No abstract

No abstract

A new polyketide, 2-(7′-hydroxyoxooctyl)-3-hydroxy-5-methoxybenzeneacetic acid ethyl ester (1), together with three known compounds dothiorelone A (2), B (3), and C (4) were isolated from the mangrove endophytic fungus Phomopsis sp. ZSU-H76 obtained from the South China Sea. Their structures were elucidated by spectroscopic methods, mainly 1D and 2D NMR spectroscopic techniques. Primary bioassays showed that 1 exhibited cytotoxicity against HEp-2 and HepG2 cells with IC 50 values of 25 and 30 μg/mL, respectively.Marine-derived fungi have proven to be a rich source of structurally unique and biologically active secondary metabolites [1]. In our search for new metabolites from marine-derived mangrove endophytic fungi from the South China Sea, we have isolated many significant new bioactive metabolites [2][3][4][5][6][7][8]. This paper reports the isolation and characterization of a new polyketide, 2-(7′-hydroxyoxooctyl)-3-hydroxy-5-methoxybenzeneacetic acid ethyl ester (1), and three known compounds dothiorelone A (2), B (3), and C (4) from the mangrove endophytic fungus Phomopsis sp. ZSU-H76 isolated from the stem of the mangrove tree Excoecaria agallocha from Dong Zai, Hainan, China. Cytotoxic effects of compound 1 against HEp-2 cells and HepG2 cells were first measured.The ethyl acetate extract of a fermentation broth of the fungus was repeatedly chromatographed on silica gel using gradient elution from petroleum to ethyl acetate to give compound 1 from the 15% ethyl acetate/petroleum fraction as a colorless oil. Compound

High-performance polyimide fibers possess many excellent properties, e.g., outstanding thermal stability and mechanical properties and excellent radiation resistant and electrical properties. However, the preparation of fibers with good mechanical properties is very difficult. In this report, a biphenyl polyimide from 3,3Ј,4,4Ј-biphenyltetracarboxylic dianhydride and 4,4Ј-oxydianiline is synthesized in p-chlorophenol by one-step polymerization. The solution is spun into a coagulation bath of water and alcohol via dry-jet wet-spinning technology. Then, the fibers are drawn in two heating tubes. Thermal gravimetric analysis, thermal mechanical analysis, and dynamic mechanical analysis (DMA) are performed to study the properties of the fibers. The results show that the fibers have a good thermal stability at a temperature of more than 400°C. The linear coefficient of thermal expansion is negative in the solid state and the glass transition temperature is about 265°C. DMA spectra indicate that the tan␦ of the fibers has three transition peaks, namely, ␣, ␤, and ␥ transition. The ␣ and ␥ transition temperature, corresponding to the end-group motion and glass transition, respectively, extensively depends on the applied frequency, while the ␤ transition does not. The activation energy of ␣ and ␥ transition is calculated using the Arrhenius equation and is 38.7 and 853 kJ/mol, respectively.

No abstract