| Fungi derived from special ecological niches such as deep sea, craters, hyper-saline waters,tropical forests and deserts, gain prominence as a source of novel bioactive compounds.Coastal saline soil, as a unique ecological environment, provides a habitat for some specialfungi, and remains largely unexplored. Fungi from this habitat may develop a unique metabolicmechanism during the long process of evolution owing to high-salt and high-pH livingcondition, and may produce secondary metabolites with novel structures. In this paper, apreliminary study has been launched on the diversity of fungi derived from coastal saline soilin Zhanhua (Shandong province) located in Yellow River Dellta. By integrated biological andchemical screening methods, five fungi derived from coastal saline soil were obtained and weinitiated a program to discover bioactive natural products from the five fungi.1. Study on diversity and activities (antimicrobial and antitumor activity) ofsymbiotic fungi derived from coastal saline soil in Yellow River Dellta.More than30samples collected from coastal saline soil in Zhanhua (Shandong province)located in Yellow River Dellta have been chosen for investigation. Fungal strains were definedby methods combined with morphologic traits, physiological and biochemical characteristicsand molecular biological analysis.26fungi, belonging to eight genera in six orders, have beenisolated and identified, and phylogenetic trees have been built using Mega5.0.The results of antimicrobial and antitumor activity revealed that about46.5%of allisolated fungi had inhibition (φ≥8mm)to at least one of the tested bacterial. About30.7%oftested fungi had inhibition to A549at the concentration of50μg/mL.By integrated biological and chemical screening (HPLC-DAD) methods, five fungiderived from coastal saline soil were obtained for the next study of active secondarymetabolites. 2. Study on secondary metabolites of five fungi.The five strains were fermented separately and the extracts were isolated by various kindsof column chromatographies on silica gel, Sephadex LH20, and recycling preparative HPLC.The structures of the isolated compounds were elucidated by the physicochemical charactersand spectral analysis, such as UV, IR, NMR, MS, X-ray, etc. Sixteen compounds including onenew bridged ring compound, along with other fifteen known compounds belonged tonortriterpenoid, indole alkaloids, diketopiperazine alkaloids and steroids, were isolated fromAspergillus fumigates JH43. Eleven compounds including two new diphenyl ether derivatives,along with other nine known compounds including diphenyl ethers, anthraquinones andphenols. Eleven known compounds including diketopiperazine alkaloids, pyrimidine,butenolides, sesterterpenoids and steroids were isolated from Penicillium janthinellum KL24.Eight known compounds including furancarboxylic acids, benzoic acids, anthraquinones andditetrahydroxathones were isolated from Aspergillus aculeatus WD5, and secalonic acid F wasthe dominant secondary metabolite under the presented fermentation conditions. Ten knowncompounds including steroids, benzoic acids, phenols, anthraquinones, carboxylic acids andlactones and diketopiperazine alkaloids, were isolated from Aspergillus clavatonanicus WD8.Three new compounds (aspergiketone, iizukae A and iizukae B) were evaluated for theirantimicrobial and antitumor activities. Iizukae A exhibited weak antibacterial activity againststaphylococcus aureus, Staphylococcus and Escherichia coli with the IC50values of34.6,85.4and67.8μM, respectively. Both iizukae A and iizukae B showed weak cytoloxicity againstHL-60, A-549and BEL-7402.3. Preliminary study on the antitumor effect and mechanism of SAF.In this paper, the antitumor activity and the related mechanism of SAF on hepatocellularcarcinoma were studied for the first time. SAF could inhibit the proliferation of HepG2cellline with an IC50value of6.8μM in a dose-and time-dependent manner.Apoptosis rate of HepG2cells treated with SAF was determined by Annexin V/PI doublestaining of flow cytometry. At dose of6.8μM/L after48h, SAF could significantly induceHepG2cell apoptosis. The mechanism might be associated with promoting cell apoptosis byinducing generating of intracellular ROS. The tumor-bearing H22mouse modle was established. The inhibitory rates in the groupstreated with SAF at50mg/kg were94.74%, superior to the positive (5-FU) rate of the tumor70.33%and could increase mice thymus and spleen index at dose of10mg/kg, which indicatedthat SAF could improve the body′s immune function in vivo.In conclusion, in presented paper the preliminary study of diversity of fungi derived fromcoastal saline soil in Yellow River Dellta and their antimicrobial and antitumor activities havebeen studied for the first time together with the phylogenetic tree of the isolated fungi havebeen built. Three new compounds were isolated from five fungi derived from this special nich.The antitumor activity and mechanism of SAF produced by Aspergillus aculeatus wereelementarily discussed in the article. The result revealed that SAF could significantly induceHepG2cell apoptosis. The mechanism might be associated with promoting cell apoptosis byinducing generating of intracellular ROS. The research also provides evidences that SAF havean anti-tumor activity in vivo and enhances the function of immunological cells. All theseresults provide promising resource fungi with antitumor and antimicrobial activity and lay afoundation for the research for anticancer drugs. |
