Study On The Secondary Metabolites From Symbions

This dissertation showed the structure elucidation and bioactivity evaluation of secondary metabolites produced by two symbiotic microbes including one marine fungus Alternaria sp.isolated from the deep sea sediment which collecteded South Atlantic Ocean and symbiontics actinomycete Streptomyces sp.obtained from the belly of Odontotermes formosanus.The crude extracts obtained from the fermentation broth of the two symbionts were separated by a combination of chromatographies over silica gel and ODS reverse-phrase column,gel filtration over Sephadex LH-20 and semipreparative HPLC to yield to 27 compounds.The structures of twenty-two compounds contained three new compounds were elucidated by spectroscopic analyses including HR-ESI-MS,IR,1H NMR,13C NMR,HMQC,1H-1H COSY,HMBC,NOESY,CD and single-crystal X-ray diffraction.Furthermore,some of these compounds were assayed in vitro for antimicrobial and cytotoxic activities.The marine-derived fungus Alternaria sp.isolated from the deep sea sediment of South Atlantic Ocean has been shown to produce seventeen sesquiterpenes(1-16 and 20),of which 1-2 possess new structures and three polyketides(17,18 and 19).The absolute stereochemistry of compound 2 was assigned unequivocally through a combination of NMR experiments and single-crystal X-ray diffraction analyses(CuKa).It was the first time to report the crystal structure of tricycloalternarene compound.The structure of 1 possessed a pyran ring and a furan ring,which was discovery for the first from the fungus Alternaria sp..In addition,compound 1 and 2 showed no antibacterial activity against Streptococcus pyogenes ATCC 19615,Mycobacterium smegmatis CGMCC 1.562,Cryptococcus neoformans ACCC 20337,Bacillus subtilis CICC 10285 and no cytotoxic activity against HCT116,MCF-7 and HeLa.Repeated column chromatographies of the extract from the culture of the termite-associated actinomycete Streptomyces sp.BY-4 led to the isolation of seven ansamycin compounds(21-27),of which one(23)was a new compound.The new compound possessed rarely dienomycin structure and so far only one compound has been reported by Japanese chemist.Finally,recent advances concerned the marine-derived fungus were reviewed briefly in this thesis.