Measurement and prediction of hydrophobicity parameters for highly lipophilic compounds: application of the HPLC column-switching technique to measurement of log P of diarylpyrazines

Encapsulation and release of curcumin using an intact milk fat globule delivery system

Milk fat globule carriers were evaluated as an encapsulation system for curcumin. Partitioning is confirmed using fluorescence imaging. Release of curcumin under simulated gastrointestinal conditions and associated morphological changes to the carriers were evaluated.

Analogues of desferrioxamine B designed to attenuate iron-mediated neurodegeneration: synthesis, characterisation and activity in the MPTP-mouse model of Parkinson's disease

One dual-function (2) and one first-generation (9) conjugate of the Fe(iii) chelator desferrioxamine B (DFOB,1) showed significant rescue of neurons in the MPTP mouse model of Parkinson's disease.

Investigating biological activity spectrum for novel styrylquinazoline analogues

In this study, series of ring-substituted 2-styrylquinazolin-4(3H)-one and 4-chloro-2-styrylquinazoline derivatives were prepared. The syntheses of the discussed compounds are presented. The compounds were analyzed by RP-HPLC to determine lipophilicity. They were tested for their inhibitory activity on photosynthetic electron transport (PET) in spinach (Spinacia oleracea L.) chloroplasts. Primary in vitro screening of the synthesized compounds was also performed against four mycobacterial strains and against eight fungal strains. Several compounds showed biological activity comparable with or higher than that of the standard isoniazid. It was found that the electronic properties of the R substituent, and not the total lipophilicity of the compound, were decisive for the photosynthesis-inhibiting activity of tested compounds.

RP-HPLC determination of lipophilicity in series of quinoline derivatives

In the present paper we describe results on the synthesis and lipophilicity determination of a series of biologically active compounds based on their heterocyclic structure. For synthesis of styrylquinoline-based compounds we applied microwave irradiation and solid phase techniques. The correlation between RP-HPLC retention parameter log k (the logarithm of retention factor k) and log P data calculated in various ways is discussed, as well as, the relationships between the lipophilicity and the chemical structure of the studied compounds.

New Hydrophobicity Constants of Substituents in Pyrazine Rings Derived from RP-HPLC Study

Pyrazine derivatives show a wide range of biological activities. 1-Pyrazin-2-ylethan-1-ones have served as food flavourants, and together with pyrazine-2-carbonitriles have been widely used as intermediates in the synthesis of various heterocyclic compounds. In our laboratory, substituted pyrazine-2-carbonitriles and 1-pyrazin-2-ylethan-1-ones have been used as intermediates for the preparation of potential antifungal and antimycobacterial drugs. Using established methods, a library of pyrazine derivatives was synthesized. Homolytic alkylation of commercially available pyrazine-2-carbonitrile yielded a series of 5-alkylpyrazine-2-carbonitriles which were converted into the corresponding 1-(5-alkylpyrazin-2-yl)ethan-1-ones (5-alkyl-2-acetylpyrazines) via the Grignard reaction. Homolytic acetylation of pyrazine-2-carbonitrile yielded 5-acetylpyrazine-2-carbonitrile. Using the same procedure, 3-acetyl-5-tert-butylpyrazine-2-carbonitrile was obtained with 5-tert-butylpyrazine-2-carbonitrile as a starting material. The hydrophobicity of the compounds was determined both experimentally (RP-HPLC) and by computation (CS ChemOffice Ultra version 9.0, ACD/LogP version 1.0 and ACD/LogP version 9.04), and both the approaches were compared. New hydrophobicity constants π based on experimental results were derived. These constants are markedly different from tabulated constants π valid for benzene rings, and can be widely used in estimating physicochemical properties of new biologically active pyrazines.

Whole-molecule calculation of log p based on molar volume, hydrogen bonds, and simulated 13C NMR spectra

The prediction of Log P is usually accomplished using either substructure or whole-molecule approaches. However, these methods are complicated, and previous whole-molecule approaches have not been successful for the prediction of Log P in very complex molecules. The observed chemical shifts in nuclear magnetic resonance (NMR) spectroscopy are related to the electrostatics at the nucleus, which are influenced by solute-solvent interactions. The different solvation effects on a molecule by either water or methanol have a strong effect on the NMR chemical shift value. Therefore, the chemical shift values observed in an aqueous and organic solvent should correlate to Log P. This paper develops a rapid, objective model of Log P based on molar volume, hydrogen bonds, and differences in calculated 13C NMR chemical shifts for a diverse set of compounds. A partial least squares (PLS) model of Log P built on the sum of carbon chemical shift differences in water and methanol, molar volume, number of hydrogen bond donors and acceptors in 162 diverse compounds gave an r2 value of 0.88. The average r2 for 10 training models of Log P made from 90% of the data was 0.87+/-0.01. The average q2 for 10 leave-10%-out cross-validation test sets was 0.87+/-0.05.

Method for measuring the logarithm of the octanol-water partition coefficient by using short octadecyl-poly(vinyl alcohol) high-performance liquid chromatography columns

A simple, quick, versatile and inexpensive HPLC method to estimate the logarithm of the octanol-water partition coefficient (log Pow) employing a methanol-water gradient and a short octadecyl-poly(vinyl alcohol) (ODP) column is described. This method is different from published HPLC-based log Pow methods because it uses retention times from a rapid methanol-water gradient to directly generate log Pow estimates, rather than from a series of isocratic mixtures extrapolated to 100% water. These HPLC log Pow values have good precision and correlate well with traditional shake-flask log Pow values. If necessary, the log Pow determination (including replications) can easily be carried out using only a milligram of sample. By suppressing ionization of acids and bases by the use of a buffer in the aqueous phase, the method can measure the log Pow of neutral organic molecules at any pH between 2 and 13. The method can be used with impure material and is rapid, 7 min per run and 4 min equilibration; it lends itself to and has been utilized for high-throughput hydrophobicity determinations (we have now carried out thousands of HPLC log Pow measurements by this method).

High throughput physicochemical profiling for drug discovery

The drug development bottlenecks of attrition and development time are being addressed by acquiring a profile of the candidate's physicochemical and physiological properties during early discovery phases. This information assists selection and optimization of pharmaceutical properties in parallel with activity. High throughput methods to measure the properties: solubility, permeability, lipophilicity, pKa, stability and integrity are described and compared in this article. The underlying discovery requirements, needs and application strategies are discussed.

ElogD(oct): a tool for lipophilicity determination in drug discovery. 2. Basic and neutral compounds

We present an RP-HPLC method for the determination of the octanol-water distribution coefficients at pH 7.4, as log values, for neutral and basic drugs, which combines ease of operation with high accuracy. The method is shown to work for a training set of 90 molecules comprised largely of drugs, and it was also applied to a test set of 10 proprietary compounds. This work expands the applicability of the method presented in our earlier report, for the determination of logP(oct) for neutral compounds (J. Med. Chem. 2000, 43, 2922-2928), and it offers the same general features but widens the scope. Generally, the method (i) is compound sparing (< or =1 mL of a 50-100 microg/mL solution needed), (ii) is insensitive to concentration and phase ratio effects observed in some shake-flask determinations, (iii) is amenable to rapid determinations (< or = 20 min on average), (iv) is insensitive to impurities, (v) possesses a wide lipophilicity range (>7 log units), and (vi) offers a good accuracy, (vii) an excellent reproducibility, (viii) and an excellent potential for automation. To the best of our knowledge, a similar performance, on a set of noncongeneric drugs, has not been previously reported. We refer to the value generated via this method as ElogD(oct).

Reversed‐phase high‐performance liquid chromatography (RP‐HPLC) determination of lipophilicity of furocoumarins: Relationship with DNA interaction

The partition coefficient (P) of 82 furocoumarins and analogs (psoralens, angelicins, allopsoralens, 8-azapsoralens, angular furoquinolin-2-ones, sulfur and selenium isosters of psoralen and angelicin) has been determined by reversed-phase HPLC. The chromatographic behavior correlates well with the in vitro affinity of the compounds toward DNA.

ElogPoct: a tool for lipophilicity determination in drug discovery

We present an RP-HPLC method, for the determination of logPoct values for neutral drugs, which combines ease of operation with high accuracy and which has been shown to work for a set of 36 molecules comprised largely of drugs. The general features of the method are as follows: (i) compound sparing (< or = 1 mL of a 30-50 microg/mL solution needed), (ii) rapid determinations (20 min on average), (iii) low sensitivity to impurities, (iv) wide lipophilicity range (6 logPoct units), (v) good accuracy, (vi) excellent reproducibility. A linear free energy relationship (LFER) analysis, based on solvation parameters, shows that the method encodes the same information obtained from a shake-flask logPoct determination. To the best of our knowledge a similar performance, on a set of noncongeneric drugs, has not been previously reported. We refer to the value generated via this method as ElogPoct.