Retention data from reverse‐phase high‐performance thin‐layer chromatography in characterization of some bis‐salicylic acid derivatives

The chromatographic behaviour of salicylic acid derivatives was investigated using reversed‐phase high performance thin‐layer chromatography (RP HPTLC) with methanol–water and dioxane–water binary mixtures as mobile phase in order to establish relationships between chromatographic data and selected physico‐chemical parameters that are related to ADME (absorption, distribution, metabolism and elimination). Some of the investigated compounds were screened for antioxidant activity. Examination of chromatographic behaviour revealed a linear correlation between R_M values and the volume fraction of mobile phase modifier. Obtained R_M⁰ values were correlated with lipophilicity, solubility, human intestinal absorption, plasma‐protein binding, and blood–brain barrier data. The comparison among chromatographic data obtained by two mobile phase was performed with a statistical technique, principle component analysis. Copyright © 2009 John Wiley & Sons, Ltd.     

The study of the lipophilicity of some aminoalkanol derivatives with anticonvulsant activity

A series of new (phenoxyethyl)aminoalkanol derivatives were synthesized and evaluated for their anticonvulsant activity. The most promising compound seemed to be (R,S)‐1N‐[(2,6‐dimethyl)phenoxyethyl]amino‐2‐butanol, which displayed anti‐MES activity (in mice, i.p.) with protective index (TD₅₀/ED₅₀) of 5.712, corresponding to that of phenytoin (6.6), carbamazepine (4.9) and valproate (1.7). The lipophilicity of compounds 1–17 exhibiting anticonvulsant activity was investigated. Their lipophilicities (R_M0) were determined using reversed‐phase thin‐layer chromatography (RP‐TLC) with a mixture of acetone and water as mobile phases. The partition coefficients of 1–17 (logP) were also calculated using two computer programs (Pallas and ALOGPS) and compared with R_M0. The relationship between anticonvulsant activity and lipophilicity of the tested substances was estimated. Copyright © 2010 John Wiley & Sons, Ltd.     

Chromatographic Study of Novel Heteronuclear Complexes with Schiff Base as Main Ligand

The properties of 12 new heterodi- and heterotrinuclear complexes having general formulae [Cu₂Ln(L)₂(NO₃)(H₂O)₂](NO₃)₂·3H₂O [where Ln = Pr (1), Nd (2), Sm (3) and Eu (4)], and [CuLn(L)(NO₃)₂(H₂O)₃MeOH]NO₃·MeOH [where Ln = Gd (5), Tb (6), Dy (7), Ho (8), Ef (9), Tm (10), Yb (11) and Lu (12)], and their main ligand [L = C₁₉H₁₈N₂O₄Br₂ = N,N’-bis(5-bromo-3-methoxysalicylidene)propylene-1,3-diamine] have been characterized by chromatographic analyses. The parameter of relative lipophilicity (R _M0) of the tested compounds was determined experimentally by reversed-phase high-performance thin layer chromatography method with mixtures of methanol and water as a mobile phase. We also described interactions between chromatographed substances and various surfaces (silica—SiO₂ and modified by hydrocarbon chains—RP-2, RP-8, RP-18 phases). This study also investigates the effect of pH of the mobile phase on the retention on the polar stationary phase. Thin layer chromatography combined with magnetic and electric field has been proposed as a complementary method for the determination of physicochemical properties of the investigated compounds. The chromatograms in the field and outside of it were developed simultaneously in three identical chromatographic chambers. One of them was placed in external magnetic field of 0.4 T inductivity, and the second in external electrical field. In magnetic and electric fields, retention of some complexes changed, which indicated that the presence of these fields influenced physicochemical properties of the compounds and their interactions with the stationary phase.     

Quality assessment of Herba Leonuri based on the analysis of multiple components using normal‐ and reversed‐phase chromatographic methods

A novel, improved, and comprehensive method for quality evaluation and discrimination of Herba Leonuri has been developed and validated based on normal‐ and reversed‐phase chromatographic methods. To identify Herba Leonuri , normal‐ and reversed‐phase high‐performance thin‐layer chromatography fingerprints were obtained by comparing the colors and R _f values of the bands, and reversed‐phase high‐performance liquid chromatography fingerprints were obtained by using an Agilent Poroshell 120 SB‐C18 within 28 min. By similarity analysis and hierarchical clustering analysis, we show that there are similar chromatographic patterns in Herba Leonuri samples, but significant differences in counterfeits and variants. To quantify the bio‐active components of Herba Leonuri , reversed‐phase high‐performance liquid chromatography was performed to analyze syringate, leonurine, quercetin‐3‐O‐robiniaglycoside, hyperoside, rutin, isoquercitrin, wogonin, and genkwanin simultaneously by single standard to determine multi‐components method with rutin as internal standard. Meanwhile, normal‐phase high‐performance liquid chromatography was performed by using an Agilent ZORBAX HILIC Plus within 6 min to determine trigonelline and stachydrine using trigonelline as internal standard. Innovatively, among these compounds, bio‐active components of quercetin‐3‐O‐robiniaglycoside and trigonelline were first determined in Herba Leonuri . In general, the method integrating multi‐chromatographic analyses offered an efficient way for the standardization and identification of Herba Leonuri .     

Synthesis of betulin derivatives and the determination of their relative lipophilicities using reversed‐phase thin‐layer chromatography

A series of superlipophilic or highly lipophilic semisynthetic betulin derivatives was prepared and their relative lipophilicity was measured by reversed‐phase thin‐layer chromatography (RP‐TLC) at different pH values using 1,4‐dioxane–acetate buffer mixtures as mobile phases. Cholesterol, 17β‐estradiol and pure betulin were used as the reference compounds. Linear relationships were found between R_M values and 1,4‐dioxane concentrations in the mobile phases. LogP values were also calculated with computer programs ACD/LogP (ChemSketch 11.0, Advanced Chemistry Development Inc.) and ClogP (Daylight Chemical Information Systems Inc.). The empirical and theoretical data were compared, and the R_M0 values correlated well with logP. Two of the synthesized betulin derivatives are reported for the first time. Copyright © 2009 John Wiley & Sons, Ltd.     

Chromatographic descriptors in QSAR study of barbiturates

Barbiturate derivatives were evaluated for their parameters of biological activity by applying linear regression and two multivariate methods (Cluster analysis and Principal component analysis). The lipophilicity of the studied barbiturates was determined on the modified carriers C18 in mixtures of water and four organic modifiers separately (methanol, n-propanol, acetone and tetrahydrofuran) by performing reversed phase thin layer chromatography and by applying relevant software packages. Chromatographic and computational lipophilicity of the examined barbiturates was correlated with the selected pharmacokinetic and toxicological predictors and good relationships were obtained. More concrete results were obtained by multivariate methods which showed that the polarity of the substituent has the greatest influence, and its electronic effects to a lesser extent on the tested parameters of the barbiturate derivatives. Results obtained by multivariate methods also suggest that the chromatographic retention constant, R_M⁰, shows a greater resemblance to the parameters of lipophilicity. The chromatographic parameter m, exhibits better agreement with the toxicity parameters.     

Estimating the lipophilicity of a number of 2‐amino‐1‐cyclohexanol derivatives exhibiting anticonvulsant activity

The lipophilicity of a number of N‐acyl derivatives of trans‐ or cis‐: racemic, (1R,2R)‐ or (1S,2S)‐aminocyclohexanol (1–13) exhibiting anticonvulsant activity was investigated. Their lipophilicity (R_{m 0}) was determined using reversed‐phase thin‐layer chromatography (RP‐TLC) with mixtures of methanol and water as mobile phases. The partition coefficients of compounds 1–13 (log P) were also calculated using two computer programs (Pallas and Chem DU) and compared with R_{m 0}. Copyright © 2009 John Wiley & Sons, Ltd.     

A comparative study concerning chromatographic retention and computed partition coefficients of some precursors of peraza crown ethers

Retention indices for some precursors of peraza crown ethers were determined by reversed phase high-performance thin layer chromatography on RP-18 plates with methanol-water in different volume proportions as mobile phase. The Log P values for the same compounds were calculated using different computer programs: SciQSAR, SciLogP, Chem3D Ultra 8.0, XLOGP (based on atom contributions), Chemaxon and KOWWIN (based on atom/fragment contributions), cLogP (based on fragmental contributions), ALOGPS and IAlogP (based on atom-type electrotopological-state indices and neural network modeling). A comparative study concerning lipophilic parameters (R_M0, b and ϕ0) and computed partition coefficients has been developed. Taking into account the correlation coefficients between determined and calculated Log P values, it seems that R_M0 and b are less suitable than ϕ₀ for estimating lipophilicity of the compounds investigated, and cLogP and ALOGPS provide the best correlations with experimental values.     

The lipophilicity of parabens estimated on reverse phases chemically bonded and oil‐impregnated plates and calculated using different computation methods

The chromatographic behaviour of the parabens has been investigated on RP‐18F_254S, RP‐18WF_254S, CNF_254S, Diol F_254s and silica gel 60F₂₅₄ plates impregnated with different oils (paraffin, olive, sunflower and corn) using methanol–water mixtures in different volume proportions as mobile phases, the regression determination coefficients being excellent (higher than 0.98 for the majority of compounds). Moreover, highly significant correlations were obtained between different experimental indices of lipophilicity (R_M0, b and scores corresponding to the first principal component (PC1)) and computed log P values. All types of stationary phases investigated appear to be highly suited for estimating the lipophilicity of the parabens.     

Separation of betacyanins from flowers of Amaranthus cruentus L. in a polar solvent system by high‐speed counter‐current chromatography

Betacyanin extract of Amaranthus cruentus L. flowers was fractionated by semi‐preparative high‐speed counter‐current chromatography in a highly polar solvent system: propan‐1‐ol/acetonitrile/(NH₄)₂SO_{4satd. soln}/H₂O (1.0:0.5:1.2:1.0, v/v/v/v) in tail‐to‐head mode with 76% retention of the stationary phase. The crude extract as well as the fractions containing betacyanins were analyzed by liquid chromatography with tandem mass spectrometry as well as by high‐resolution ion‐trap time‐of‐flight mass spectrometry detection technique for the molecular formulae and multi‐step fragmentation pattern elucidation. Four betacyanins; namely, amaranthin, betanin, 6′‐O‐formyl‐amaranthin, and 6′‐O‐malonyl‐amaranthin as well as their diastereomeric forms differing in the configuration of the C‐15 carbon atom were identified in the fractions. Amaranthin was the dominant pigment in the extract and was additionally analyzed by nuclear magnetic resonance correlation techniques after the counter‐current chromatographic and high‐performance liquid chromatographic isolation. Betacyanins were highly enriched during a single high‐speed counter‐current chromatographic step; therefore, the tentative identification of new compounds for the whole Amaranthaceae family, 6′‐O‐formyl‐amaranthin and 6′‐O‐malonyl‐amaranthin was possible. Different elution profiles of the pigments observed in the counter‐current chromatographic system in comparison to high‐performance liquid chromatography system confirm a complementarity of both the techniques especially in the separation of diastereomeric pairs of betacyanins.     

Chromatographic and computational screening of anisotropic lipophilicity and pharmacokinetics of newly synthesized 1-aryl-3-ethyl-3-methylsuccinimides

The present study is focused on a series of newly synthesized 1-aryl-3-ethyl-3-methylsuccinimide derivatives, as potential anticonvulsants. The retention behavior of eleven succinimide derivatives was determined by using reversed phase high performance liquid chromatography (RP-HPLC) and reversed phase high performance thin layer chromatography (RP-HPTLC). The estimated retention behavior was correlated with partition (logP) and distribution coefficients (logD). These high correlations pointed out that the determined retention parameters (logk₀ and R_M⁰) can be considered chromatographic (anisotropic) lipophilicity of the studied succinimide derivatives. The structural properties, which dominantly affect the chromatographic lipophilicity, were determined as well. The significant correlations between the chromatographic lipophilicity and plasma protein binding (PPB), Madin-Darby Canine Kidney (MDCK) cells permeability, volume of distribution (Vd) and absorption constant (Ka) indicate the strong influence of lipophilicity on pharmacokinetics of 1-aryl-3-ethyl-3-methylsuccinimide derivatives. These derivatives have also been tested applying Comprehensive Medicinal Chemistry (CMC) drug-like rules which confirmed their drug-like properties. Besides, their blood-brain penetration (BBB) ability has been estimated applying the set of Clark’s rules and by using Pre-ADMET software. Regarding toxicity, it was predicted that only one compound from the set might have toxic effects by blocking the hERG potassium channel. The present study reveals which molecular features in the structure of novel succinimide derivatives could be crucial for their lipophilicity, and consequently for their pharmacokinetic properties. The results indicate that the newly synthesized series of succinimide derivatives should be further considered in design of novel anticonvulsants.     

Evaluation of N-Substituted 2,4-Dihydroxyphenylthioamide Fungicide Lipophilicity Using the Chromatographic Techniques HPLC and HPTLC

2,4-Dihydroxyphenylthioamide derivatives modified on the N-aryl ring have substantial fungicidal activity. To determine their quantitative structure–activity relationships their lipophilicity was determined by use of the chromatographic methods column liquid chromatography and thin-layer chromatography. Methanol–water systems were used as mobile phases and the linear dependences of retention (R_M and log k) on volume fraction of organic modifier, φ, were determined. This enabled precise determination of lipophilicity (R_Mw and log k_w) by extrapolation. Correlations were found between quantities characterizing the lipophilicity of the compounds. Deviations enabled discovery of compound structural features which increase or reduce lipophilicity. When these data were correlated with biological activity against the phytopathogenic fungi Alternaria alternata and Botrytis cinerea parabolic dependences were obtained.     

Drug–Membrane Interaction on Immobilized Liposome Chromatography Compared to Immobilized Artificial Membrane (IAM), Liposome/Water,and Octan‐1‐ol/Water Systems

The objective of this study was to investigate drug–membrane interaction by immobilized liposome chromatography (ILC; expressed as lipophilicity index log K_s) and the comparison with lipophilicity indices obtained by liposome/H₂O, octan‐1‐ol/H₂O, and immobilized artificial membrane (IAM) systems. A set of structurally diverse monofunctional compounds and drugs (nonsteroidal anti‐inflammatory drugs and β‐blockers) were selected in this study. This set of solutes consists of basic or acidic functionalities which are positively or negatively charged at physiological pH 7.4. No correlation was found between log K_s from ILC and lipophilicity indices from any of the other membrane model systems for the whole set of compounds. For structurally related compounds, significant correlations could be established between log K_s from ILC and lipophilicity indices from IAM chromatography and octan‐1‐ol/H₂O. However, ILC and liposome/H₂O systems only yield parallel partitioning information for structurally related large molecules. For hydrophilic compounds, the balance between electrostatic and hydrophobic interactions dominating drug partitioning is different in these two systems.     

Lipophilicity and bio‐mimetic properties determination of phytoestrogens using ultra‐high‐performance liquid chromatography

This paper presents lipophilicity and bio‐mimetic property determination of 15 phytoestrogens, namely biochanin A, daidzein, formononetin, genistein, genistein‐4,7‐dimethylether, prunetin, 3,4,7‐trihydroxyisoflavon, 4,6,7‐trihydroxyisoflavon, 4,6,7‐trimethoxyisoflavon, daidzin, genistin, ononin, sissotrin, coumestrol and coumestrol dimethylether. High‐performance liquid chromatography with fast gradient elution and Caco‐2 cell line were used to determine the physicochemical properties of selected phytoestrogens. Lipophilicity was determined on octadecyl‐sylane stationary phase using pH 2.0 and pH 7.4 buffers. Immobilized artificial membrane chromatography was used for prediction of interaction with biological membranes. Protein binding was measured on human serum albumin and α‐1‐acid‐glycoprotein (AGP) stationary phases. Caco‐2 assay was used as a gold standard for assessing in vitro permeability. The obtained results differentiate phytoestrogens according to their structure where aglycones show significantly higher lipophilicity, immobilized artificial membrane partitioning, AGP binding and Caco‐2 permeability compared with glucosides. However, human serum albumin binding was very high for all investigated compounds. Furthermore, a good correlation between experimentally obtained chromatographic parameters and in silico prediction was obtained for lipophilicity and human serum albumin binding, while the somewhat greater difference was obtained for AGP binding and Caco‐2 permeability.