide compounds,was firstly isolated from nature.III and IV are new chemicals.Compounds I,II,III,IV,VII are benzamides and compounds V,VI,VIII are furan-type compounds.Two compounds,IX and X,were separated from the metabolites of GAUZE?s liquid Medium.Among them,IX was benzamide?3'-amino-3'-oxoprop-1'-en-2'-yl?.Compound X was identified as a new chain amide structure.Among the 10 compounds,compound VIII was the main component produced by the actiomycete AC1.?2?Ten isolated compounds were tested for their antimicrobial activity against five plant pathogenic fungi,including Botrytis cinerea,Alternaria mali,Alternaria alternata,Rhizoctonia solani,Exserohilum turcicum,and three pathogenic bacteria Staphyloccocus aureus,Escherichia coli and Bacillus subtilis by disk diffusion method.Among them,compound VIII had antifungal activity against Botrytis cinerea,Rhizoctonia solani and Alternaria mali.Compounds V and VI showed antimicrobial activities against Bacillus subtilis.X exhibited antibacterial activity against E.coli and Bacillus subtilis.The minimum inhibitory concentration?MIC?and minimum bactericidal concentration?MBC?of the above active ingredients were determined by microdouble dilution method.The MIC and MBC of VIII compound to Botrytis cinerea,Rhizoctonia solani and Alternaria mali were 128 ?g/m L,128 ?g/m L,256?g/m L and 512 ?g/m L,512 ?g/m L,512 ?g/m L,respectively.Compound V had MIC of 128 ?g/m L and MBC of 512 ?g/m L to Bacillus subtilis.Compound VI had MIC of256 ug/m L and MBC of 512 ?g/m L to Bacillus subtilis.The MIC and MBC of compound X to E.coli and Bacillus subtilis were 256 ?g/m L,256 ?g/m L respectively and 512 ?g/m L,1024 ug/m L respectively.In conclusion,10 compounds were isolated from the fermentation of a strain of marine actinomycete.Six of them were new natural products and four compounds had certain antimicrobial activity,which proved that the actinomycete had great potential to develop as fungicide.