Secondary Metabolites From Three Marine Sediment-Derived Fungi And Their Bioactivities

Complicated marine sedimentary environments are the habitats of a large number of organisms.In order to survive in these complex and extreme environments,some fungi tend to evolve and form unique metabolic systems to adapt to the living environments.This has led to the diversity of secondary metabolites.In recent years,the sediment-derived fungi have attracted great attention for natural product researchers.Research on the secondary metabolites of marine sediment-derived fungi allows us to have a better understanding of the fungal metabolic mechanism,hence contributing to the development and utilization of marine microorganism resources.This dissertation elaborated on the process and results of the research on the secondary metabolites and their bioactivities of three fungal strains,selected from 93 fungal strains obtained from the sediment of 23 stations in the Bohai Sea based on chemical and biological assays.As a result,33 compounds,involving teroidals,alkaloids,terpenoids,anthraquinones,benzopyranones,etc.,were isolated and identified.Additionally,the anti-microalgal and anti-bacterial activities of those compounds were evaluated.To begin with,after preliminary optimization of fermentation conditions,the metabolites were isolated by means of repeated column chromatography(CC)on silica gel,Sephadex LH-20 and RP-18 and preparative thin layer chromatography(pTLC)as well as semipreparative HPLC.Then the structures of these compounds were identified by spectroscopic methods including 1D/2D NMR and by comparion with those in literature.21 compounds were isolated and elucidated from Penicillium oxalate T4-6,including 3 benzene derivatives(P1-1~P1-3),1 lactone(P1-4),1 benzopyranone(P1-5),2 tetralin ketones(P1-6~P1-7),2 anthraquinones(P1-8~P1-9),1 rye ketone(P1-10),4 alkaloids(P1-11~P1-14),5 steroidals(P1-15~P1-19),1 terpenoid(P1-20)and 1 macrolide(P1-21).5 steroids were isolated and elucidated from Lecanicillium aphanocladii E4.5 compounds were isolated and elucidated from Trichoderma harzianum R5-1,including 5 terpenoids(T1-1 ~T1-5),1 lactone(T1-6)and 1 steroid(T1-7).The next step was to assay the compounds for their anti-bacterial and anti-microalgal activities.The results showed that P1-10 displayed moderate anti-bacterial activity against Bacillus subtilis and B.anthracis at 20 ?g/disk,and the diameters of inhibition zones were 15.3 mm and 15.7 mm,respectively.Compounds T1-1~T1-5 showed inhibitory effect on Vibrio anguillarum,and the diameters of inhibition zones of T1-1 and T1-5 were 11.4 mm and 10.3 mm,respectively.However,both of them had no inhibitory activity for V.splendidus and V.harveyi.The results of anti-microalgal activity showed that P1-9 and P1-10 possessed significant inhibitory activity on Chattonella marina,whose inhibition rates were 91.4% and 97.3%,respectively,at 100 ?g/mL.P1-12 showed inhibitory activity against Heterosigma akashiwo and C.marina,and the inhibition rates were 97.1% and 100%,respectively.The systemic study on the secondary metabolites of three sediment-derived fungi has not only enriched the research of marine natural products but provided the basis for the study of secondary metabolites from some rare fungi.