Determination and Estimation of Aqueous Solubilities and n -Octanol/Water Partition Coefficients for Phenylacrylates
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Octanol
Objective To determine the solubility of cucurbitacin E and its partition coefficients for n-octanol-water and liposome-water solution systems. Methods The solubility, partition coefficient for n-octanol-water and liposome-water were measured by equilibrium method, shaking flask and equilibrium dialysis method, respectively. Results The solubility of cucurbitacin E in water was 0.155 mg•L^(-1), it was cosolvent in ethanol and tertiary butyl alcohol, the partition coefficients for n-octanol-water and liposome-water were (2.088±0.054) and (0.003-1.819), respectively. Conclusions Cucurbitacin E is insoluble in water, its partition coefficients for n-octanol-water and liposome-water are moderate.
Octanol
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Partition coefficients define how a solute is distributed between two immiscible phases at equilibrium. The experimental estimation of partition coefficients in a complex system can be an expensive, difficult, and time-consuming process. Here a computational strategy to predict the distributions of a set of solutes in two relevant phase equilibria is presented. The octanol/water and octanol/air partition coefficients are predicted for a group of polar solvents using density functional theory (DFT) calculations in combination with a solvation model based on density (SMD) and are in excellent agreement with experimental data. Thus, the use of quantum-chemical calculations to predict partition coefficients from free energies should be a valuable alternative for unknown solvents. The obtained results indicate that the SMD continuum model in conjunction with any of the three DFT functionals (B3LYP, M06-2X, and M11) agrees with the observed experimental values. The highest correlation to experimental data for the octanol/water partition coefficients was reached by the M11 functional; for the octanol/air partition coefficient, the M06-2X functional yielded the best performance. To the best of our knowledge, this is the first computational approach for the prediction of octanol/air partition coefficients by DFT calculations, which has remarkable accuracy and precision.
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Blind predictions of octanol/water partition coefficients at 298 K for 22 drug-like compounds were made for the SAMPL7 challenge. The octanol/water partition coefficients were predicted using solvation free energies computed using molecular dynamics simulations, wherein we considered the use of both pure and water-saturated 1-octanol to model the octanol-rich phase. Water and 1-octanol were modeled using TIP4P and TrAPPE-UA, respectively, which have been shown to well reproduce the experimental mutual solubility, and the solutes were modeled using GAFF. After the close of the SAMPL7 challenge, we additionally made predictions using TIP4P/2005 water. We found that the predictions were sensitive to the choice of water force field. However, the effect of water in the octanol-rich phase was found to be even more significant and non-negligible. The effect of inclusion of water was additionally sensitive to the chemical structure of the solute.
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The hydrophobicities of dissolved Al, Cu, Mn, and Pb have been determined in various contaminated natural water samples by 1-octanol extraction and C18 column retention. Octanol extraction varied among the metals studied and between the environments sampled but, in general, was greatest for Pb, whose conditional octanol−water partition coefficient, Dow, exceeded unit value in some samples. In most cases, metal partition into octanol either increased with increasing pH or exhibited a maximum under near-neutral conditions. Although the order and pH-dependence of metal retention by the C18 columns was consistent with these observations, the extent of retention was generally greater than the extent of metal extraction by octanol, possibly because of interferences effected by the C18 column matrix. Speciation calculations and results of controlled experiments employing metals in the presence of model ligands suggest that metals may become hydrophobic either by neutralizing relatively hydrophilic ligands or by combining with ligands that are intrinsically hydrophobic themselves. Given that octanol solubility affords an upper estimate of lipophilicity, the results of this investigation may have important implications regarding our understanding of metal bioavailability and toxicity in natural waters.
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A new apparatus is described for the measurement of the octanol–water partition coefficient, Kow; it incorporates features of the slow-stir, filter-probe and generator column methods. Drops of the aqueous phase are passed through a column of octanol solution and the approach to equilibrium is monitored by following the absorbance of the aqueous phase. Experiments were run with 13 acrylate esters; the group includes mono-, di-, tri- and tetra-acrylate esters and spans a large range of hydrophobicity. At equilibrium, the octanol phase was analysed for the ester and water, and the aqueous phase was analysed for the ester and octanol. For 12 compounds, the experiments were run at various concentrations and in all cases the concentration of ester in octanol is a non-linear function of the concentration of ester in water. The non-linearity can be explained by dimerisation of the ester in the octanol phase for 10 of the 12 compounds (group 1); the range of log Kow is −0.2 to 3.1. For two hydrophobic compounds (group 2), the non-linearity can be explained, in part, by tetramerisation of the ester in the octanol phase; the log Kow of these is 5.5 and 6.1. At the end of partitioning experiments, the molar absorption coefficients of group 1 correspond well with molar absorption coefficients of aqueous solutions that were prepared separately. In contrast, the molar absorption coefficients of group 2 are much higher than expected and are interpreted as measures of turbidence; this is evidence for the existence of micelles in the aqueous phase. Experiments with stearyl acrylate, the most hydrophobic ester of the thirteen, at a single concentration in the octanol phase show a strong dependence of the partition coefficient on the concentration of octanol in water. This may be interpreted by a micelle mechanism involving both octanol and the ester. Three esters form a series of the general structural form R1-(CH2CH2O)m-R2 with m=1, 2 and 3. The partition coefficient decreases with the increasing number of ethyleneoxy moieties, m; the inclusion of one moiety decreases log Kow by 0.1–0.2, in agreement with other work.
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Objective To determine the solubility of cucurbitacin E and its partition coefficients for n-octanol-water and liposome-water solution systems.Methods The solubility,partition coefficient for n-octanol-water and liposome-water were measured by equilibrium method,shaking flask and equilibrium dialysis method,respectively.Results The solubility of cucurbitacin E in water was 0.155 mg·L-1,it was cosolvent in ethanol and tertiary butyl alcohol,the partition coefficients for n-octanol-water and liposome-water were(2.088±0.054)and(0.003-1.819),respectively.Conclusions Cucurbitacin E is insoluble in water,its partition coefficients for n-octanol-water and liposome-water are moderate.
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The work covers synthesis and lipophilicity estimation of several BODIPY dyes. For these compounds, the distribution between 1-octanol and water layers is experimentally described and the corresponding partition coefficients LogP are calculated. The experimental LogP values are compared with popular fragment-based methods XLopP3, ALogPS, WLogP, SILICOS-IT and MLogP. Additionally, the hydrophobic and polar surface areas are found with quantum-mechanical calculations. That allowed to find a correlation between the LogP coefficient and the molecular surface topology, as well as to determine the corresponding incremental values of the methyl, acetyl, and phenyl substituents.
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Octanol
BODIPY
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Abstract The retention of eight non-congeneric amphoteric compounds was followed in a reversed phase (RP HPLC) system (C18/methanol-water vol. 50:50) in the pH range 4–9. The chromatographic behavior of the amphoterics is explained by means of their species distribution diagram (pH profile of the protonation macro- and microspecies) in the same pH interval. Maximum retention was observed at the isoelectric point of the compounds even in cases when the zwitterionic species was in a great excess over the neutral (uncharged) one. This finding reveals, that the retention at the isoelectric point (ie.p.) must be generated by the retention of the less polar, neutral form. The great similarity of pH dependent partition (octanol-water) and retention (C18/methanol-water) pattern provides further proof to the concept, that in case of amphoteric compounds the neutral species is transferred into the octanol phase during octanol/water partition. Linear correlation analysis showed that logPoct/w and Iogk'c18 are analogue lipophilicity parameters i.e.: the physico-chemical content of logk'c18 corresponds to that of the octanol/water true partition coefficient.
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Lipophilicity
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