Chemical Diversity And Bioactivities Of Secondary Metabolites From Three Mangrove-derived Fungi

Intertidal zone is the area that is above water at low tide and under water at hightide, and have cyclical variations in earth’s orbit. Due to the unique living conditionsof intertidal zone, microorganisms derived from mangrove environments possessspecial hereditary and physiological character, and have the capability to producespecial secondary metabolites with unique skeletons and excellent bioactivities.By chemical analysis and biological activity screening,1productive fungi and2potential medicinal value strains were chosen to further research for their activecomponent. Studies include screening of bioactive fungal strains, purification andstructural elucidation of the secondary metabolites, preliminary evaluation forbioactivities of pure compounds and exploring the biosynthetic pathways of the novelcompounds.Three target strains were screening from our fungi resource bank established bymangrove-derived fungi, including Aspergillus sp. H-2-11, Aspergillus nigerZHN2-20and Aspergillus. glaucus HB1-19. A large scale fermentation of three fungiwas performed respectively and the crude organic solvent extract was subjected tosilica gel column, Sephadex LH20, PHPLC and etc.In all, the present work on the chemical investigation of above threemangrove-derived bioactive fungal strains leads to73compounds. From fungusAspergillus sp. H-2-11,26compounds (1-26) were isolated; from fungus Aspergillusniger ZHN2-20,20compounds (27-46) were isolated; from fungus Aspergillus.glaucus HB1-19,27compounds (47-73) were isolated.Basing on their physicochemical properties and spectral data (UV, IR, MS, NMR,CD, and X-ray), combined with chemical reactions, structures of the73purecompounds were respectively determined. Among them there are15meroterpenoids (1-15，37-40),3alkaloids (27，44，71),36polyketides (16-17，28-30，33-36，45-50，52-70，72-73),5steroids (31-32，41-43),1glycosides (51) and9polyene-polyol(18-26). Twenty compounds are new, including1unusual skeleton austin-likemeroterpenoid (1),1rare oxidation austin-like meroterpenoid (2),2unusual skeletonpolyenen-polyol (18,19),6noval polyenen-polyol (20-25),1new austin-likemeroterpenoid (3),1new pyrrolidine alkaloid (27),2new depsidones (28,29),1newsteroid (31),4new benzene derivatives (47-50),1new glycosides (51), and1newnatural product of depsidone (30).In the study, we established the relative and absolute configurations of unusualskeleton austin-like meroterpenoid (1) by the combination of2D NMR and X-Ray.We determined the plan structure of8polyenen-polyol (18-25),1pyrrolidine alkaloid(27), and other7compounds (28,29,47-51). We also determined the relativeconfigurations of new steroid (31) by NOESY, coupling constants and opticalrotations.Summarily,73compounds were isolated and identified from3aimed fungalstrains, including20new compounds and1new natural product. Furthermore, weestablished part of their absolute configurations of the isolated compounds andpossible biosynthetic pathways of the austin-like meroterpenoids (1-15). We alsoevaluated the bioactivities of pure compounds, and15of which showed significantactivity. Based on the results of this research, we could do further more.