Research On Secondary Metabolites From Two Coral-derivied Microorganisms Of South China Sea

Marine microorganisms living in high pressure,high salt,low temperature and other special environment,result in a great variety and novel chemical structures of the second metabolites.The structural diversity of its secondary metabolites resulting in a wide range of biological activity,is an important source of high activity and high efficacy of leading compounds.However,the traditional single culture method causes the silence gene of microorganisms unble to express,resulting in many secondary metabolites failed to produce.Therefore,through the strategy of "One strain many compounds(referred OSMAC)”activating the silence pathway of microorganisms to obtain novel structure of secondary metabolites has been a focus in this area with broad prospects.In this research,endophytic bacteria and symbiotic fungi were isolated from the coral of South China Sea.The ecology and chemical means were used to screen the target strains and OSMAC strategy was used to culture the target strains with different fermentation media and co-culture.It was found that it can make strains to produce secondary metabolites unproduced in the traditional culture.The endophytic bacteria Pelomonas puraquae sp.nov(B-2)and symbiotic fungi NG-15-3 were studied for researching their secondary metabolites.15 compounds were isolated from the EtOAc extraction of B-2.Among them,13 compounds were determined by NMR(1D,2D),MS,and literature analysis:pelopuradazole(3-1),3H-imidazole-4-carboxylic acid(3-2),2-methyl-3H-imidazole-4-carboxylic acid(3-3),1H-pyrrole-2-carboxylic acid(3-4),pelopurin A(3-5),pelopurin B(3-6),cyclo-(Hyp-Phe)(3-7),cyclo-(Pro-Tyr)(3-8),cyclo-(Phe-Gly)(3-9),cyclo-(Phe-Ala)(3-10),cyclo(Ala-Tyr)(3-11),cyclo-(Leu-Gly)(3-12),cyclo-(Gly-Val)(3-13).3-1 is proved as a new imidazole derivative;3-5 and 3-6 are firstly obtained as natural products.All the compounds were firstly isolated from the endophytic bacteria Pelomonas puraquae sp.nov(B-2).In addition,12 compounds were isolated from the EtOAc extraction of symbiotic fungi NG-15-3.11 compounds of them were determined by NMR(1D,2D),MS,and literature analysis:asperentin-8-O-methyl ether(4-1),5'-hydroxy-asperentin-8-O-methyl ether(4-2),monomethyl cladosporin(4-3),asperentin/cladosporin(4-4),1-O-methyl emodin(4-5),carviolin(4-6),physcion(4-7),3H-imidazole-4-carboxylic acid(4-8),cyclo-(Phe-Gly)(4-9),cyclo(Gly-Pro)(4-10),preechinulin(4-11).4-3 is a new dihydro isocoumarin natural product.4-8 is a precursors of the monodehydro-2,5-diketopiperazines,which showed varied biological activity.