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151.
Transformation of arctiin to estrogenic and antiestrogenic substances by human intestinal bacteria 总被引:2,自引:0,他引:2
Xie LH Ahn EM Akao T Abdel-Hafez AA Nakamura N Hattori M 《Chemical & pharmaceutical bulletin》2003,51(4):378-384
After anaerobic incubation of arctiin (1) from the seeds of Arctium lappa with a human fecal suspension, six metabolites were formed, and their structures were identified as (-)-arctigenin (2), (2R,3R)-2-(3',4'-dihydroxybenzyl)-3-(3",4"-dimethoxybenzyl)butyrolactone (3), (2R,3R)-2-(3'-hydroxybenzyl)-3-(3",4"-dimethoxybenzyl)butyrolactone (4), (2R,3R)-2-(3'-hydroxybenzyl)-3-(3"-hydroxy-4"-methoxybenzyl)butyrolactone (5), (2R,3R)-2-(3'-hydroxybenzyl)-3-(3",4"-dihydroxybenzyl)butyrolactone (6), and (-)-enterolactone (7) by various spectroscopic means including two dimensional (2D)-NMR, mass spectrometry, and circular dichroism. A possible metabolic pathway was proposed on the basis of their structures and the time course of the transformation. Enterolactones obtained from the biotransformation of arctiin and secoisolariciresinol diglucoside (SDG, from the seeds of Linum usitatissium) by human intestinal bacteria were proved to be enantiomers, with the (-)-(2R,3R) and (+)-(2S,3S) configurations, respectively. Compound 6 showed the most potent proliferative effect on the growth of MCF-7 human breast cancer cells in culture among 1 and six metabolites, while it showed inhibitory activity on estradiol-mediated proliferation of MCF-7 cells at a concentration of 10 microM. These results indicate that the transformation of 1 by intestinal flora might be essential for the manifestation of the estrogenic and antiestrogenic activity of 1. 相似文献
152.
由聚苯胺粒子组成的电流变液的研究 总被引:6,自引:1,他引:6
由经碱处理的掺杂态聚苯胺(PAn)制得高介电常数的半导体PAn粒子,将其悬浮于电绝缘油可组成电流变液,讨论了电流变(ER)液的静态屈服应力(τ_s),电流密度等性能与PAn的介电常数(ε_p),导电率(σ),体积分数和应用电场强度的关系。对导电率相同的PAn粒子,用氨水处理的PAn粒子ε_p较用NaOH液处理的高,前者在σ足够低如σ≤1.0×10 ̄(-7)/cm时,ER液的τ_s随偶极系数的平方(β ̄2)的增大而呈现非线性增加;后者ER液的τ_s随β ̄2的增大出现一最大值.结果表明:由聚苯胺粒子可组成高电流变活性的无水ER液. 相似文献
153.
The piezoelectric quartz crystal (PQC) impedance technique was applied to monitor in situ generation and precipitation of the ferric hydroxide sol in aqueous solutions at 90 degrees C. Equivalent circuit parameters and resonant frequencies as well as the half-peak width of the electroacoustic conductance spectrum deltaf(G1/2) for the PQC resonance were obtained and analyzed. Three stages, sol generation and simultaneous adsorption, adsorption equilibrium, and precipitation of ferric hydroxide sol could be identified in the process of adding the ferric nitrate solution into the hot water. A scheme of two consecutive reactions occurring at the electrode/solution interface was used to analyze the adsorption kinetics of ferric hydroxide sol onto the Au electrode. In addition, the electrolyte-induced precipitation of the colloid was monitored and discussed. Temperature effect on the PQC resonance behavior in liquid was also investigated. Since the PQC impedance technique provides multidimensional piezoelectric information in situ, it is highly recommended for studying the process of sol-gel generation and precipitation. Copyright 2001 Academic Press. 相似文献
154.
155.
库仑滴定法测定有机硅样品中的氮含量 总被引:3,自引:0,他引:3
本文利用库仑滴定法研究了高分子和低分子硅氮化合物及含氮有机硅样品中氮含量的测定,并研究和讨论了影响测定结果准确性的因素。 相似文献
156.
Microcapsules containing healing agents have been used to develop the self-healing polymeric composites. These microcapsules
must possess special properties such as appropriate strength and stability in surrounding medium. A new series of microcapsules
containing dicyclopentadiene (DCPD) with melamine–formaldehyde (MF) resin as shell material were synthesized by in situ polymerization
technology. These microcapsules may satisfy the requirements for self-healing polymeric composites. The chemical structure
of microcapsule was identified by using Fourier transform infrared (FTIR) spectrometer. The morphology of microcapsule was
observed by using optical microscope (OM) and scanning electron microscope. Size distribution and mean diameter of microcapsules
were determined with OM. The thermal properties of microcapsules were investigated by using thermogravimetric analysis and
differential scanning calorimetry. Additionally, the self-healing efficiency was evaluated. The results indicate that the
poly(melamine–formaldehyde) (PMF) microcapsules containing DCPD have been synthesized successfully, and their mean diameters
fall in the range of 65.2∼202.0 μm when the adjusting agitation rate varies from 150 to 500 rpm. Increasing the surfactant
concentration can decrease the diameters of microcapsules. The prepared microcapsules are thermally stable up to 69 °C. The
PMF microcapsules containing DCPD can be applied to polymeric composites to fabricate the self-healing composites. 相似文献
157.
Xianmei Xie Xiurong Ren Jinping Li Xiaojun Hu Zhizhong Wang 《天然气化学杂志》2006,15(2):100-104
Ultrasonic technology has been intensively studied recently due to its special features. In this paper, an ultrasonic crystallization method was introduced for the preparation of ZnAl-Hydrotalcite-Like compounds (ZnAl-HTLcs). Samples with high crystallinity, small particle size and narrow particle size distribution were obtained and fully characterized using conventional techniques of XRD, FT-IR and TGDTA. The results prove that both ultrasonic frequency and ultrasonic power have effects on the sizes of the product particles. By varying the ultrasonic power from 250 W to 88 W, with the ultrasonic frequency fixed at 59 kHz, the median particle size of the samples increased from 0.37 μm to 0.82 μm. By altering the hydrothermal treatment time from 1 h to 5 h at 110℃, the median particle size of ZnAl-HTLcs synthesized via ultrasonic crystallization increased from 0.88 μm to 1.11 μm. 相似文献
158.
Here we report the formation and spectroscopic properties of cadmium sulfide (CdS) nanocrystal systems: individual nanocrystal and CdS aggregates. The optical absorption and luminescence spectra of the aggregated CdS nanocrystals and individual nanocrystal show exciton aggregate and individual exciton characteristics. Although it is not Bose-Einstein condensation, such aggregated quantum dots (QDs) seem to supply us opportunity to study the interactions and condensation of excitons in multi-QDs system, not in the separated QDs system. 相似文献
159.
The drug-loaded alginate/poly-L-arginine/chitosan ternary complex microcapsules were prepared by mixing method, absorption method and the combined method of mixing and absorption, respectively. The effect of drug-loading methods on drug load, the encapsulation efficiency and the release properties of the complex microcapsules were investigated. The results showed that the absorption process is a dominating factor to greatly increase the drug load of Hb into microcapsules. Upon loading Hb into microcapsules by combined method of mixing and absorption, the drug load (19.9%) is up to the maximum value, and the encapsulation efficiency is 93.8%. Moreover, the drug release is a zero-order kinetics process for the ternary complex microcapsules made by mixing. For the complex microcapsules made by absorption, the drug release is a first-order kinetics. However, for the complex microcapsules made by combining the mixing and the absorption, the drug release obeys a first-order kinetics during the first eighteen hours, changing afterwards to a zero-order kinetics process. Effect of drug-loading methods on drug load and encapsulation efficiency of alginate/poly-L-arginine/chitosan ternary complex microcapsules. 相似文献
160.
A kind of aziridine crosslinkers was synthesized and used to crosslink acrylate copolymers. The crosslinkingproperties and curing kinetics of the resin were studied. It was found that with the increase of the content of crosslinker in theemulsion, the mechanical properties and solvent resistance of the resin will be apparently improved, but its glass transitiontemperature (T_g) is very low. The lowest amount of crosslinker used in the acrylic resin emulsion is 0.25%. Curing kineticsstudied by DSC show that this curing reaction occurs readily because the apparent activation energy of the reaction is low(65.1 kJ/mol). These results demonstrate that the aziridine crosslinker is indeed a low temperature crosslinking agent and canbe used at room temperature. 相似文献