Investigation of the cultured mycelia of Cordyceps ophioglossoides resulted in the isolation and characterization of three new unusual spiro[4.5]decane sesquiterpenes, cordycepol A ( 1 ), cordycepol B ( 2 ), and cordycepol C ( 3 ), and a new fumagillol analogue, cordycol ( 4 ). Their structures were established by spectroscopic means. The cytotoxic activities were also evaluated, compounds 3 and 4 showing their IC50 values in the range of 12–33 μg/ml against HeLa and HepG2 (Table 3). In addition, 3 and 4 were not obviously harmful towards normal liver cell lines LO2, showing IC50 values above 80 μg/ml. 相似文献
Chemical investigation on the stem and root of Melicope pteleifolia afforded three new prenylated benzene metabolites as racemic mixtures, named pteleifolins A–C ( 1 – 3 , resp.). Their gross structures were elucidated on the basis of spectroscopic analysis, especially 2D‐NMR experiments. An enantiomer resolution of (±)‐ 1 using chiral HPLC was performed, and the absolute configuration of the enantiomers were determined to be (+)‐(S)‐ 1 and (?)‐(R)‐ 1 by means of circular‐dichroism analysis. 相似文献
Two types of β‐enaminoketone derivatives of 3‐(2‐oxo‐2‐arylethylidene)‐3,4‐dihydro‐1H‐quinoxalin‐2‐ones and 3‐(2‐oxo‐2‐arylethylidene)‐3,4‐dihydro‐benzo[1,4]oxazin‐2‐ ones were effectively and conveniently prepared in good to excellent yields under solvent‐free conditions via the catalysis of sulfamic acid in the corresponding condensations of o‐phenylenediamine and o‐aminophenol with ethyl 2,4‐dioxo‐4‐arylbutyrate respectively. The compounds were confirmed by IR, 1H NMR, and 13C NMR, and a representative was further determined by X‐ray crystallography. 相似文献
A green and highly efficient method for the synthesis of polyfunctionalized indoline‐spiro fused pyran derivatives has been established. This reaction was conducted by reacting readily available and inexpensive starting materials, such as isatins, cyclic‐1,3‐dicarbonyl compounds, and malononitrile in aqueous media without any catalysts under microwave irradiation. The present green synthesis shows fascinating properties such as the use of water as the reaction solution, concise one‐pot conditions, short reaction periods (8–14 min), and easy purifications. The synthesis could also set a good example to GAP (Group‐Assistant‐Purification) chemistry in which purification via chromatography can be avoided and the pure products can be easily acquired only by washing the crude products with 95% EtOH. 相似文献
We have developed a method for in-situ construction of a porous network-like silver film on the surface of a glassy carbon electrode (GCE). It is based on a galvanic replacement reaction where a layer of copper nanoparticles is first electrodeposited as a sacrificial template. The silver film formed possesses a porous network-like structure and consists of an assembly of numerous nanoparticles with an average size of 200 nm. The electrode displays excellent electrocatalytic activity, good stability, and fast response (within 2 s) toward the reduction of nitrate at a working potential of −0.9 V. The catalytic currents linearly increase with the nitrate concentrations in the range of 0.08–6.52 mM, with a detection limit of 3.5 μM (S/N = 3) and a repeatability of 3.4 % (n = 5).
We have prepared porous and network-like nanofilms of gold by galvanic replacement of a layer of copper particles acting as a template. The films were first characterized by scanning electron microscopy and X-ray diffraction, and then modified with cysteamine so to enable the covalent immobilization of the enzyme microperoxidase-11. The immobilized enzyme undergoes direct electron transfer to the underlying electrodes, and the electrode displays high electrocatalytic activity towards the reduction of oxygen and hydrogen peroxide, respectively, owing to the largely enhanced electroactive surface of the porous gold film. The detection limit of H2O2 is 0.4 μM (3 S/N).
Figure
In this work, porous network-like Au films were prepared by galvanic replacement using Cu film as a sacrificial template. The cysteamine modified Au film was used to immobilize microperoxidase-11, which showed good stability and excellent electrochemical performance towards the reduction of O2 and H2O2, respectively 相似文献
Granular nanowires with a diameter of about 60 nm were fabricated from cuprous oxide (Cu2O) by an electrochemical method using anodic aluminium oxide as the template. A non-enzymatic sensor for hydrogen peroxide (H2O2) was then developed on the basis of a gold electrode modified with Cu2O nanowires and Nafion. The resulting sensor enables the determination of H2O2 with a sensitivity of 745 μA?mM?1?cm?2, over a wide linear range (0.25 μM to 5.0 mM), and with a low detection limit (0.12 μM). The results demonstrate that the use of such granular nanowires provides a promising tool for the design of non-enzymatic chemical sensors.
Figure
A non-enzymatic sensor for hydrogen peroxide (H2O2) was developed on the basis of a gold electrode modified with Cu2O nanowires and Nafion. The resulting sensor enables the determination of H2O2 with a sensitivity of 745 μA mM?1 cm?2, over a wide linear range (0.25 μM to 5.0 mM), and with a low detection limit (0.12 μM). The results demonstrate that the use of such granular nanowires provides a promising tool for the design of non-enzymatic chemical sensors 相似文献
The thermal stability and kinetics of isothermal decomposition of diosgenin were studied by thermogravimetry (TG) and Differential Scanning Calorimeter (DSC). The activation energy of the thermal decomposition process was determined from the analysis of TG curves by the methods of Flynn-Wall-Ozawa, Doyle, ?atava-?esták and Kissinger, respectively. The mechanism of thermal decomposition was determined to be Avrami-Erofeev equation (n = 1/3, n is the reaction order) with integral form G(α) = [?ln(1 ? α)]1/3 (α = 0.10–0.80). Ea and logA [s?1] were determined to be 44.10 kJ mol?1 and 3.12, respectively. Moreover, the thermodynamics properties of ΔH≠, ΔS≠, and ΔG≠ of this reaction were 38.18 kJ mol?1, ?199.76 J mol?1 K?1, and 164.36 kJ mol?1 in the stage of thermal decomposition. 相似文献