Studies On The Halo- Metabolites From One Marine Strain

Many of marine fungi, living in the special environment abundant of halide ions, can take advantage of halide ions to synthetic halogenated secondary metabolites. They have been considered as an important class of producers of halogenated secondary metabolites. Because of novel chemical structures and strong biological activities, halo-compounds have great value in pharmacology application. In order to explore the potential metabolism of marine fungus to synthesize halo-compounds, we use "salt stress" strategy to activate the metabolic pathways of fungi by adding halo-salt and optimizing culture conditions to produce new halogenated compounds. Studies in this dissertation include comparison of 4 marine fungi metabolites by adding different halogen salt, choosing target strains, isolating target compounds, structural analysis and preliminary evaluation of the activities of new compounds.Studies on the potential to synthesize bromo-, iodo- and fluoro- compounds by four marine fungi which produced chloro-metabolites were carried out. By adding halogen salt and optimizing their culture conditions, we found that Penicillium terrestre LM2-02 showed 1:1 isotope peaks in the HPLC-MS when sodium chloride in the medium was replaced by sodium bromide, which could induce the formation of bromo- compounds; when joining low- sodium fluoride in the medium, the Antarctic fungi Penicillium sp. PR19N-1 showed weak growth signs. In order to obtain fluoro-compounds, we chose the best culture conditions for its cell growth and metabolism. In spite of the fluorine spectrum detection found no signals, but the metabolites produced under these conditions may have some resistance activities. Therefore, these two strains were selected as the research objects finally.After changing the conditions and large-scale fermentations of the two strains, 24 compounds were isolated from ethyl acetate solvent extraction by using TLC thin layer chromatography, Sephadex LH-20 gel column chromatography, silica gel column chromatography, HPLC-UV high liquid chromatography and etc. 18 compounds (1-18) were obtained from marine fungus Penicillium terrestre LM2-02; 7 compounds (19-24) were obtained from marine fungus Penicillium sp. PR19N-1. Among them, 23 compounds (1-17, 19-24) including 4 new bromo-compounds (1-4) were identified through modern spectroscopic methods (MS, CD, UV, IR, NMR, etc.) (Figure 1).The antitumor activity against P388, A549 and HL-60 of the four new bromo-compounds was evaluated by CCK-8 and SRB methods. New compounds 2 and 3 showed weak cytotoxicities in vitro against murine leukemia P388 cell lines with inhibition rates at 27.2% and 31.3%, respectively. Antibacterial acticity of compounds 1-4 were evaluated, the results indicated that the compounds 1 and 2 showed weak inhibition against B.subtilis and S.aureus with MIC value of 0.1mg/mL.Summarily, by adding different bromine, iodine, fluoride salt to the culture medium and optimizing the fermentation conditions, 4 new bromo- compounds (1–4) and 19 known compounds were identified. Studies in this dissertation provided an experimental method for exploring the metabolic potential of marine fungi and getting more novel halogenated secondary metabolites.