Anna Hawrył

Application of normal- and reversed-phase 2D TLC on a cyanopropyl-bonded polar stationary phase for separation of phenolic compounds from the flowers of Sambucus nigra L.

Two-dimensional thin-layer chromatography on a cyanopropylbonded polar stationary phases has been used to separate phenolic compounds occurring in Flos Sambuci L. The separation was realized by development of the chromatographic plate in two directions with different mobile phases in each direction. Optimum systems were selected by analysis of retention data obtained for a variety of concentrations of polar solvents in a non-polar diluent (n-hexane) for NP TLC and polar solvents in water for RP TLC, both on thin layers of cyanopropyl-bonded polar adsorbents. The first development was performed by with a non-aqueous mobile phase and the second with an aqueous mobile phase. Eight flavonoids and three phenolic acids were separated by use of the method described.

Comparison of chromatographic properties of cyanopropyl-, diol- and aminopropyl- polar-bonded stationary phases by the retention of model compounds in normal-phase liquid chromatography systems.

Polar-bonded stationary phases, such as CN-, diol- and NH2-silica, have been characterised by the retention of model solutes (phenols, aromatic amines and quinoline bases) in normal-phase systems using n-heptane--polar modifier (2-propanol, tetrahydrofuran or dioxane) mixtures as eluents. The selectivity of separation for the particular groups of substances has been analysed by the log kI versus log kII relationships for CN- and diol, CN- and NH2- and NH2- and diol phases in examined eluent systems by the plotting of correlation lines. The values of regression coefficient r indicate either the similarity of the retention mechanisms of model solutes in some examined systems where r>0.9, or differences among various systems where r<<0.9. The values of slopes of correlation lines show the selectivity of separation for particular group of compounds. The selectivity of separation has also been characterised by deltalog k values. The effect of modifier (2-propanol, tetrahydrofuran and dioxane) on selectivity of model solutes on these phases has also been discussed.

Use of RP‐HPTLC Systems for the Determination of Lipophilicity of 3,5‐Dioxo‐4‐azatricyclo[5.2.2.02,6]undecanes–5‐HT1A Antagonists

Abstract The lipophilicities of twelve 3,5‐dioxo‐4‐azatricyclo[5.2.2.02,6]undecanes, potential serotonergic 5‐HT1A receptors antagonists, was determined by means of the reversed‐phase RP‐18W and RP‐18 thin‐layer chromatography. The use of the linear (Soczewinski‐Wachtmeister) and square (Schoenmaker) equation for R MW calculation was evaluated. Due to the rather poor correlation between linear and square R MW values, despite very good correlation coefficients for independent measurements for each solvent system, the results of the RP‐18 measurements and use of the linear equation for the R MW calculation were found to be the most reliable. Their reliability was also confirmed by the best values of F and s. The standardization (for six standards of known lipophilicity – log P) allowed calculation of the experimental lipophilicities (log P EXP ) for compounds investigated.

Chromatographic and Calculation Methods for Analysis of the Lipophilicity of Newly Synthesized Thiosemicarbazides and their Cyclic Analogues 1,2,4-Triazol-3-thiones

This paper describes the evaluation of the lipophilicity of newly synthesized thiosemicarbazides and their cyclic analogues 1,2,4-triazol-3-thiones obtained using experimental and calculated methods. Previous studies have shown these compounds have antibacterial activity. The chromatographic behavior of analyzed compounds was studied by reversed phase high performance liquid chromatography (RP-HPLC) and reversed phase thin layer chromatography (RP-TLC). The aqueous mobile phases containing methanol were used in order to determine retention parameter (RM) and capacity factors (log k) of analyzed compounds. The lipophilicity parameters were obtained by linear extrapolation and they were compared with the calculated log P obtained using several software packages. The results indicate that both experimental chromatographic methods yielded similar results, and these methods are appropriate for determining the lipophilicity of analyzed compounds. High values of correlation coefficients between the log P values calculated using known algorithms (milogP, ALOGPs, AClogP, AlogP, MLOGP, KOWWIN, XLOGP2, XLOGP3) and the experimental data were obtained. Eight standard solutes with known log POW were analyzed under the same conditions as the tested substances in order to determine the log PHPLC and log PTLCparameters. A good correlation was obtained between log kw (or RMW) and the slope. All tested compounds were in agreement with the rule of five claims by Lipinski. The calculated log P values were experimentally confirmed (log PHPLC and log PTLC).

Determination of the lipophilicity of some psychotropic drugs by RP-TLC

Psychotropic drugs have been chromatographed on RP-18-HPTLC plates with mobile phases containing water, an organic modifier (methanol, dioxane, acetone, acetonitrile or tetrahydrofuran), and ion-pair reagents or ammonia. RF was measured for different concentrations of organic modifier. Relationships between solute retention and modifier concentration were described by the Soczewinski-Wachtmeister and Schoenmaker equations. The equations were used to determine RMW by the extrapolation method. Calculated values of RMW or C were correlated with log P values for the drugs, estimated by use of software. Significant correlations between the intercept (RMW) and slope (S) of the linear equations were also calculated. Chromatographic systems for which the RMW values obtained were close to calculated log P values can be used for determination of the lipophilicity of basic drugs.

TLC Profiles of Selected Cirsium Species with Chemometrics in Construction of Their Fingerprints.

The dried aerial parts of 12 plants of Cirsium species were extracted with the Soxhlet apparatus using dichloromethane and methanol as solvents. Next, the extracts were separated by TLC methods to obtain the fingerprint chromatograms. The analysis was performed on silica gel or RP-18 layers as stationary phases using the following eluents: ethyl acetate/formic acid/acetic acid/water (12/1.5/1.5/4; v/v) for silica gel, and 5% (v/v) aqueous solution of formic acid/methanol (70/30; v/v) for the first development and the same system in the proportion of 50/50 (v/v) for the second development for RP-18. The double development was applied in the case of RP-18 plates. The analysis was performed for all Cirsium methanolic extracts and five selected standards (naringin, apigenin, rutin, caffeic acid and chlorogenic acid). The results were analyzed using chemometrics. The comparison of individual Cirsium species and the identification of unknown species were performed using the similarity indices (Pearsons correlation coefficient, determination coefficient and congruence coefficient), distance indices (Euclidean distance, Manhattan distance and Chebyshevs distance) and Multi-Scale Structural SIMilarity. Based on chemometric analysis, the first extract of the widely grown species is identified as Cirsium arvense and the second one as Cirsium rivulare.

Micro Two-Dimensional Thin-Layer Chromatography and Chemometric Analysis of Essential Oils from Selected Mentha Species and Its Application in Herbal Fingerprinting

Micro two-dimensional thin-layer chromatographic systems (micro-2D-TLCs) were optimized using some popular nonaqueous mobile phases on 5 cm × 5 cm silica plates. The optimal 2D TLC systems were chosen based on correlations of RF values vs. mobile phases concentrations performed for 1D separations. Finally plates were developed using the following mobile phases: in the first direction – ethyl acetate/toluene (5/95; v/v) and in the second direction – ethyl acetate/n-heptane (15/85; v/v). Eleven essential oils obtained by hydrodistillation in Deryng apparatus from various mint specimens were separated and then 2D thin-layer chromatograms were densitometrically scanned at the wavelength of 254 nm. Digital images (exported from densitometer software as ASCII files) were processed using ImageJ free software, and then some chemometric parameters were calculated (determination coefficient, congruence coefficient, Euclidean’s distance, Manhattan’s distance, Chebyshev’s distance) and additionally, principal component analysis (PCA) was performed to determine the goodness of matching for individual essential oils. The chemometric analysis allows one to identify individual essential oils and the examined plant materials.

Chemometric analysis based on high-performance liquid chromatographic data in the fingerprint construction of selected Achillea species

ABSTRACT Fourteen Achillea species were collected, extracted using Soxhlet apparatus with dichloromethane and methanol as solvents. The obtained methanolic extracts were analyzed using the reversed-phase high-performance liquid chromatography–diode array detector (RP-HPLC-DAD) with the Kinetex C18 column and the mobile phase consisting of methanol–water–0.1% formic acid mixture (gradient 5–85% (v/v)) at 30°C with the run time of 45 min and the detection wavelength 320 nm. Next, the chromatograms were preliminarily processed with smoothing, noise reduction, background subtraction, and alignment in the SpecAlign program (version 2.4.1) to construct the fingerprints of studied extracts. Selected standards (phenolic acids and flavonoids) were analyzed in the same chromatographic conditions and its presence in extracts was confirmed based on their spectra and the retention time values. The chemical similarity between the samples was evaluated using the Pearson correlation coefficient as similarity parameter, Euclidean distance index, the principal component analysis, and cluster analysis (CA). GRAPHICAL ABSTRACT

Determination of Lipophilicity of New Thiosemicarbazide and 1,2,4-triazole-3-thione Derivatives Using Reversed-Phase HPLC Method and Theoretical Calculations

The lipophilicity of new thiosemicarbazide and 1,2,4-triazole-3-thione derivatives was determined using the RP-HPLC method, with the application of a mobile phase comprising methanol and water or acetonitrile and water. The logkW parameters were obtained by the extrapolation method using linear and quadratic equations. The lipophilicity data obtained experimentally (logkW, ϕ0) were compared with the calculated lipophilicity indices (logPHyperChem, milogP, clogP, ALOGPs, AClogP, AlogP, MLOGP, KOWWIN, XLOGP2, XLOGP3, logPChS). The matrices of these relationships were subjected to PCA analysis.

Determination of Lipophilicity of Allyl Thiosemicarbazide, N1-Thiocarbamylamidrazone Derivatives, and their Cyclic Products by RP-HPLC, RP-TLC, and Theoretical Methods: Effects of Selected Compounds on the CNS of Mice

The allyl thiosemicarbazide, N1-thiocarbamylamidrazone derivatives, and the products of their cyclization: the 1,2,4-triazole, 1,3,4-thiadiazole, 1,2,4-triazole[3,4-b]1,3-thiazine, 1,2,4-triazole[3,2-b]1,3-thiazine, 1,3,4-thiadiazole[3,2-a]pyrimidine, 5,6-dihydrothiazolo[2,3-c][1,2,4]triazole, and benzoic acid derivatives have been analyzed by RP-HPLC and RP-TLC methods using the methanol-water mixtures as the mobile phase and the octadecyl stationary phase. The lipophilicity was expressed as the chromatographically derived descriptors: mean of k (mk), mean of logk (mlogk), logkW, S, and ϕ0, scores of k, logk, and RM corresponding to the first principal component. Additionally, the authors propose to introduce a descriptor (logkm) corresponding to the residual specific interactions. Chromatographic parameters of lipophilicity were compared with the partition coefficient (logP) calculated by various softwares (milogP, clogP, AlogPs, AClogP, AlogP, MlogP, KOWWIN, XlogP2, XlogP3). The matrices were created with logkW or RMW and logP and they have been the subject of PCA analysis. The effects of the selected compounds on the central nervous system (CNS) of mice were studied.