Solvent and structural effects on the UV absorption spectra of N-(substituted phenyl)-2-cyanoacetamides.

UV absorption spectra of N-(substituted phenyl)-2-cyanoacetamides have been recorded in the range 200-400 nm in the set of selected solvents. The solute-solvent interactions were analyzed on the basis of linear solvation energy relationships (LSER) concept proposed by Kamlet and Taft. The effects of substituents on the absorption spectra were interpreted by correlation of absorption frequencies with Hammett substituent constant, σ. It was found that substituents significantly change the extent of conjugation. Furthermore, the experimental findings were interpreted with the aid of ab initio B3LYP/6-311G(d,p) method. Electronic energies was calculated by the use of 6-311++G(3df,3pd) methods with standard polarized continuum model (PCM) for inclusion of the solvent effect.

Reversed- and normal-phase liquid chromatography in quantitative structure retention-property relationships of newly synthesized seco-androstene derivatives.

The rational preselection of drug candidates includes also correlation between physico-chemical properties (lipophilicity, as the key one) and pharmacokinetic properties, as well as pharmacodynamic activity. Lipophilicity can be determined alternatively by chromatographic methods. Chromatographic behavior of nineteen newly synthesized derivatives of 16-cyano-16,17-seco-5-androstene has been studied by reversed-phase and normal-phase thin-layer chromatography (RP- and NP-TLC). Commercial plates RP-C18-HPTLC and water-dioxane and water-acetonitrile, as well as Lux(®) silica gel plates and toluene-dioxane and toluene-acetonitrile mixtures with different volume fractions of the solvents were used. Retention constants RM(0) and C0 for each compound were determined and correlated with (i) theoretical log P values and (ii) pharmacokinetic predictors determined in silico. Significant linear relationship was found between RP TLC retention constants, RM(0), and computational logP values as well as between NP TLC retention constants, C0, and logP. Lipophilicity values for the analytes, determined by RP TLC and NP TLC, were also correlated with computer calculated absorption constants, affinity for plasma proteins, volume of distribution and logarithm of blood-brain permeation. Significant linear relationships were obtained. These relations were further improved by introducing other regressors, as molecular size descriptors (molecular mass and/or volume) and a molecular polarity descriptor (total polar surface area). Retention parameters, RM(0) and C0, are recommended for lipophilicity expression of analyzed compounds. In silico pharmacokinetic descriptors for the analytes can be expressed as function of the lipophilicity determined by chromatographic methods, the size and the polarity of the molecules expressed as molecular mass/volume and total polar surface area. The analyzed seco-androstene derivatives have adequate lipophilicity which should provide druglikeness and good pharmacokinetic profiles and they can be recommended for further studies in which their biological activity would be examined.

Multivariate analysis of chromatographic retention data and lipophilicity of phenylacetamide derivatives.

One of the most important physicochemical parameters of a molecule that determines its bioactivity is its lipophilicity. Cluster analysis (CA), principal component analysis (PCA), and sum of ranking differences (SRD) were used to compare the lipophilic parameters of twenty phenylacetamide derivatives, obtained experimentally as chromatographic retention data in the presence of different solvents and calculated by different mathematical methods. All the applied methods of multivariate analysis gave approximately similar grouping of the studied lipophilic parameters. In the attempt to group the investigated compounds in respect of their lipophilicity, the obtained results appeared to be dependent on the applied chemometric method. The CA and PCA, grouped the compounds on the basis of the nature of the substituents R1 and R2, indicating that they determine to a great extent the lipophilicity of the investigated molecules. Unlike them, the SRD method could not be used to group the studied compounds on the basis of their lipophilic character.

RP TLC data in correlation studies with in silico pharmacokinetic properties of benzimidazole and benztriazole derivatives.

Reversed-phase thin-layer chromatographic (RP TLC) retention constants for a newly designed series benzimidazole/benztriazole with expected biological activity were determined as parameters of their lipophilicity and this series was recognized as congeneric. Pharmacokinetic descriptors of the compounds investigated were calculated in silico with the use of the established drug design software. The bioactivity descriptors, which are assumed to predicted drug absorption, distribution, metabolism, elimination and toxicity (ADMETox) in humans, were correlated with retention constants and good statistical parameters were obtained. Multiple regression analysis which was introduced suggested that the absorption through different epithelial membranes (intestinal, blood-brain or erythrocyte membrane) and distribution process depend on retention constants (as measure of lipophilicty) and total polar surface area and molar weight/volume of the analyte. Finally, the compounds with halogen substituent (compounds A4/A7 and A5/A8 in Table 1), were suggested as the best drug candidates, because of their predicted proper pharmacokinetics and have been proposed for further biological tests.

Chromatographic retention parameters in correlation analysis with in silico biological descriptors of a novel series of N-phenyl-3-methyl succinimide derivatives.

Reversed-phase thin-layer chromatographic (RP TLC) retention coefficients for a newly designed series of N-phenyl-3-methyl succinimide derivatives, of a rationally expected anticonvusant activity, were determined as parameters of their lipophilicity. Basic pharmacokinetic descriptors of the agents were calculated in silico with the use of the established medicinal chemistry/drug design software. Highly significant, predictive relationships were found between the chromatographic retention constants and the bioactivity descriptors, which are assumed to account for drug absorption, distribution, elimination and toxicity (ADMETox) in humans. Among the agents investigated, the compounds with halogen substituent (Compounds nos. 9-13 in Fig. 1), were identified as the best drug candidates, because of their predicted proper pharmacokinetics, and have been selected for further research and development studies on new antiepileptic drugs. At the same time, among the congeners studied these can be indicated, which should not be rationally subjected to bioactivity tests.

Reversed-phase TLC and HPLC retention data in correlation studies with in silico molecular descriptors and druglikeness properties of newly synthesized anticonvulsant succinimide derivatives.

The properties relevant to pharmacokinetics of two series of newly synthesized succinimide derivatives have been studied. The properties under consideration have been either determined empirically, by reversed-phase liquid chromatography (TLC and HPLC technique), or calculated with the use of established theoretical medicinal chemistry/drug design software. Chromatographic techniques allowed determination of the retention constants R(M)° and log k(w), which characterize lipophilicity of compounds. Considering potential pharmaceutical importance of succinimide derivatives, we (i) examined the retention behavior in the reversed-phase liquid chromatographic (RP LC) systems, in both planar and column LC, and (ii) determined the relationships between chromatographic data and selected structural features of analytes that are believed to markedly affect their processes of absorption, distribution, metabolism, excretion and toxicity (ADMETox). Significant relationships were found between the retention constants, R(M)° and log k(w), and the in silico calculated bioactivity descriptors, in particular HIA (human intestinal absorption) and PPB (plasma protein binding) parameters. The R(M)° and log k(w) values of the investigated compounds have been recommended for description of their lipophilicity and evaluating pharmacokinetic properties. In view of results of this study the newly synthesized succinimide agents meet pharmacokinetic criteria of preselection of drug candidates and hence qualify for pharmacodynamic phase of antiepileptic drug development. Best compromising human intestinal absorption and plasma protein binding features appear to be compounds A4, A5, A10 and A11.

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(M)(0) 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.

HPTLC chromatography of androstene derivates. Application of normal phase thin-layer chromatographic retention data in QSAR studies.

The chromatographic behavior of seven 16-oximino derivatives of 3beta-hydropxy-5-androstene have been investigated using the normal-phase (NP) HPTLC chromatographic mode of the type silica-non-polar diluent (benzene)-polar modifier (acetonitrile, ethyl acetate, or dioxane). The linear relationship between the retention constants (R(M)) and the logarithm of the organic modifier content in the mobile phase allowed for the calculation of R(M)0 values. The influence of substituent in the molecule on extrapolated retention data is discussed. To better understand the retention mechanism in the separation of androstene compounds, the functional group contributions (tauX) were compared with Hansch substituent constants (pi). An attempt to quantitate the lipophilicity of the investigated compounds using normal phase thin-layer chromatographic R(M)0 value was made. Also, the relative lipophilicity values determined previously by RPC as well as activity were compared with NPC data.

Evaluation of lipophilicity of some benzimidazole and benztriazole derivatives by RP HPTLC and PCA.

The lipophilic character of some benzimidazole and benztriazole derivatives was studied. The classical R(Mo) values were compared with the factors scores obtained by principal component analysis (PCA) based also onto the TLC retention data. The very high correlation between the R(Mo) values and slopes (specific hydrophobic surface area) indicated as usually that this group of compounds could be considered as a homologous series independently of their structural heterogeneity. It is emphasized once again that this procedure can not be a rational and objective way for congeneric studies because always there is a high correlation between slope and intercept. The reliability of the factor scores values as lipophilic indices are shown by their high correlation with the classical R(Mo) values. In addition, the 'lipophilicity chart' described by the first two components has the effect of separating compounds from each other most effectively from the congeneric aspect point of view. The most lipophilic compounds appeared to be the benzimidazole derivatives.