共查询到20条相似文献,搜索用时 46 毫秒
1.
2.
3.
4.
从无毛狭叶香茶菜(Isodonangustifoliusvar.glabrescensH.W.Li)中分离得到4个已知二萜化合物;7-乙酰基-鲁山冬凌草甲素,鲁山冬凌草甲素,乙素和紫萼香茶菜甲素,经二维核磁共振波谱(2D-NMR)解析表明,它们的结构分别由先前报道的5、6、7和8应修订为结构1,2,3和4。 相似文献
5.
6.
冬凌草中一新的二萜成分--冬凌草辛素 总被引:4,自引:0,他引:4
从河南省鹤壁地区产冬凌〖Isodon rubescens(Hemsl.)Hara〗叶中分得一个新地二萜化合物,命名为冬凌草辛素(Rubescensin H)〈经NMR谱等确定其结构为6β,7β,14β,15R-四羟基-11β-甲酰氧基-7α,20-环氧-对映-贝壳杉-16-烯。 相似文献
7.
紫萼香茶菜甲素的结构 总被引:2,自引:1,他引:1
从紫萼香茶菜叶的乙醚提取物中分得一个新的二萜化合物,命名为紫萼香茶菜甲素(rabdoforrestin A),根据波谱和化学证据,其结构为对映-11β-羟基-2α,3α,6β,7α-四乙酰氧基-16-贝壳杉烯-15-酮(ent-11β-hydroxy-2α,3α,6β,7α-tetraacetoxy-16-kauren-15-one)。另外还分离到已知黄酮化合物线蓟素(cirsilioi 4)。 相似文献
8.
9.
冬凌草水溶性化学成分研究 总被引:16,自引:1,他引:15
新鲜冬凌草用70%丙酮水溶液组织破碎提取,然后经Diaion HP-20、Toyopearl HW-40、MCI Gd、silica gel等柱层析方法分离得到5个单体化合物,经波谱分析鉴定为α-D-呋喃果糖(1),阿魏酸(2),丹参素甲正丁酯(3),3,4-二羟基苯乳酸(4),延命素-1β-D-吡喃葡萄糖苷(5)。除延命素-1β-D-吡喃葡萄糖苷外,其它4个化合物均为首次从冬凌草及其同属植物中分离得到。 相似文献
10.
11.
Plasmalogen is a major phospholipid of mammalian cell membranes. Recently it is becoming evident that the sn-1 vinyl-ether linkage in plasmalogen, contrasting to the ester linkage in the counterpart diacyl glycerophospholipid, yields differential molecular characteristics for these lipids especially related to hydrocarbon-chain order, so as to concertedly regulate biological membrane processes. A role played by NMR in gaining information in this respect, ranging from molecular to tissue levels, draws particular attention. We note here that a broad range of enzymes in de novo synthesis pathway of plasmalogen commonly constitute that of diacyl glycerophospholipid. This fact forms the basis for systematic crosstalk that not only controls a quantitative balance between these lipids, but also senses a defect causing loss of lipid in either pathway for compensation by increase of the counterpart lipid. However, this inherent counterbalancing mechanism paradoxically amplifies imbalance in differential effects of these lipids in a diseased state on membrane processes. While sharing of enzymes has been recognized, it is now possible to overview the crosstalk with growing information for specific enzymes involved. The overview provides a fundamental clue to consider cell and tissue type-dependent schemes in regulating membrane processes by plasmalogen and diacyl glycerophospholipid in health and disease. 相似文献
12.
黄牛木属植物的化学成分与生物活性研究进展 总被引:1,自引:0,他引:1
本文综述了从1963年以来黄牛木属植物的化学成分和生物活性研究,概括了该属植物中部分口山酮和蒽醌化合物的NMR数据。 相似文献
13.
Jean-Pierre Girault Catherine Blais Philippe Beydon Christian Rolando Ren Lafont 《Archives of insect biochemistry and physiology》1989,10(3):199-213
Several 3-dehydro- (or 3-oxo-) ecdysteroids have been prepared by enzymatic and/or chemical means. Methods for their purification using various high-performance liquid chromatography systems are described. Proton and carbon nuclear magnetic resonance analyses show that 3-dehydroecdysteroids when dissolved in water or methanol (but not in chloroform) present a temperature-dependent equilibrium between two forms. The possible structure of these two forms is discussed. 相似文献
14.
珙桐叶中喹啉类生物碱甙——pumiloside结构鉴定 总被引:2,自引:0,他引:2
首次从珙桐叶甲醇提取物的水溶性部分得到一配糖体化合物-喹啉类生物碱甙(pumiloside),它是抗肿瘤物质喜树碱的生物合成前体。本文对其结构进行鉴定。 相似文献
15.
16.
High-throughput screening (HTS) using NMR spectroscopy has become a common component of the drug discovery effort and is widely used throughout the pharmaceutical industry. NMR provides additional information about the nature of small molecule-protein interactions compared to traditional HTS methods. In order to achieve comparable efficiency, small molecules are often screened as mixtures in NMR-based assays. Nevertheless, an analysis of the efficiency of mixtures and a corresponding determination of the optimum mixture size (OMS) that minimizes the amount of material and instrumentation time required for an NMR screen has been lacking. A model for calculating OMS based on the application of the hypergeometric distribution function to determine the probability of a hit for various mixture sizes and hit rates is presented. An alternative method for the deconvolution of large screening mixtures is also discussed. These methods have been applied in a high-throughput NMR screening assay using a small, directed library. 相似文献
17.
Summary The resolution of spectral frequencies in NMR data obtained from discrete Fourier transformation (DFT) along D constant-time dimensions can be improved significantly through extrapolation of the D-dimensional free induction decay (FID) by multidimensional Bayesian analysis. Starting from Bayesian probability theory for parameter estimation and model detection of one-dimensional time-domain data [Bretthorst, (1990) J. Magn. Reson., 88, 533–551; 552–570; 571–595], a theory for the D-dimensional case has been developed and implemented in an algorithm called BAMBAM (BAyesian Model Building Algorithm in Multidimensions). BAMBAM finds the most probable sinusoidal model to account for the systematic portion of any D-dimensional stationary FID. According to the parameters estimated by the algorithm, the FID is extrapolated in D dimensions prior to apodization and Fourier transformation. Multidimensional Bayesian analysis allows for the detection of signals not resolved by the DFT alone or even by sequential one-dimensional extrapolation from mirror-image linear prediction prior to the DFT. The procedure has been tested with a theoretical two-dimensional dataset and with four-dimensional HN(CO)CAHA (Kay et al. (1992) J. Magn. Reson., 98, 443–450) data from a small protein (8 kDa) where BAMBAM was applied to the 13C and H constant-time dimensions.To whom correspondence should be addressed. 相似文献
18.
Reimond Bernstein Christian Cieslar Alfred Ross Hartmut Oschkinat Jens Freund Tad A. Holak 《Journal of biomolecular NMR》1993,3(2):245-251
Summary An algorithm based on the technique of combinatorial minimization is used for the semi-automated assignment of multidimensional heteronuclear spectra. The program (ALFA) produces the best assignment compatible with the available input data. Even partially misleading or missing data do not seriously corrupt the final assignment. Ambiguous sequences of the possible assignment and all alternatives are indicated. The program can also use additional non-spectroscopic data to assist in the assignment procedure. For example, information from the X-ray structure of the protein and/or information about the secondary structure can be used. The assignment procedure was tested on spectra of mucous trypsin inhibitor, a protein of 107 residues. 相似文献
19.