The effect of Ginkgo biloba (EGb 761) on epileptic activity in rabbits

Different animal models are used to evaluate the process of epileptogenesis. In this investigation the kindling model of epilepsy was used. The epileptic focus was induced in Chinchilla rabbits by stimulation of the hippocampus with electric stimuli. We presumed that the extracts of Ginkgo biloba affect the formation of kindling epilepsy. Bioelectric activity of the brain was registered throughout the development of kindling with and without standardized extracts from dried ginkgo leaves (EGb 761). For each animal the following has been determined: the values of the minimum current strength necessary for the origination of threshold after-discharge (AD) - discharges appearing after the cessation of stimulation; duration of the threshold AD; number of stimulations necessary for the origination of full kindling; time latency for the development of full kindling; number of spontaneous epileptogenic discharges manifested in EEG two days following the formation of full kindling during 60-minute registration. The results show that the process of epileptogenesis was influenced by EGb 761. It has been established that if the animals received EGb 761, significantly weaker minimum current strength was necessary for the development of the epileptogenic focus and the AD were longer, while the number of necessary electrostimulations for the appearance of full kindling was less and the latency was shorter.     

基于果糖自氧化体系的抗氧化剂筛选方法

机体内果糖的自氧化过程中会产生多种自由基, 并最终转化为羟自由基, 苯甲酸钠可捕获羟自由基生成具有强荧光信号的羟基苯甲酸钠. 本文采用荧光光度法考察了影响果糖自氧化体系的各种因素, 建立了果糖自氧化产生羟自由基体系. 实验结果表明, 在果糖浓度为8.00 mmol/L, CuSO₄浓度为20.0 μmol/L, 苯甲酸钠浓度为24.0 mmol/L, pH=7.4, 温度为37℃及反应时间为24 h的条件下, 果糖自氧化体系最终可产生19.27 μmol/L的羟自由基. 抗氧化剂的存在可清除果糖自氧化过程中产生的自由基, 使最终生成的羟自由基的量减少, 从而导致生成的羟基苯甲酸钠减少, 荧光信号减弱, 由此建立了基于果糖自氧化体系的抗氧化剂筛选方法. 利用本评价体系考察了抗氧化剂盐酸小檗碱和阿魏酸的抗氧化能力, 实验结果表明, 中药标准品盐酸小檗碱和阿魏酸均能有效清除果糖自氧化体系产生的羟自由基, 其IC₅₀值分别为0.023和0.036 mmol/L.     

Microchip Electrophoretic Analysis of Phaseolin Patterns and Its Comparison with Currently Used SDS-PAGE Techniques

The goal of this work was to compare reproducibility of phaseolin patterns of common bean obtained by two electrophoretic protein separation techniques including the conventional SDS-PAGE and an automated chip electrophoresis system. Five standard cultivars of common bean provided by the United States Department of Agriculture (Beltsville, Maryland) that represented five phaseolin types, T (Tendergreen), C (Contender) and S (Sanilac), B (Boyaca) and P (Pampa), were used in this study. Comparison of the phaseolin patterns revealed that the chip-on-a-lab electrophoresis provided a good reproducibility. The phaseolin polymorphism included four to seven polypeptides typical for the pattern composition of the T, C and S types. The polymorphism of the B and P patterns was also established. Phaseolin polypeptides separated by the microchip electrophoresis exhibited differences with respect to the molecular weights and electrophoretic mobility as compared to the SDS-PAGE technique. This phenomenon could be attributed to the absence of a solid separation phase in the microchip electrophoresis. Moreover, this technique has potential to substantially accelerate screening of large bean germplasm collections since it allows for the accurate analysis of the higher number of individual plants within accessions than the conventional, tedious and time consuming SDS-PAGE method.     

Off-Line and On-Line Preconcentration Techniques for the Determination of Phenylureas in Freshwaters

Abstract

Phenylurea herbicides are analysed by reversed-phase liquid chromatography using UV detection at 244 nm after a concentration step in order to determine ppb or sub-ppb levels in drinking and river waters. With an average UV detection limit of 5 ng, a 500 ml sample volume is necessary to reach the 10 ppt level for spiked LC grade water samples and enables easy determination of concentrations below the ppb level for river water samples. Off-line and on-line methods are compared for the concentration step. Off-line concentration consists in a liquid sorption on n-octadecyl silica (C18) and elution by a suitable organic solvent. Polar phenylureas have low retention volumes on C18 silica and consequently the length of the concentration column has to be 10 cm to concentrate them at the ppb level from 100 ml of water and longer for lower levels of detection. Nevertheless, we show that increasing the size of the concentration column does not improve the limits of detection because of the numerous interferences also concentrated when percolating high volumes of water. On-line technology can be used only with short precolumns and requires a sorbent with a great retention for phenylureas. The copolymer-based PRP-1 is found to be an excellent sorbent and it is then possible to apply on-line precolumn technology with preconcentration through two precolumns (10 × 21 mm ID) in series, the first one being packed with C18 silica and the other with the PRP-1 polymer. Interfering compounds are then trapped onto the first precolumn acting as a filter and common phenylurea-breakthrough volumes on the PRP-1 precolumn are higher than 500 ml. Knowing the amounts preconcentrated on both precolumns and using UV and electrochemical detection help the identification of phenylureas in river water.     

贻贝中多氯联苯分析的前处理方法研究

针对分析贻贝中痕量多氯联苯（PCBs），比较了索氏提取（SE）和加速溶剂萃取（ASE）两种提取方法，结果表明SE对贻贝中7种PCBs（PCB28、PCB52、PCB101、PCB118、PCB153、PCB138、PCB180）回收率范围在96％～125％，ASE回收率范围在102％～115％，两者提取效果相当，但与索氏提取相比，加速溶剂萃取是一种怏速、高效的提取方法此外采用凝胶渗透色谱（GPC）分别与Florisil和C18固相萃取（SPE）小柱联用净化，GPC与Florisil柱联用净化的凹收率范围在90％-112％，GPC与C18柱联用净化的回收率范围在74％-108％，结果表明GPC与Florisil柱联增净化优于GPC与C18柱联用净化。     

MIP—AAS测镍时2种放电—吸收管性能的比较

本文以镍为例,分别对MIP-AAS中所使用的T形和L形2种放电-吸收管的性能进行了详细的比较研究。讨论了各种实验参数对不同放电-吸收管的影响差异,从中总结出了一些初步的经验规律.     

Comparison of Two Novel Techniques for Eliminating Liquid Chromatography Gradient Ghost Peaks

Abstract

Distilled water to organic gradients in reversed phase liquid chromatography are often plagued with UV-detectable “ghost” peaks that can obscure sample peaks and complicate interpretation of results.^3,4 These contaminants usually come from the distilled water³ although it is possible for them to originate in the organic eluent⁴. The ghost-peak problem can be eliminated by using specially prepared “LC-grade” water, although this is expensive. In addition water can be cleaned with the Milli-Q ion-exchange system, containing a carbon absorption column⁵ but not where these systems contain buffers or organic amine eluting agents such as triethylamine phosphate. Gurkin and Ripphahn have shown that a C-8 silica column can be used off-line in a low- pressure mode to clean water⁶.     

Therapeutic Versus Preventative Use of Ginkgo biloba Extract (EGb 761) against Indomethacin-Induced Gastric Ulcer in Mice

The main bioactive constituents in the standardized Ginkgo biloba leaf extract (EGb 761) are the terpene lactones and flavonoid glycosides. EGb 761’s antioxidant and anti-inflammatory properties have previously been demonstrated. Indomethacin-induced gastric ulcers have a multifactorial etiology and represent a major restriction to its therapeutic utility. The underlying ulcerogenic process involves oxidative and inflammatory biomolecular insults. This study was performed to explore the curative and preventative benefits of EGb 761 in experimentally-induced ulcers. To develop gastric ulcers in mice, indomethacin (40 mg/kg) was administered orally. EGb 761 (200 mg/kg) was given by gavage for 7 days before (preventative) and after (therapeutic) indomethacin administration. The histological alterations and macroscopic mucosal lesions were assessed. In gastric tissue homogenates, malondialdehyde (MDA), reduced glutathione (GSH), nitric oxide (NO), and inflammatory cytokines were measured. The expressions of cyclooxygenase-2 (COX-2), cytokines, and proliferating cell nuclear antigen (PCNA) in the stomach mucosa were also investigated. The ulcer index, histological alterations, gastric oxidants, and inflammatory biomarkers were all significantly increased by indomethacin. In stomach specimens, it increased COX-2 and PCNA expression. EGb 761 treatments, both prophylactic and therapeutic, resulted in significant reductions in ulcer lesions, nitrosative and oxidative damage, and inflammatory markers, along with the lowering of COX-2 and PCNA expressions. Furthermore, in the fight against stomach ulcers, EGb 761 treatment was found to be more efficient than prevention.     

On-Line HPLC with Biochemical Detection for Screening Bioactive Compounds in Complex Matrixes

On-line high-performance liquid chromatography (HPLC) coupled with biochemical detection (BCD) has been developed to screen compounds showing antioxidant action, enzyme inhibition and receptor affinity in complex matrixes. This review summarizes HPLC methods combining different post-column detection methods, such as diode-array detection (DAD), mass spectrometry (MS), chemiluminescence (CL) and nuclear magnetic resonance, for antioxidant screening. The methods based on a single relatively stable reagent such as DPPH^• and ABTS^•+ were the most popular. Oxygen free radical scavengers mainly depended on post-column CL detection. The on-line hyphenated HPLC–BCD systems based on post-column UV/DAD fluorescence and MS detection were also widely applied to screen enzyme- and receptor-active compounds. These strategies provide a convenient tool for quick identification and quantification of active compounds in complex matrixes.

     

Comparison of Common Solvent Evaporation Techniques in Organic Analysis

Abstract

Isolation of organic constituents from water frequently involves an extraction with a large volume of organic solvent which must be reduced to achieve the desired sensitivity. The objective of this research was to evaluate common solvent evaporation techniques to determine which are acceptable for use in pollutant analysis. Techniques for solvent reduction from 200 to 10 mL (macro) and 8 to 0.2 mL (micro) were evaluated. The macro concentration technques included Kuderna-Danish (K-D) concentration, rotary evaporation, evaporation on a hot plate in an Erlen-meyer flask, and heated nitrogen blowdown in an Erlenmeyer flask. The micro techniques included micro K-D concentration, nitrogen blowdown, and nitrogen blowdown with a modified Snyder column. A series of model compounds covering a wide range of boiling points (108° to 323°C) and polarity was used. Based upon recovery efficiency alone, nitrogen blowdown was significantly superior to the other macro techniques; however, its extreme slowness gave K-D the highest Figure of Merit. With methylene chloride as the solvent, nitrogen blowdown with a column was the superior technique.     

Environmentally Friendly Techniques and Their Comparison in the Extraction of Natural Antioxidants from Green Tea,Rosemary, Clove,and Oregano

Many current food and health trends demand the use of more ecological, sustainable, and environmentally friendly techniques for the extraction of bioactive compounds, including antioxidants. However, extraction yields and final antioxidant activities vary between sources and are highly influenced by the given extraction method and nature and ratio of the employed solvent, especially for total polyphenols, flavonoids, and anthocyanins, which are well recognized as natural antioxidants with food applications. This review focused on the most common extraction techniques and potential antioxidant activity in the food industry for various natural antioxidant sources, such as green tea, rosemary, clove, and oregano. Green extraction techniques have been proven to be far more efficient, environmentally friendly, and economical. In general, these techniques include the use of microwaves, ultrasound, high hydrostatic pressure, pulsed electric fields, enzymes, and deep eutectic solvents, among others. These extraction methods are described here, including their advantages, disadvantages, and applications.     

Flow Injection and Related Techniques in Blood Studies for Clinical Screening and Analysis: A Review

Blood studies for clinical screening/analysis are geared toward point of care testing. Flow based techniques have expanded their applications with unique approaches that may be adaptable for use as alternative disease screening/diagnosis. Many newly developed systems for solution based chemical analysis can be easily adapted for use with plasma and serum. However, cell and intracellular analyses are different. Blood cell analyses require a particular way of sample introduction and detection. This review emphasizes the applications of flow based techniques, especially those that were coupled with FI/SI, in clinical studies through analysis of red blood cells and their intracellular substances.     

An Improved On-Line HPLC-DPPH Method for the Screening of Free Radical Scavenging Compounds in Water Extracts of Lamiaceae Plants

An on-line HPLC-1,1-diphenyl-2-picrylhydrazyl (DPPH*) method has been improved for the detection of polar and nonpolar radical scavenging compounds from complex plant extracts. Eight water extracts were prepared from steam-distilled essential oil-extracted Lamiaceae plants (Origanum vulgare L., O. Onites L., O. Minutiflorum O. Schwartz et P. H. Davis, O. Syriacum L., Satureja cuneifolia Ten., Thymbra spicata L., Coridothymus capitatus (L.) Reichb. f., Majorana hortensis Moench). After the components within each extract had been separated by reverse phase chromatography using 10% to 100% methanol with 2% acetic acid as a mobile phase, analytes capable of scavenging a citric acid-sodium citrate buffered methanolic DPPH* solution were detected by post-column derivatization at 517 nm. The HPLC-DPPH* on-line method was applied to the qualitative and quantitative analysis of these Lamiaceae plant extracts. There was a strong correlation between the scavenging (negative) peak area and the concentration of the radical scavenging reference substances used. The radical scavenging compounds within the extracts were determined as benzoic acid and hydroxycinnamic acid derivatives, flavonoids and diterpenoids according to their retention time and UV spectral data. Rosmarinic acid and carnosic acid were identified as the dominant radical scavengers in these extracts by this method.     

Comparison of Protein Precipitation,Turbulent Flow and Automated On-Line Solid Phase Extraction,as Plasma Sample Preparation Techniques for the Determination of Compound I by LC-MS-MS

Compound I is a novel subtype-selective 5-HT₁ receptor antagonist currently under pre-clinical investigation. A theoretical increase in sensitivity of about 4 times over the plasma protein precipitation method by the two on-line extraction systems tested should be expected due to the introduction of 100% of the analyte onto the column with both the on-line systems. The comparison of these three methods showed that the real gain in sensitivity was 4 times with Prospekt2? and 2 times with TurboFlow?. This might be explained by the different mobile phases used combined with different recoveries. Due to the improved chromatography, the higher sensitivity and lower carry-over observed for this compound, the Prospekt2? system was chosen in order to validate an analytical procedure for the quantitation of I in rat plasma followed by LC-MS-MS.     

基于微流控技术的蛋白质结晶及其筛选方法的研究进展简

微流控技术以其高通量、低消耗和集成化等优点成为蛋白质结晶微型化研究的重要手段. 本文综述了基于微流控技术的蛋白质结晶技术和方法,主要包括微泵微阀、液滴(Droplet)、滑动芯片(SlipChip)以及液滴实验室(DropLab)等技术. 此外,还针对当前膜蛋白在结构生物学研究中的重要地位,综述了应用于膜蛋白结晶的微流控技术的研究进展.     

On-Line Concentration Methods for Analysis of Fat-Soluble Vitamins by MEKC

A fast, selective and sensitive reversed phase liquid chromatographic method employing a C-18 column has been developed and validated for simultaneous analysis of four impurities of duloxetine hydrochloride, an antidepressant drug, viz., (S)-N,N-dimethyl-3-hydroxy-(2-thienyl)-propanamine, phenolic impurity, 1-napthol and duloxetine succinamide. Good separations were achieved by a gradient elution with mobile phase consisting of a mixture of phosphate buffer 14 mM containing 0.1% of sodium octanesulfonate, pH 3.0, at a flow rate of 0.8 mL min^?1. The detection was at 220 nm. The method was validated for precision, linearity and accuracy. Finally, the developed method was used to quantify the impurities during stability sample analysis of duloxetine hydrochloride drug products.     

Kinetics of Oxy-chemiluminescence and Its Use in the Analysis of Antioxidants

The influence of the antioxidant (chroman C₁, a synthetic analog of tocopherol) on the chemiluminescence kinetics during diphenylmethane and cumene oxidation is studied. Principles are considered for choosing a standard oxidized mixture in which the concentration and reactivity of an antioxidant are determined most reliably. The results of exact computer simulations and analytical calculations assuming quasi-stationarity with respect to different types of radicals are compared. A strategy is proposed to interpret the results and choose the experimental conditions (model oxidation system, type of hydrocarbon, interval of initiation rates) under which the antioxidant concentration and reactivity can be determined most reliably. The chemiluminescence method is used to study natural antioxidants in sunflower and corn oil.