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吴凤锷 《高等学校化学学报》1985,6(5):427
液体柱色谱是现代分离有机化合物的主要手段。但此法耗费溶剂多,溶剂在下滴过程中污染空气,回收洗出液的工作量大。索氏脂肪提取器(Soxhletextractor)用于提取某些组分,耗费溶剂少,操作方便。有人用索氏提取器分离马兜铃酸,取得较好效果。但与液体柱色谱相比,索氏提取器的分离效果很差。粗短尾析柱的广泛使用,取得了不少经验。我们对比这两种分离方法的优缺点以后,发现可以把二者结合起来。为此,设计了一种新的装置,取名为回流层析柱。它具有液体柱色谱及索氏提取器的优点。 相似文献
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对比酸水浸提法、醇提取法、索氏提取法的提取率,探讨博落回中总生物碱的最佳提取方法。从提取率、生物碱含量、有机溶剂消耗方面对酸水浸提提、乙醇提取以及索氏提取等方法的比较得出以下结论:索氏提取法中有机溶剂的回收率是最高的,酸水浸提法次之,醇提取法对原料的利用率相对来说是最低的。 相似文献
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反相高效液相色谱法测定人参皂甙Compound-K的含量 总被引:5,自引:0,他引:5
人参皂甙compound-K(C-K)在人参中的含量极低,但它是其他含量较高的人参皂甙Rb1和Rb2等在人体肠道内的主要
降解产物和最终吸收形式,具有很高的生物活性。采用反相高效液相色谱法测定了人参总皂甙发酵液中C-K的含量。色谱
条件为:反相C18柱;乙腈-水(体积比为48∶52)溶液为流动相,流速1.0 mL/min;紫外检测波长203 nm;柱温35 ℃;外标法
定量。结果表明:C-K的质量浓度为0.05~0.8 g/L时,其峰面积与质量浓度具有良好的线性关系,相关系数为0.9998。方法
的检测限(S/N=3)为2.5 mg/L,峰面积测定值的相对标准偏差(n=6)为2.20%。测定栽培人参总皂甙及三七茎叶总皂甙微生
物发酵液中C-K的平均加标回收率(n=3)分别为98.6%和99.7%。该方法快速简便,准确可靠,可用于C-K的制备研究及药物
开发。 相似文献
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中药刺五加叶中有效成分的几种微波辅助提取方法研究 总被引:13,自引:0,他引:13
利用高压微波提取法、常压回流微波提取法、流动微波提取法和索氏提取法提取中药刺五加中黄酮和皂苷类化合物,考察各种提取方法提取效率随时间的变化。结果表明,高压微波提取法在压力为300kPa,完全提取的时间为10min;常压回流微波提取法完全提取的时间为14min;流动微波提取法完全提取的时间为10min;索氏提取法需8h尚能完成。各种提取方法总黄酮的提取率分别为43.7、48.2、42.7和34.7mg/g;总皂苷的提取效率分别为60.2、61.5、59.8和46.5mg/g。与索氏提取法比较,微波提取法提取黄酮和皂苷,提取时间大大缩短,且提取效率显著提高。 相似文献
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西洋参(Panax quinquefolius L.)有降压、降血糖、提高免疫力的作用~([1]),对神经系统、心血管系统均有良好的调节作用,对心律失常有明显的预防和治疗作用~([2]).西洋参的主要有效成分为人参皂苷,同时还含有挥发油、氨基酸、多糖和微量元素等~([3]).近年来,索氏抽提法、超声波辅助萃取法、微波辅助萃取法、超临界萃取法等方法都广泛应用于人参根中人参皂苷的提取~([4]).本研究采用超声提取,将泡沫浮选与固相提取结合只需称取少量西洋参根样品就可分离测定西洋参根中的常见人参皂苷. 相似文献
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用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%. 相似文献
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The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula. 相似文献
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Rebecca J. Burton Mandy L. CrowtherNeal J. Fazakerley Shaun M. FilleryBarry M. Hayter Jason G. KettleCaroline A. McMillan Paula PerkinsPeter Robins Peter M. SmithEmma J. Williams Gail L. Wrigley 《Tetrahedron letters》2013
The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines. 相似文献
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Regiospecific and direct imidation of the methyl C(sp3)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products. 相似文献
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《Tetrahedron》2014,70(21):3377-3384
The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative. 相似文献
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Scope of the copper catalyzed/mediated selenium-nitrogen coupling reaction has been studied for the synthesis of isoselenazolones. It is noticed that the 2-chloro, 2-bromo-, and 2-iodo-aryl amides substrates can be exploited in the selenium-nitrogen coupling reaction by employing 25-100 mol % of CuI/1,10-phenanthroline (L) and potassium carbonate as a base in DMF. Furthermore, electron rich 2-chloro-arylamides also underwent selenium-nitrogen coupling reaction to give biologically important selenium-nitrogen heterocycles. Also, copper-catalyzed selenium-nitrogen coupling reaction has been meticulously applied for the synthesis of diaryl diselenides having methoxy, amine, and amide functionality from respective aryl iodides in the presence of stoichiometric amount of succinimide as an external Se-N coupling partner. 相似文献
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Hao Xu Liyang Pan Xiaomin Fang Baoying Liu Wenkai Zhang Minghua Lu Yuanqing Xu Tao Ding Haibo Chang 《Tetrahedron letters》2017,58(24):2360-2365
A series of novel N-methyl morpholine (Nmm) based ionic liquids with 1,2-propanediol group were synthesized and used as catalysts for Knoevenagel condensation at room temperature in water. Under the effect of the catalyst, various aldehydes or aliphatic ketones could react with a wide range of activated methylene compounds well, including malononitrile, alkyl cyanoacetate, cyanoacetamide, β-diketone, barbituric acid, 2-arylacetonitrile and thiazolidinedione. Furthermore, most of the products could be separated just by filtrating and washing with water. Additionally, the catalyst is recyclable and applicable for the large-scale synthesis. 相似文献
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A series of polyheterocyclic spirotetrahydrothiophene derivatives were obtained in moderate to excellent yields via a catalyst-free sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 under mild conditions. We also present the first asymmetric sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 with moderate to good enantioselectivities catalyzed by readily available chiral phase-transfer catalysts (PTCs). 相似文献
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Andrey A. BerezinPanayiotis A. Koutentis 《Tetrahedron》2011,67(22):4069-4078
Both soluble guanylate cyclase (sGC) inhibitors ODQ 1 and NS2028 2 are synthesized via improved protocols. In the former case treating 3,4-dihydroquinoxalin-2(1H)-one oxime 8, which can be prepared in two steps from 1,2-benzenediamine, with 1,1′-carbonyldiimidazole (CDI) gives the dihydro-ODQ 10 that in the presence of KMnO4 oxidises to give ODQ 1 in an overall yield of 46% starting from 1,2-benzenediamine. In the latter case, the synthesis affords NS2028 2 from 2-amino-4-bromophenol 3 in three steps with an overall yield of 85% and avoids the need for chromatography. Furthermore, Suzuki-Miyaura reaction conditions are described that enable the preparation of 8-aryl and 8-heteroaryl derivatives of NS2028 directly from NS2028 2. Finally, demethylation of the 8-(methoxyphenyl) substituted analogues afforded the 8-(hydroxyphenyl) derivatives 40-42. All new products are fully characterised. 相似文献