Isolation,Purification And Identification Of Bioactive Secondary Metabolites Produced By Marine Actinomycete TXC6-16

The strain TXC6-16 was provided by First Institute of Oceanography,State Oceanic Administration?Shandong,China?.The fermentation supernatant of this strain has strong antimicrobial activity against Alternaria solani and Ralstonia solanacearum.The antimicrobial compounds produced by TXC6-16 were obtained by bioactivity-guided isolation using kinds of separation and purification technology,such as organic solvent extraction,Sephadex LH-20 and HPLC column chromatography.We discovered two active secondary metabolites named TXC6-16-S4 and TXC6-16-TLC-5 in the end.The spectra data of IR,¹H-NMR,¹³C-NMR,2D NMR and HR-ESI-MS were used to identify these two compounds.These two compounds were identified as new ?-butyrolactons in SCI Finder database.The molecular formula of TXC6-16-S4 and TXC6-16-TLC-5 were confirmed as C₁₃H₁₆O₉ andC₁₉H₂₈O₉,respectively.These two compounds are analogs with a molecular weight of 316 and 400,respectively.The standard curve was established using HPLC to analyze the two compounds in the process of fermentation and separation.The minimum inhibitory concentration?MIC?of TXC6-16-TLC-5 against the tested pathogenic microorganisms were all more than 375 ppm,meanwhile the MIC of TXC6-16-S4 against certain pathogenic bacteria,such as Pseudomonas syringae and Erwinia sp,was only 50 ppm.It was obviously determined that TXC6-16-S4 showed better activity against pathogenic bacteria than TXC6-16-TLC-5.But the MIC of TXC6-16-S4 against Alternaria alternata and Colletotrichum sp.,both of which were pathogenic fungal,were as high as 375 ppm.Thus,pathogenic bacteria were more susceptible to TXC6-16-S4 than pathogenic fungi.The marine actinomycete strain TXC6-16 was identified by 16S rDNA gene sequence analysis and the study of morphological,physiological and biochemical characteristics.The results showed that the strain TXC6-16 was Streptomyces ghanaensis which belonged to Streptomyces family.