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Chemistry and Chemical Engineering

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The retention behavior of twenty-four alkaloids has been investigated in normal-phase systems on thin layers of aminopropylsilica and bare silica developed with a variety of binary mobile phases prepared from n-hexane and polar modifiers – 2-propanol, ethyl acetate, methyl ethyl ketone, tetrahydrofuran, dioxane – in different concentrations. The retention factors obtained were fitted to the logarithmic Snyder–Soczewiński equation; the results are presented as the equation parameters and the statistical coefficients which prove the goodness of fit of the results with the displacement theory of retention.

The retention behavior of the alkaloids was also investigated in reversed-phase systems with buffered aqueous–acetonitrile mobile phases (pH 9.15) and the cyanopropyl- and octadecylsilica as stationary phases. Retention factors obtained for use of different concentrations of acetonitrile in the mobile phase were fitted to the semi-logarithmic equation or to quadratic polynomial equation selected for RP systems and are also presented as equation parameters and statistical coefficients which prove the goodness of fit of the results obtained with the theories derived for RP systems.

Separation selectivity was presented as the RF spectrum for the aminopropyl phase, comparing the separation selectivity obtained by use of different mobile phases, and as RF1 vs RF2 correlation diagrams for different systems, enabling selection of the most selective systems for separation of particular pairs or groups of alkaloids. Such correlation diagrams are presented for the aminopropyl phase and silica with four non-aqueous mobile phases and also for CN-silica and C18 phases, and for CN-silica and diol phases with aqueous mobile phases.

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The thin-layer chromatography of eighteen anions has been performed on silica layers with mixed aqueous–organic mobile phases. Binary mobile phases consisting of distilled water and acetone or acetonitrile were found suitable for resolving hexacyanoferrate(II) from hexacyanoferrate(III) or thiocyanate whereas ternary solvent systems consisting of distilled water, carbon tetrachloride, and acetonitrile was found most suitable for separating ternary mixtures of hexacyanoferrate(II), hexacyanoferrate(III), and thiocyanate. Distilled water–acetonitrile–carbon tetrachloride, 10 + 80 + 5, was the best mobile phase for separation of three-component mixtures of these anions in the presence of heavy metal cations and amino acids. The proposed method works well for the separation of Fe(CN)6 4–, Fe(CN)6 3–, and SCN from industrial waste water, saline water, hard water and fixer and bleach samples.

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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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