Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Octanols”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8Linked to original sources
PubMed1998

The effect of ionic strength on liposome-buffer and 1-octanol-buffer distribution coefficients.

The distribution of salmeterol and proxicromil between unilamellar vesicles of dioleoylphosphatidylcholine (DOPC) and aqueous buffer at pH 7.4 has been studied, using an ultrafiltration method, as a function of compound concentration, DOPC concentration, and buffer ionic strength. The binding of these ionized lipophilic compounds to neutral DOPC vesicles induces a surface charge, which causes the observed membrane distribution coefficient D(mem)obs to vary significantly with bound compound to DOPC ratio and with ionic strength. This variability is shown to be well-described with use of the Gouy-Chapman theory of the ionic double layer and is contrasted with the ideal behavior shown by the neutral compound clofibrate. Increasing ionic strength is also shown to increase the observed 1-octanol-buffer distribution coefficients D(o/w)obs of proxicromil but through a very different mechanism involving the extraction of ion pairs. This study highlights the experimental difficulty in determining concentration-independent liposome distribution coefficients of ionized lipophilic compounds and describes when deviations will be significant and how observed values may be corrected for such effects. The general effect of ionic strength on membrane-buffer distribution and 1-octanol-buffer distribution is discussed with particular reference to the very different propensity for ion pair formation shown by the two systems, and the most suitable experimental conditions that should be used with each system.

1-Butanol↗
PubMed2003

Evaluation of a reversed-phase column (supelcosil LC-ABZ) under isocratic and gradient elution conditions for estimating octanol-water partition coefficients.

The solvation parameter model is used to identify suitable chromatographic models for estimating the octanol-water partition coefficient for neutral compounds of varied structure by reversed-phase liquid chromatography. The stationary phase Supelcosil LC-ABZ with methanol-water mobile phases affords a series of suitable correlation models for estimating the octanol-water partition coefficient (log KOW) under isocratic and gradient elution conditions. Isocratic separations with mobile phase compositions containing from about 25 to 40% (v/v) methanol provide the most accurate results for log KOW values in the range -0.1 to 4.0. Gradient separations programmed from 5 to 100% (v/v) methanol are suitable for faster separations of compounds with large log KOW values. The standard error in the estimate for the regression models of the predicted log KOW values against literature values are 0.135 log units for the 30% (v/v) methanol-water isocratic system and 0.263 log units for the methanol-water gradient system. Isocratic retention factors predicted from two gradient separations with gradient times of 15 and 45 min afford a poorer fit for the correlation models between log KOW and the estimated retention factors than that of either the above isocratic and gradient models. Plots of the retention factor (log k) as a function of mobile phase composition are generally non-linear. Values of log kw obtained by non-linear extrapolation to a volume fraction of 0% (v/v) methanol do not afford a useful model for estimating log KOW.

Journal Article↗
PubMed1993

Evaluation of potential strontium chelators in an octanol-water system.

90Sr has a physical half-life of sufficient duration to make it a potentially dangerous contaminant from nuclear accidents and radioactive wastes. In the present study, the efficacy of 16 compounds as potential chelators of strontium was tested in vitro. Strontium solubilization from strontium carbonate and its distribution in an octanol-water system (Do/w) was determined in the absence and presence of alpha-ketoglutaric acid, Kryptofix 222, ethylenglycol-bis-(beta-amino-ethylether)-N,N-tetraacetic acid, diethylentriamine pentaacetic acid, Kryptofix 5, disodium chlodronate, disodium ethidronate, oxaloacetic acid, fumaric acid, D-gluconic acid, succinic acid, citric acid, D,L-2,3-diaminopropionic acid, 1,1-cyclohexanediacetic acid, tartaric acid, and trans-1,2-cy-clohexanediol. Kryptofix 222 and Kryptofix 5 significantly increased solubilized strontium, suggesting strontium chelation potential. Since in previous in vivo studies both compounds were also effective in the removal of strontium following internal contamination, it is concluded that the octanol-water system may be useful screening compounds with strontium chelation potential.

Bridged Bicyclo Compounds↗
PubMed2000

Heat capacity behavior in the critical region of the ionic binary mixture ethylammonium nitrate-n-octanol

At temperatures between 30 degrees C and 58 degrees C we have recorded the heat capacity of the ionic ethylammonium nitrate-n-octanol mixture of critical composition and also of the constituents. Different samples of the binary mixture have been measured with its upper critical demixing temperature T(c) varying between 41.04 degrees C and 46.87 degrees C, depending on small traces of water within the liquid under test. Almost identical heat capacity profiles result if the data are displayed as a function of the temperature distance to the actual T(c) value. In the homogeneous phase the critical contribution exhibits power-law behavior with the critical exponent alpha=0.11 as theoretically predicted for nonionic liquids and in conformity with our understanding of the ionic criticality as being asymptotically Ising like. The noncritical background part of the heat capacity can be related to the heat capacities of the constituents using a simple mixture relation. In the two-phase regime a series of almost perfectly reproducible events is found which may be taken to indicate the existence of nonequilibrium intermediate states in the ethylammonium nitrate-n-octanol system.

Journal Article↗
PubMed1997

Micellar electrokinetic capillary chromatography as a method for determination of n-octanol/water partition coefficients of pesticides.

Micellar electrokinetic capillary chromatography (MEKC) was used to determine the n-octanol/water partition coefficient (Kow) of nonionic and ionic organic chemicals, mainly herbicides. Three electrolyte buffer systems with different organic modifiers were tested to evaluate their effect on the linear relationship between log Kow and log k'. The effect of the pH value of injected samples on linear log Kow/log k' relationship of ionic chemicals was also evaluated. Since a good correlation was found between log Kow values and the logarithms of the capacity factor (k') of each tested organic solvent, other parameters were considered to evaluate the efficacy of the method, such as the rate of electroosmotic flow, the efficiency and reproducibility of the separation, and the separation number (n). The method was found to be applicable over a range of log Kow values from 0.72 to 5.1 and demonstrated a good predictive capability giving similar results to direct experimental measures, at least within classes of compounds with similar physico-chemical properties.

1-Octanol↗
PubMed1996

Estimation of octanol-water partition coefficients from a molecular similarity parameter.

For 1966 compounds for which experimental values of the octanol-water partition coefficient (as logKow) were known, the value of an intermolecular similarity parameter, S, was computed for all 3,863,190 possible pairs. The S parameter differs from those most often used to predict molecular properties in that S depends on the difference between whole structures rather than on the difference between two numbers derived from the structures individually. For each compound, the largest S values were used to estimate logKow, and the statistical quality of the results was compared with results for the same 1966 compounds obtained by fragment-constant methods.

1-Octanol↗
PubMed1983

Relationship between molar refraction and n-octanol/water partition coefficient.

The n-octanol/water partition coefficient (Pow) for organic chemicals which do not form the hydrogen bond was considered on the basis of London's dispersion force, because the dispersion force is the main component of van der Waals-type attractive forces between solute and solvent molecules. The dispersion force is a function of both the ionization potential and the molar refraction. As the variation of the ionization potential is small in comparison with that of the molar refraction, the latter is the most important factor to determine the value of Pow. Thus the relationship between Pow and the molar refraction can be established. The relationship was confirmed for some halogenated alkanes, alkenes and aromatics, and polycyclic aromatic hydrocarbons by analysis of observed values of Pow and calculated values of the molar refraction. Estimation of Pow from the molar refraction is advantageous for the preliminary hazard assessment of new chemicals, because direct measurement of Pow is laborious and time consuming for lack of information about analytical methods.

1-Octanol↗
PubMed1995

Rapid determination of logarithmic partition coefficients between n-octanol and water using micellar electrokinetic capillary chromatography.

Micellar electrokinetic capillary chromatography (MECC) was evaluated as a rapid screening tool for the determination of logarithmic partition coefficients between n-octanol-water (log P(OW)). The technique is performed by electrochromatographing a mixture of standards of known log P(OW). The logarithmic capacity factor of each standard was plotted against its log P(OW) to form a linear calibration curve for a given set of chromatographic conditions. The log P(OW) of an unknown is calculated by using its chromatographically determined capacity factor and extracting the log P(OW) value from the calibration curve. The method was evaluated with a set of model compounds with known log P(OW). The accuracy of the method was examined and found to be within the limits required for screening purposes. The correlation of log P(OW) values determined using HPLC and MECC for some novel compounds was examined. This technique allows the screening of log P(OW) at a rate of four samples per hour with minimal sample requirements (< microgram) and with extremely small solvent waste generated.

1-Octanol↗
PubMed1997

Partition coefficients (n-octanol/water) of N-butyl-p-aminobenzoate and other local anesthetics measured by reversed-phase high-performance liquid chromatography.

For the determination of the logarithmic partition coefficients between n-octanol and water (log P(o/w)) of local anesthetics, the pH of the aqueous phase needs to be adjusted to high values to ensure that the local anesthetics are in the unionized form. Using the shake-flask or the stir-flask method, this high pH may catalyze hydrolysis, leading to increasing amounts of impurities in time. These impurities exclude non-selective quantification methods like UV spectrometry and require repetitive quantitative analysis of both liquid phases resulting in a tedious and time-consuming method. A rapid reversed-phase HPLC method was developed to measure log P(o/w) of the local anesthetics N-butyl-p-aminobenzoate, methyl-p-aminobenzoate, benzocaine, procaine, mepivacaine, prilocaine, lidocaine, bupivacaine, etidocaine, tetracaine and oxubuprocaine.

1-Octanol↗
PubMedDate not supplied

Assessment of n-octanol/water partition coefficient: when is the assessment reliable?

A model, VLOGP, has been developed for assessment of n-octanol/water partition coefficient, log P, of chemicals from their structures. Unlike group contribution methods, VLOGP is based on linear free energy relationship (LFER) approach and employs information-rich electrotopological structure quantifiers derived solely from molecular topology. VLOGP, a robust and cross-validated model derived from accurately measured experimental log P values of 6675 diverse chemicals, has a coefficient of determination, R2, of 0.986 and a standard error of estimate of 0.20. When applied to the training set, the largest deviation observed between experimental and calculated log P was 0.42. VLOGP is different from other log P predictors in that its application domain, called Optimum Prediction Space (OPS), has been quantitatively defined, i.e., structures to which the model should not be applied for predicting log P can be identified. A computer-assisted implementation of this model within HDi's toxicity assessment software package, TOPKAT 3.0, automatically checks whether the submitted structure is inside the OPS or not. VLOGP was applied to a set of 113 chemicals not included in the training set. It was observed that for the structures inside the OPS the average deviation between experimental and model-calculated log P values is 0.27, whereas the corresponding deviation for structures outside the OPS is 1.35. This demonstrates the necessity of identifying the structures to which a model is not applicable before accepting a model-based predicted log P value. For a set of 47 nucleosides, the performance of VLOGP was compared with that of four published log P predictors; a standard deviation of 0.33 was obtained with VLOGP, whereas the standard deviation from other log P predictors ranged between 0.46 and 1.20.

1-Octanol↗
PubMed1983

Oscillations in some linear free energy relationships derived from partition coefficients of phenols between octanol and water.

In the partition of some resorcinol alkyl ethers between water and 1-octanol, the values of delta Gtrs do not increase in a regular way. Odd and even chain alkyl compounds show different, regular increases in delta Gtrs for addition of each methylene group. The unrecognized occurrence of this phenomenon in earlier data is pointed out, and its possible significance in medicinal chemistry is discussed.

1-Octanol↗
PubMed1990

Thermodynamics and mathematical modeling of the partitioning of chlorpromazine between n-octanol and aqueous buffer.

The distribution of chlorpromazine (CPZ) between aqueous buffer solutions and 1-octanol was studied over a wide range of pH, buffer concentration, and temperature. A mathematical model was developed to simulate the distribution profiles. It is assumed that only monomers of CPZ exist in the organic phase, whereas in the aqueous phase, association equilibria were assumed to occur. The model predicted the formation of dimers and no higher aggregates over most of the concentration range covered in this study. Thermodynamic parameters for the partition equilibria were evaluated from the equilibrium partition coefficients measured as a function of temperature. Positive values of delta H and delta S were obtained for the transfer of CPZ from the aqueous to the organic phase. The process is entropy controlled indicative of a hydrophobic interaction between CPZ and the aqueous solvent.

1-Octanol↗
PubMed1987

Correlation between n-octanol/water partition coefficient and liquid chromatographic retention for caffeine and its metabolites, and some structure-pharmacokinetic considerations.

A method to establish the correlation between the reverse phase high performance liquid chromatographic retention of caffeine and its metabolites and their n-octanol/water partition coefficients is described. The log (P) values were always below zero, ranging from -0.02 to -2.03. The capacity factor quadratically back-extrapolated to 100% water eluent (k'w) was used as the index of lipophilicity. The compounds examined gave a good correlation (r greater than 0.99) with log (k'w) if considered in separate series, depending on the substituent position. For a structure-pharmacokinetic relationship study, correlations were found between the partition coefficient and some pharmacokinetic parameters, suggesting that for drugs that are widely metabolized, any predictions of their disposition from physicochemical characteristics are hazardous.

1-Octanol↗
PubMed1995

Determination of octanol-water partition coefficients by an HPLC method for anticonvulsant structure-activity studies.

Octanol-water partition coefficients have been measured and calculated for eight clinically relevant anticonvulsants. For some compounds, these are the first experimentally available log P values. For the remainder of the molecules, new values have been suggested. The utility of the micro shake-flask experimental method and the ALOGP calculational method in determining anticonvulsant log P values has been demonstrated.

1-Octanol↗
PubMed1995

Growth on octane alters the membrane lipid fatty acids of Pseudomonas oleovorans due to the induction of alkB and synthesis of octanol.

Growth of Pseudomonas oleovorans GPo1, which contains the OCT plasmid, on octane results in changes in the membrane phospholipid fatty acid composition. These changes were not found for GPo12, an OCT-plasmid-cured variant of GPo1, during growth in the presence or absence of octane, implying the involvement of OCT-plasmid-encoded functions. When recombinant strain GPo12(pGEc47) carrying the alk genes from the OCT plasmid was grown on octane, the cells showed the same changes in fatty acid composition as those found for GPo1, indicating that such changes result from induction and expression of the alk genes. This finding was corroborated by inducing GPo12(pGEc47) with dicyclopropylketone (DCPK), a gratuitous inducer of the alk genes. Further experiments showed that the increase of the mean acyl chain length of fatty acids is related to the expression of alkB, which encodes a major integral membrane protein, while the formation of trans unsaturated fatty acids mainly results from the effects of 1-octanol, an octane oxidation product.

1-Octanol↗
PubMed1988

Prediction of environmental fate and effects of heteroatomic polycyclic aromatics by QSARs: the position of n-octanol/water partition coefficients.

The HPLC and TLC retention, n-octanol/water partition coefficients (log Kow), bioconcentration factors, and acute toxicity data of 29 heteroatomic polycyclic aromatic hydrocarbons and 7 parent polycyclic aromatics were determined experimentally. For the same set of compounds, molecular weights, fragmental log Kow values, and molecular connectivities were calculated. Quantitation of the mathematical relationships between the variables was used to validate the predictive potential of various parameters. The importance of log Kow in predictive studies is highlighted. It is concluded that the internal concentration of a pollutant in the organism should be used as a parameter in future QSAR work.

1-Octanol↗
PubMed1996

A distinctive effect of CCCP on the transfer of erythromycin to 1-octanol: a possible model in promoting the intracellular antibiotic-accumulation through lipid in a staphylococcal cytoplasmic membrane.

Movement of erythromycin (EM), a basic antibiotic solute (pKa 8.6), in an aqueous buffer (pH7.6) at 37 degrees C into 1-octanol was found approximately twofold greater in the presence of another acidic and lipophilic solute, carbonylcyanide m-chlorophenylhydrazone (CCCP), when compared with the EM-movement in the absence of CCCP. CCCP appears to behave just like a carrier of EM, besides being a well-known inhibitor, such as the uncoupling agent of oxidative phosphorylation. The probability is discussed that such an analogous event takes place in the lipid layers of a bacterial-cell membrane.

1-Octanol↗
PubMed1998

Octanol-water partition of nonzwitterionic peptides: predictive power of a molecular size-based model.

A remarkably simple, molecular size-based model developed to predict octanol-water partition coefficients for organic compounds is tested on a set of 188 neutral peptides with available experimental partition data. Despite using only two parameters, it gives a promising correlation (r2 = 0.914; sigma = 0.455, F = 1978.0), and predictions are in a realistic range even for larger peptides (cyclosporin, melanotan, sandostatin) where common, overparametrized fragment methods become quite unreliable. Ion-pair partitioning and the extraction constant formalism is briefly reviewed to describe the sigmoidal lipophilicity profile of ionizable, nonzwitterionic peptides. It seems possible to extend the present model to estimate apparent partition coefficients measured around neutral pH and physiological conditions for monoionic peptides; however, as no standard conditions are yet defined and only relatively small number of experimental data are available, the situation here is more complex.

Models, Molecular↗