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Combined technology for the synthesis, separation, screening, and analysis of combinatorial libraries is described. The technique enables a rapid route from synthesis to the testing of chemical compounds. Chemistry can be rapidly optimized and vital information obtained by testing by-products and reagents simultaneously if desired. Screening can be performed without need for reaction work-up and without the need for undesired chemical manipulation, or further handling. Emphasis has been given to bioautographical/agar overlay screening methods for the testing of antimicrobial agents.

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Abstract

There has been a lively interest on macrocyclic polyamine alkaloids due to their remarkable pharmacological activities such as anti-tumor, anti-inflammatory, anti-Alzheimer's disease and anti-parasitic. Tripterygium wilfordii is a widely used traditional Chinese medicine, which is abundant in alkaloids including macrocyclic polyamine alkaloids. However, there are rarely studies on macrocyclic spermidine alkaloids of T. wilfordii so far. In this article, we use three known macrocyclic spermidine alkaloids celafurine, celabenzine and celacinnine, and successfully develop a simple and sensitive HPLC method for simultaneous quantification of macrocyclic spermidine alkaloids in root, stem and leaf of T. wilfordii.

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Abstract

β-sitosterol (BS) and lupeol (LU) exhibit a number of biological activities and are the important bioactive marker compounds in pharmaceutical science. In the present study, a simple, precise, accurate and validated high performance thin layer chromatographic (HPTLC) method was developed for simultaneous quantification of these two compounds in leaves, stem and roots of Uraria picta, a critically endangered medicinal plant and one of the important constituents of ten plants ayurvedic formulation called Dashmoola. Standards and test samples were applied on TLC aluminum plate precoated with 0.2 mm layer of silica gel 60F254. The plate was run in a twin glass chamber comprising toluene: methanol: chloroform (8:1:1, v/v/v) as a mobile phase. The plates were immersed in anisaldehyde-sulfuric reagent and then heated at 105 °C for 5 min in CAMAG TLC plate heater for appearance of bands. Densitometric scanning was performed at λ max = 525 nm using tungsten light source in CAMAG TLC Scanner4 armed with WinCATS software. R F values of BS and LU standards and those of test samples were found to be 0.53 ± 0.01 and 0.63 ± 0.01 respectively. The method was further validated by following the International Conference of Harmonization (ICH) guidelines. For BS and LU, the linear regression data for the calibration plots revealed a satisfactory linear association with r 2 = 0.995 and 0.998, respectively. Linear range for both BS and LU was 200–600 ng/band. Accuracy of the method was evaluated by performing recovery study at three different levels by standard addition methods with an average recovery of 99.86% and 101.07%. The results revealed that the leaf samples of U. picta contained highest concentration of BS (0.150 ± 0.02%) while its root samples confined the highest concentration of LU (0.149 ± 0.01%). The developed method can be applied for routine and quality control analysis in different herbal formulations containing U. picta species.

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A new simple, precise, rapid, and selective high–performance thin-layer chromatography (HPTLC) method has been developed for the analysis of finasteride in pharmaceutical formulations. The method uses loratadine as an internal standard. The stationary phase was silica gel 60F254 prewashed with methanol; chloroform–ethyl acetate, 6 + 4 (v/v) was used as mobile phase. Detection and quantification were performed densitometrically at λ = 228 nm. The linear range of the analysis was 0.2–2.0 μg and the percentage recovery was 101.8%.

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A high-performance thin-layer chromatographic method with densitometric detection has been used to determine the convallatoxine content of extracts from the various parts (flowers, leaves, and underground parts such as the rhizomes and buds on the rhizomes) of the plant. Plant extracts were separated on thin layers of silica gel Si 60F254 by multiple gradient development. The convallatoxine content was determined by densitometry and the results were evaluated statistically.

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This review covers the use of topological indexes based on the adjacency and distance matrixes to predict the R F and R M values, and the physicochemical properties, of a variety of groups of organic compounds investigated by TLC. This review indicates that further investigations on the application of the topological indexes in TLC are justifiable.

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The solvation parameter model has been used to characterize the retention properties of a varied group of solutes in silica gel thin-layer chromatography (TLC) and in silica gel and alumina column liquid chromatography. The model was unable to describe retention on silica gel TLC plates with the R M value as the dependent variable for five single-solvent mobile phases. The results were improved by fitting the retention data to the simple competition model and separating the solute and solvent contributions (denoted S and eºA S, respectively) to the free energy of adsorption on the inorganic oxide. Separate models were then constructed to enable estimation of values of S and A S from structure. These models were successful in describing retention in column liquid chromatography on silica gel with mixtures of methyl t-butyl ether and hexane as a mobile phase. This approach proved less reliable for calculating retention in TLC, probably because of non-equilibrium in the separation system. Evidence is presented that neither the solute adsorption parameter (S) nor the solute cross-section (A S) as used in these studies is unambiguously defined. Further refinements aimed at establishing clearly defined solute and solvent adsorption terms, and possibly including selective solute–solvent interactions in the mobile phase as a secondary contribution to retention, could result in improved model performance. The approach described here should be considered preliminary and thought of as a stepping stone in the direction towards a comprehensive model for structure-driven method development in normal-phase separations, which are currently less developed than models available for reversed-phase separations.

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Persilben (3,5-methoxy-2-hydroxy-E-stilbene) was satisfactorily separated on thin layers of silica gel, by use of two-step gradient elution, and quantified by densitometric techniques. The results were evaluated statistically. Eight acetone extracts from herbs and rhizomes of six taxons of Polygonum L. genus: P. lapathifolium ssp nodosum (Pers.) Dans., P. lapathifolium ssp. tomentosum (Schrank) Dans., P. hydropiper L., P. bistorta L., P. amphibium L., P. convolvulus L. (Bilderdykia convolvulus L.) were studied. Persilben was detected in the herbs of five taxons of Polygonum L. The amounts of the compound ranged between 46.3 and 174.2 μg g 1 dry herbs.

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A new horizontal sandwich chamberis described in this paper. Mobile phase can be applied to any part of the plate by use of this chamber. This has enabled a new mode of development in TLC, in which the starting position of development can be anywhere instead of at the origin; we therefore call this new mode ‘half-way development’. Compared with traditional development, the new mode can be used to develop any separated spot again. Many other modes of development can also be performed with this chamber, for example relay development on an over-length plate, programmed multiple development, gradient development, band application, concentration, and micropreparative separation. These methods are simple and convenient and give good results.

Mixtures of dyes have been used to verify above supposition with the above-mentioned methods. The results obtained are satisfactory.

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