Bioactive Secondary Metabolites From Three Marine-derived Microorganisms Based On Different Culture Methods

We selected three different ocean samples including mudflats,mangrove soils and deep-sea sediments,and 102 marine fungi,132 marine actinomycetes and 10 marine bacteria were isolated in total.Through the TLC,HPLC analysis and bioactivity evaluation,three marine microorganisms including the marine-derived Streptomyces sp.SS17F,Streptomyces sp.HNA101 and Alcanivorax sp.SHA4 from different marine environments were selected,and their secondary metabolites and bioactivities were studied systematically.Three target marine microorganisms were fermented by the two different culture methods,and the fermentation products were extracted by ethyl acetate.The separation and purification of ethyl acetate extracts were performed by Sephadex LH-20 column chromatography,silica gel column chromatography,MPLC and HPLC.The structures were elucidated by NMR and LC-MS data,and the absolute configurations of the new compounds were elucidated by X-ray diffraction analysis,ECD,Mosher's and Marfey's methods.Seventeen compounds,including five new compounds included,were isolated and identified from the fermentation of the SS17F.The five new compounds are lactoquinomycin C(13)and thioquinomycins A-D(14-17).Twenty-five compounds including eleven new compounds and one new natural product were isolated and identified from the fermentation of the strain HNA101.The eleven new compounds are 2-methoxy-xanthorrhorrhoeol(22),(E)-4-(2-(1H-indol-3-yl)vinyI)-quinazoline(27),alokicenone A-1(34-42)and the one new natural product,2-hydroxy-xanthorrhorrho-eol(20).Twelve compounds including one new compound and one new natural product were isolated and identified from the marine-derived Alcanivorax sp.SHA4.The new compound is acantimycic acid(54)and the new natural product is 7-hydroxy-2H-1,4-benzothiazin-3(4H)-one(44).The results of bioactivity tests indicated that compounds 14-17 showed moderate cytotoxicity and inhibitory activities against protein kinase,and compounds 34 and 35 exhibited significant cytotoxicity against HCT116 and SW620 cancer cell lines with IC50 values from 0.63 to 3.49 ?M,and compound 54 exhibited well neuroprotective effect.By comparing the effects of different culture methods on the secondary metabolites of the target strains,it was found that the Gause's liquid medium has the advantages of short time cycle,stable production with high bioactivity,while the rice solid medium has the higher production and the second metabolites more abandent.This culture method is easier to obtain new compounds.