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EN
Eight 17β-carboxamide glucocorticoids with local anti-inflammatory activity were selected and their retention behavior tested in six RP-HPLC systems (I–VI). logkw, a, and φ 0 parameters were calculated and correlation with previously determined logPo/w values was examined. RP-HPLC system IV, which consisted of cyano column and methanol–water mobile phases (50:50, 60:40, 70:30, and 80:20, v/v), was selected as the most reliable for lipophilicity prediction and used for the analysis of chromatographic behavior of remaining fourteen 17β-carboxamide glucocorticoids. Quantitative structure-retention relationships analysis was performed and PLS(logkw) model was selected as the most statistically significant. On the basis of selected model and interpretation of corresponding descriptors, new derivatives with higher logkw values and higher expected lipophilicity were designed.
2
Content available remote Ocena aktywności przeciwutleniającej i lipofilowości octanu eugenylu
PL
Przedstawiono badania aktywności przeciwutleniającej oraz lipofilowości octanu eugenylu (OE). Do identyfikacji OE zastosowano metody GC, FTIR/ATR, GC-MS oraz analizę widm 13C-NMR i 1H-NMR, a do oznaczeń aktywności antyoksydacyjnej wykorzystano metodę redukcji wolnego rodnika DPPH. W celu zbadania lipofilowości OE wyznaczono współczynnik podziału n-oktanol/woda (log P).
EN
Eugenol was esterified with AcOH in presence of (ClCO)₂ and pyridine (yield 100%, selectivity 100%). The ester was identified by mass IR and NMR spectroscopies and studied for antioxidant activity and lipophilicity. The antioxidant activity was detd. by the free 2,2-diphenyl-1-picrylhydrazyl radical redn. and increased from 25% up to 72% with in- creasing the ester concn. from 5 µg/mL up to 500 µg/mL. The octanol/water partition coeff. was a measure for the lipophilicity of the ester.
EN
The paper compares linear, quadratic, and cubical regression together with several weighted and robust approaches in the context of lipophilicity determination. The comparison is done on 35 model compounds on data from different modifiers used on RP18, CN, and silica plates. It can be concluded that the use of weighted and moderately robust regression technique increases correlation between extrapolated retention and real lipophilicity, whereas polynomial and very robust techniques give visibly worse results due to their excessive flexibility and higher extrapolation uncertainty. Additionally, we have compared averaging retention from different modifiers by RF, k, and RM values. The results are similar; however, surprisingly, RF averaging performs slightly better to the other approaches.
EN
In this study, the chromatographic behavior of a newly synthesized series of 1,4-disubstituted thiosemicarbazide derivatives and products of their dehydrocyclization is presented. These compounds have been subjected to this study because they exhibit antimicrobial activity. The compounds have been chromatographed on RP-18 and on cyano-bonded silica chromatographic phases with eluents containing water and an organic modifier (methanol, dioxane, acetone, acetonitrile or tetrahydrofuran) of various concentrations. Statistically proved linear relationships between the retention parameter (RM) and the concentration of organic modifier in the mobile phase allow the extrapolation procedure to obtain RM0 for investigated compounds. The correlations between both the values of the intercept (RM0 ) and the slope (S) from the linear equation, taken as a measure of the lipophilicity, were calculated. The experimentally established parameters of lipophilicity (RM0 ) were compared with the log P values calculated by use of four different software packages. The values of the correlation coefficients of these relationships are higher for the cyanopropyl phase than for RP-18. Moreover, in this work the influences of different mobile phase modifiers and adsorbent layers on experimentally obtained lipophilicity parameters were analyzed and compared. Generally, the best correlations were obtained for systems with the cyanopropyl-bonded stationary phase in comparison with RP-18.
EN
Some new derivatives of thiosemicarbazide and the 1,2,4-triazole of sulphanylacetic acid have been chromatographed on RP-18 HPTLC plates with mobile phases containing water and an organic modifier (methanol, dioxane, acetone, 2-propanol, or tetrahydrofuran). Relationships between solute retention and modifier concentration were described by Snyder’s linear equation. The equation was used to determine R M 0 values, by extrapolation, and the S values denoting the slopes of the relationship between linear retention and mobile phase concentration; both values characterize the lipophilicity of the substances. Calculated values of R M 0 were correlated with log P values for the drugs investigated by use of the software HyperChem. Correlations between intercept ( R M 0 ) and slope ( S ) from the linear equations were also calculated. The effects of different mobile phase modifiers on experimentally obtained lipophilicity were also analysed and compared.
EN
The relative lipophilicity, R M0 , and specific hydrophobic surface area of eleven 3-hydroxy-1,2-benzoisoxazoles substituted in the benzene ring (two isomeric fluoro, three isomeric chloro, three isomeric bromo and dibromo derivatives, and a nitro derivative) have been studied by reversed-phase thin layer chromatography (RP-TLC) on silica gel RP-C18 plates with methanol-water mixtures as mobile phases. Linear correlation between the volume fraction of methanol and R M values over a limited range was established with high correlation coefficients ( r > 0.99). Lipophilicity R M0 was compared with computed partition coefficients IAlogP, A logP s , clogP, milogP, logP KOWIN , and xlogP. The best correlation ( r > 0.9) was found between R M0 and logP KOWIN and xlogP values. Principal-components analysis (PCA) was also used to compare R M0 values with computed partition coefficients. The chromatographic behaviour of 3-hydroxy-1,2-benzisoxazoles was compared with that of their bioisosteric analogues 1,2-benzisot-iazolonoles. Experimental R M0 values for both groups of compounds were in accor-dance with the equation R M0 aR M0 +b(r> 0.9).
EN
The lipophilicity R M0 and log P TLC of thirteen novel, potentially biologically active, 12 H -quino[3,4- b] [1,4] benzothiazinium salts have been determined by reversed-phase thin-layer chromatography using RP-18 silica plates and methanol-aqueous Tris buffer solution mixtures as mobile phases. R M values of the compounds were linearly dependent on methanol concentration; extrapolation of these to 0% methanol gave the lipophilicity R M0 . log P TLC was obtained from R M0 by use of a calibration curve obtained for five standards of known experimental lipophilicity (log P). Lipophilicity log P calcd for the thirteen quinobenzothiazines was calculated by use of nine software products. The values determined were discussed in terms of structure-lipophilicity relationships. The results indicate that chromatographic lipophilicity R M0 can be used as a measure of the lipophilicity of the azaphenothiazine derivatives investigated.
EN
Lipophilicity indices for vitamins A and E, and for some precursors of vitamin A, have been determined for the first time by reversed-phase high-performance liquid chromatography (RPHPLC) on C 18 and C 8 columns. For each column the mobile phases were methanol-water mixtures with methanol in volume proportions from 86 to 90% ( υ/υ ) in 1% steps. The regression correlation coefficients obtained for both stationary phases were excellent (usually >0.999). To compare the experimental lipophilicity estimated for the compounds by use of log k′ w , S , φ 0 , the means of k′ and log k′ , and the scores of k′ and log k′ corresponding to the first principal component, and log P values calculated by use of different computer software a correlation matrix was constructed. Better correlations were obtained in both cases between the mean of k′ and the mean of log k′ , and scores corresponding to the first principal component obtained by applying principal-components analysis to the matrix of retention factors and computed log P values. The best correlations were found between the mean of k′ and scores corresponding to the first principal component determined on C 8 and most of the computed log P values.
EN
(Received April 9th, 2001; revised manuscript November 21st, 2001) An improved numerical procedure is presented in order to enhance the possibilities of fitting polynomial equations to predict log P data within the realm of the QSAR/QSPR theory. The use of real exponents instead of restricting to integer ones for the variables in the mathematical equations gives better results and a minor number of independent variables are needed to achieve a given accuracy degree. Some possible future extensions of the method are pointed out.
EN
In this review the current concepts of lipophilicity phenomenon are described. It especially deserves special attention in medicinal chemistry. Lipophilicity is the factor of crucial importance in biological action of chemical substances. It is the main physico-chemical determinant influencing the bioavailability, permeability and frequently the toxicity of drugs. Lipophilicity is thus one of the most important factors in research aimed at rational designing of new drugs, what is of great and still growing importance nowadays. In the present review the current definitions of lipophilicity and hydrophobicity are discussed. Next, the role of lipophilicity of drugs in living organisms is widely reviewed. The experimental methods of estimation of biological lipophilicity are described in their historical development. The most widely used method of measuring the lipophilicity of compounds is nowadays the liquid chromatography technique, especially in reversed phase mode (according to the definition of lipophilicity). RP-HPLC is a fast and very precise tool for determination of lipophilicity in a wide range of chemical compounds. In presented paper the influence of the chromatographic systems are described with special attention on novel stationary phases which closely mimic the biological environment (e.g., Immobilized Artificial Membrane phase). Next, the procedures for the determination of chromatographic lipophilicity parameters for a set of derivatives in polycratic and gradient modes are described. The importance of different retention parameters and their usefulness in assessing lipophilicity are widely examined. Finally, a brief description of calculating methods of lipophilicity estimations is presented.
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