首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   29篇
  免费   0篇
化学   21篇
物理学   8篇
  2022年   5篇
  2021年   3篇
  2020年   3篇
  2019年   1篇
  2018年   1篇
  2014年   1篇
  2013年   3篇
  2012年   1篇
  2010年   2篇
  2009年   3篇
  2006年   1篇
  2005年   2篇
  2000年   1篇
  1992年   1篇
  1979年   1篇
排序方式: 共有29条查询结果,搜索用时 15 毫秒
1.
A new and simple LC-MS method for analysis of flavonoids from Sambucus ebulus berry extracts was developed and validated. Successfully were quantitated seven polyphenols: epicatechin, epigallocatechin gallate, rutin, resveratrol, myricetin, quercetin, and kaempferol.

Two detectors, working in parallel, were used: photodiode-array and single quadrupole mass-detector. The mass detection was used for identification and quantification of the analytes, while the diode-array detector was as confirmation tool. The following m/z were tracked: 457.15 (epigallocatechin gallate); 289.06 (epicatechin); 609.13 (rutin); 227.05 (resveratrol); 317.0 (myricetin); 301.02 (quercetin); 285.02 (kaempferol). For optimization the chromatographic separation three wavelengths 205?nm, 305?nm, 272?nm were monitored. The method was capable to detect in one run compounds with no UV or fluorescence chromophore and with very similar structures, such as plant polyphenols. The linearity was from 0.05?mg/L to 50?mg/L (R2 0.9962–0.9987). The recoveries for all tested analytes were between 81.6% and 104.7%.

The method was applied for analysis of crude extract of Sambucus ebulus ripe fruits. Three major polyphenols – epicatechin (0.84?mg/100gFW), quercetin (0.15?mg/100gFW) and kaempferol (0.05?mg/100gFW) were identified and quantified.

The proposed method could be successfully used for routine analysis of epigallocatechin gallate, epicatechin, rutin, resveratrol, myricetin, quercetin, and kaempferol in Sambucus ebulus extracts.  相似文献   

2.
Protein glycosylation represents one of the major post-translational modifications and can have significant effects on protein function. Moreover, changes in the carbohydrate structure are increasingly being recognized as an important modification associated with cancer etiology. In this report, we describe the development of a proteomics approach to identify breast cancer related changes in either concentration and/or the carbohydrate structures of glycoprotein(s) present in blood samples. Diseased and healthy serum samples were processed by an optimized sample preparation protocol using multiple lectin affinity chromatography (M-LAC) that partitions serum proteins based on glycan characteristics. Subsequently, three separate procedures, 1D SDS-PAGE, isoelectric focusing and an antibody microarray, were applied to identify potential candidate markers for future study. The combination of these three platforms is illustrated in this report with the analysis of control and cancer glycoproteomic fractions. Firstly, a molecular weight based separation of glycoproteins by 1D SDS-PAGE was performed, followed by protein, glycoprotein staining, lectin blotting and LC–MS analysis. To refine or confirm the list of interesting glycoproteins, isoelectric focusing (targeting sialic acid changes) and an antibody microarray (used to detect neutral glycan shifts) were selected as the orthogonal methods. As a result, several glycoproteins including alpha-1B-glycoprotein, complement C3, alpha-1-antitrypsin and transferrin were identified as potential candidates for further study.  相似文献   
3.
The aim of this study is to examine seasonal changes in Cu and Co concentrations of three plant species for monitoring the effects of pollution in Elazig,Turkey.For this purpose,the leaves of the Pinus nigra L.,Cedrus libani and Cupressus arizonica together with soil samples were collected from different points depending on traffic intensity,nearness the city center and cement factory as well as control location during different months of the year.Flame atomic absorption spectrophotometer(FAAS) was used for measurement of the metals in clear digests after the dry ashing method.Copper and Co concentrations were in the ranges from 1.3to 2.6mg.kg-1 and相似文献   
4.
Thermal investigations were performed on a colony of the Colombian stingless bee Trigona (Frieseomelitta) nigra paupera by means of thermometry and direct calorimetry. A nest with about 2000 individuals was transferred to a twin calorimeter, where the bees continued their normal life and development. Two camping boxes (‘Poor Man’s Calorimeter, PMC’) with Peltier elements as cooling systems were used as a differential system. Each box had a volume of 8 L and a sensitivity of 19.2 mV W−1. The colony was monitored calorimetrically and thermometrically with resistors distributed in the nest. Signals were recorded continuously by a four-channel data logger.  相似文献   
5.
《Analytical letters》2012,45(16):2525-2533
Following optimization of extraction, separation, and analytical conditions, a simple, rapid, and sensitive HPLC-UV method was developed for the simultaneous determination of seven major bioactive components in Sambucus chinensis Lindl, including chlorogenic acid, caffeic acid, p-coumaric acid, ferulic acid, kaempferol-3-O-β-D-galactopyranoside, kaempferol-3-O-β-D-glucopyran-oside, and kaempferol-3-O-(6-actyl)-β-D-galacto-pyranoside. The good chromatographic separation was performed on a Gemini C18 reversed-phase analytical column (250 mm × 4.6 mm, 5 μm) by gradient elution with acetonitrile and formate aqueous buffer (containing 0.8% formic acid, V/V) at a flow rate of 1.0 mL/min. The detection wavelength was set at 326 nm. The intra-day and inter-day precisions were evaluated with the R.S.D. values less than 4.0%. The mean recoveries of the seven compounds were in the range of 92.4%–104.8%. The method was successfully applied to determine the seven bioactive compounds in six different origins of Sambucus chinensis Lindl samples, and there was a significant variation in the contents of the seven compounds among the six samples. Therefore, this method provided a new basis of overall assessment for routine use in the quality control of Sambucus chinensis Lindl.  相似文献   
6.
Abstract

The phytochemical examination of the polar constituents of Sambucus ebulus L. leaves led to the identification of patrinoside (1) and of a new diglycoside iridoid, patrinoside-aglycone-11-O-[β-D-glucopyranosyl-(1→6)-2′-deoxy-β-D-glucopyranoside] (trivially named as sambuloside) (2). Both of these structures have been assigned by spectroscopic means (NMR and MS).  相似文献   
7.
Synthesis of some novel fluorescence nanomaterials loaded with photoactive polyphenols originated from plants with a high spectrum of biological activity, by replacing synthetic chemicals, may open new opportunities for optical and bio-medical applications. This paper presents the synthesis, characterization and fluorescence properties of a new class of materials based on host hybrid matrices obtained through templated sol–gel route, by hydrolysis and co-condensation of tetraorthoethylsilicate with octaisobutyltetracyclo [7.3.3.15,11] octasiloxane-endo-3,7-diol. The aim of paper is focused on the evaluation of the behavior of the fluorescence properties of ornamental bush extract at immobilization in a templated silica matrix and in a silica-silsesquioxane network, using as templates a neutral, non-toxic and biodegradable surfactant from poly(ethyleneglycol) class and a high biocompatible non-surfactant from glucidic class. The proofs of ornamental bush extract entrapment by physical interactions in silica based networks were provided by FT-IR and UV–VIS spectroscopy. The changes of polymer network due to the hydrogen bond interactions between residual Si–OH groups and functional groups of organic molecules from extract were evidenced by shifts of specific vibrations. In UV–VIS-NIR domain, the chromophore groups from ornamental bush extract were also evidenced by similar small shifts. As a result of ornamental bush extract entrapment, in all the immobilized samples the fluorescence intensity was more than 10 times amplified in samples templated with poly(ethylenglycol) surfactant) and of about 5 times in samples with glucidic template due to the physical adsorption of polyphenolic molecules from extract, excellent synergistic optical properties of SiO2 and silsesquioxane compound and also due to a favorable conformational arrangement. The size of synthesized polymeric materials, estimated by dynamic light scattering technique showed main diameters less then 1.4 μm, namely 1,060 and 211 nm—for samples with d-glucose template and 1,330 and 531 nm—for samples with poly(ethyleneglycol) template, respectively, with a narrow size distribution and a polidispersity varying between 0.022 and 0.426. These results are in good accordance with TEM images that evidenced the presence of some polymeric aggregates which contain the vegetal extract immobilized inside hybrid SiO2-Sq polymeric network of about hundred nanometers size. This study bring new contributions to the development of the sol–gel procedure by entrapment of a complex vegetable mixture in polymeric matrices as integral component of silica and hybrid silica-silsesquioxane networks which leads to a significant enhancement of the functional properties of the final material, thus diversifying the potential applications of organic doped sol–gel glasses.  相似文献   
8.
Tetrahydroprotoberberines (THPBs), including (-)-stepholidine ((-)-SPD), (-)-tetrahydropalmatine ((-)-THP) and tetrahydroberberine (THB), have been demonstrated to be a new class of DA antagonists in biochemical and neuropharmacological studies. In this paper, the antagonistic action of THPBs was examined by means of single unit recording from nigral DA neuron in chloral hydrate-anesthetized and gallamine-paralyzed rats. Intravenous injection of these compounds could promptly and completely reverse the inhibition of the spontaneous firing induced by DA agonist apomorphine (APO) in a dose-dependent way. Pretreatment with (-)-SPD, (-)-THP or THB could significantly reduce the inhibitory effect of APO and shift the dose-action curve to the right. Besides, the compounds could increase the spontaneous firing of DA neurons. The above results not only strongly support the conclusion that (-)-SPD, (-)-THP and THB are DA antagonists, but also demonstrate that one of their blocking sites is at somatodendritic DA  相似文献   
9.
Sambucus nigra flowers (elderflower) have been widely used in traditional medicine for the relief of early symptoms of common cold. Its chemical composition mainly consists of polyphenolic compounds such as flavonoids, hydroxycinnamic acids, and triterpenes. Although the antioxidant properties of polyphenols are well known, the aim of this study is to assess the antioxidant and protective potentials of Sambucus nigra flowers in the human neuroblastoma (SH-SY5Y) cell line using different in vitro approaches. The antioxidant capacity is first evaluated by the oxygen radical absorbance capacity (ORAC) and the free radical scavenging activity (DPPH) methods. Cell viability is assessed by the crystal violet method; furthermore, the intracellular ROS formation (DCFH-DA method) is determined, together with the effect on the cell antioxidant defenses: reduced glutathione (GSH) and antioxidant enzyme activities (GPx, GR). On the other hand, mTORC1 hyperactivation and autophagy blockage have been associated with an increase in the formation of protein aggregates, this promoting the transference and expansion of neurodegenerative diseases. Then, the ability of Sambucus nigra flowers in the regulation of mTORC1 signaling activity and the reduction in oxidative stress through the activation of autophagy/mitophagy flux is also examined. In this regard, search for different molecules with a potential inhibitory effect on mTORC1 activation could have multiple positive effects either in the molecular pathogenic events and/or in the progression of several diseases including neurodegenerative ones.  相似文献   
10.
A newly discovered physical mechanism involving incoherent electron tunneling in layers of the protein ferritin that are found in catecholaminergic neurons (catecholaminergic neuron electron transport or CNET) is hypothesized to support communication between neurons. Recent tests further confirm that these ferritin layers can also perform a switching function (in addition to providing an electron tunneling mechanism) that could be associated with action selection in those neurons, consistent with earlier predictions based on CNET. While further testing would be needed to confirm the hypothesis that CNET allows groups of neurons to communicate and act as a switch for selecting one of the neurons in the group to assist in reaching action potential, this paper explains how that hypothesized behavior would be consistent with Integrated Information Theory (IIT), one of a number of consciousness theories (CTs). While the sheer number of CTs suggest that any one of them alone is not sufficient to explain consciousness, this paper demonstrates that CNET can provide a physical substrate and action selection mechanism that is consistent with IIT and which can also be applied to other CTs, such as to conform them into a single explanation of consciousness.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号