Lipophilicity - beyond octanol/water: a short comparison of modern technologies

Evaluation of the Lipophilicity of Angularly Condensed Diquino- and Quinonaphthothiazines as Potential Candidates for New Drugs

Lipophilicity is one of the most important properties of compounds required to estimate the absorption, distribution, and transport in biological systems, in addition to solubility, stability, and acid-base nature. It is crucial in predicting the ADME profile of bioactive compounds. The study assessed the usefulness of computational and chromatographic methods (thin-layer chromatography in a reversed-phase system, RP-TLC) for estimating the lipophilicity of 21 newly synthesized compounds belonging to diquinothiazines and quinonaphthiazines. In order to obtain reliable values of the relative lipophilicities of diquinothiazines and quinonaphthiazines, the partition coefficients obtained using different algorithms such as AlogPs, AClogP, AlogP, MLOGP, XLOGP2, XLOGP3, logP, and ClogP were compared with the chromatographic RM0 values of all the tested compounds measured by the experimental RP-TLC method (logPTLC). Additionally, logPTLC values were also correlated with other descriptors, as well as the predicted ADME and drug safety profiling parameters. The linear correlations of logPTLC values of the tested compounds with other calculated molecular descriptors such as molar refractivity, as well as ADME parameters (Caco-2 substrates, P-gp inhibitors, CYP2C19, and CYP3A4) generally show poor predictive power. Therefore, in silico ADME profiling can only be helpful at the initial step of designing these new candidates for drugs. The compliance of all discussed diquinothiazines and naphthoquinothiazines with the rules of Lipiński, Veber, and Egan suggests that the tested pentacyclic phenothiazine analogs have a chance to become therapeutic drugs, especially orally active drugs.

Computer-aided drug discovery of c-Abl kinase inhibitors from plant compounds against chronic myeloid leukemia

Chronic myeloid leukemia (CML) is a hematological malignancy characterized by the neoplastic transformation of hematopoietic stem cells, driven by the Philadelphia (Ph) chromosome resulting from a translocation between chromosomes 9 and 22. This Ph chromosome harbors the breakpoint cluster region (BCR) and the Abelson (ABL) oncogene (BCR-ABL1) which have a constitutive tyrosine kinase activity. However, the tyrosine kinase activity of BCR-ABL1 have been identified as a key player in CML initiation and maintenance through c-Abl kinase. Despite advancements in tyrosine kinase inhibitors, challenges such as efficacy, safety concerns, and recurring drug resistance persist. This study aims to discover potential c-Abl kinase inhibitors from plant compounds with anti-leukemic properties, employing drug-likeness assessment, molecular docking, in silico pharmacokinetics (ADMET) screening, density function theory (DFT), and molecular dynamics simulations (MDS). Out of 58 screened compounds for drug-likeness, 44 were docked against c-Abl kinase. The top hit compound (isovitexin) and nilotinib (control drug) were subjected to rigorous analyses, including ADMET profiling, DFT evaluation, and MDS for 100 ns. Isovitexin demonstrated a notable binding affinity (-15.492 kcal/mol), closely comparable to nilotinib (-16.826 kcal/mol), showcasing a similar binding pose and superior structural stability and reactivity. While these findings suggest isovitexin as a potential c-Abl kinase inhibitor, further validation through urgent in vitro and in vivo experiments is imperative. This research holds promise for providing an alternative avenue to address existing CML treatment and management challenges.Communicated by Ramaswamy H. Sarma.

The effect of intravenous lipid emulsion (ILE) on the pharmacokinetic/toxicokinetic dispositions of ivermectin and carprofen in rabbits

Intravenous lipid emulsion (ILE) has been widely used as an effective antidote in both veterinary and human medicine for the treatment of acute intoxications caused by drugs and pesticides with high lipid solubility. This study was conducted to investigate the effect of ILE co-administration on the kinetic dispositions of ivermectin (IVM) and carprofen (CRP) following intravenous bolus administration at subtoxic doses in rabbits.Twenty-four male New Zealand rabbits weighing 2.78 ± 0.2 kg were used in this study. Rabbits were divided into four groups (Group 1: IVM and Group 2: IVM + ILE or Group 3: CRP and Group 4: CRP + ILE), each group consisting of 6 animals. In the IVM study, Group 1 received IVM (0.6 mg/kg) alone while Group 2 received IVM (0.6 mg/kg) and ILE (2.5 ml/kg). In the CRP study, Group 3 received CRP (12 mg/kg) alone while Group 4 received CRP (12 mg/kg) and ILE (2.5 ml/kg). In both drug groups, ILE was administered 3 times as an i.v. bolus at the 10th min and repeated 4th and 8th h after the drug administration. Blood samples were collected from the auricular vein at various times after drug administration. The drug concentrations in plasma samples were determined by high-pressure liquid chromatography. Kinetic parameters were calculated using a non-compartmental model for both CRP and IVM.The C0 and area under the concentration-time curve from zero up to ∞ (AUC0-∞) values were significantly greater with ILE co-administration (2136 ng/ml and 360.84 ng.d/ml) compared to the IVM alone (1340.63 ng/ml and 206 ng.d/ml), respectively. Moreover, the volume of distribution (Vdss) and clearance (Cl) of IVM were reduced by approximately 42% and 46% with ILE co-administration compared to IVM alone resulting in a reduction of the distribution and slower elimination, respectively. Similar differences in C0, and Vdss values were also observed in CRP with ILE co-administration compared to CRP alone. ILE co-administration changed significantly the kinetic profile of both IVM and CRP in rabbits, supporting the lipid sink theory in which highly lipid-soluble compounds are absorbed into the lipid phase of plasma from peripheral organs such as the heart and brain affected by the acute toxicity of the compounds.

Energy-entropy multiscale cell correlation method to predict toluene-water log P in the SAMPL9 challenge

The energy-entropy multiscale cell correlation (EE-MCC) method is used to calculate toluene-water log P values of 16 drug molecules in the SAMPL9 physical properties challenge. EE-MCC calculates the free energy, energy and entropy from molecular dynamics (MD) simulations of the water and toluene solutions. Specifically, MCC evaluates entropy by partitioning the system into cells of correlated atoms at multiple length scales and further partitioning the local coordinates into energy wells, yielding vibrational and topographical terms from the energy-well sizes and probabilities. The log P values calculated by EE-MCC using three 200 ns MD simulations have a mean average error of 0.82 and standard error of the mean of 0.97 versus experiment, which is comparable with the best methods entered in SAMPL9. The main contribution to log P is from energy. Less polar drugs have more favourable energies of transfer. The entropy of transfer consists of increased solute vibrational and conformational terms in toluene due to weaker interactions, fewer solute positions in the larger-molecule solvent, reduced water vibrational entropy, negligible change in toluene vibrational entropy, and gains in solvent orientational entropy. The solvent entropy contributions here may be slightly underestimated because software limitations and statistical fluctuations meant that only the first shell could be included while averaged over the whole solution. Nonetheless, such issues will be addressed in future software to offer a general method to calculate entropy directly from MD simulation and to provide molecular understanding or guide system design.

Prediction of toluene/water partition coefficients in the SAMPL9 blind challenge: assessment of machine learning and IEF-PCM/MST continuum solvation models

In recent years the use of partition systems other than the widely used biphasic n-octanol/water has received increased attention to gain insight into the molecular features that dictate the lipophilicity of compounds. Thus, the difference between n-octanol/water and toluene/water partition coefficients has proven to be a valuable descriptor to study the propensity of molecules to form intramolecular hydrogen bonds and exhibit chameleon-like properties that modulate solubility and permeability. In this context, this study reports the experimental toluene/water partition coefficients (log Ptol/w) for a series of 16 drugs that were selected as an external test set in the framework of the Statistical Assessment of the Modeling of Proteins and Ligands (SAMPL) blind challenge. This external set has been used by the computational community to calibrate their methods in the current edition (SAMPL9) of this contest. Furthermore, the study also investigates the performance of two computational strategies for the prediction of log Ptol/w. The first relies on the development of two machine learning (ML) models, which are built up by combining the selection of 11 molecular descriptors in conjunction with either the multiple linear regression (MLR) or the random forest regression (RFR) model to target a dataset of 252 experimental log Ptol/w values. The second consists of the parametrization of the IEF-PCM/MST continuum solvation model from B3LYP/6-31G(d) calculations to predict the solvation free energies of 163 compounds in toluene and benzene. The performance of the ML and IEF-PCM/MST models has been calibrated against external test sets, including the compounds that define the SAMPL9 log Ptol/w challenge. The results are used to discuss the merits and weaknesses of the two computational approaches.

A Study of Absorption and Selected Molecular Physicochemical Properties of Some Antipsychotic Drugs

Antipsychotic drugs are commonly prescribed for different mental disorders and can be classified into two main groups: the first which contain originally developed antipsychotics of the first generation or typical antipsychotics and the other group with newly developed antipsychotics or atypical antipsychotics of the second generation. In this study, eleven antipsychotic drugs (chlorpromazine, flupentixol, haloperidol, zuclopenthixol, aripiprazole, clozapine, olanzapine, quetiapine, risperidone, sertindole, ziprasidone) were investigated to evaluate significance of their molecular physicochemical properties (lipophilicity, aqueous solubility, polar surface area, molecular weight, volume value and acidity) for their bioavailability. Relationships between literature available intestinal absorption data of antipsychotic drugs and their lipophilicity descriptor with one additional molecular descriptor, investigated using multiple linear regression analysis provided high correlations for molecular descriptors, Mw, Vol, pKa, as additional independent variables. Values of correlation coefficients (R2) were ranged from 0.951 (for Vol) above 0.944 (for Mw) to 0.923 (for pKa).

Structural Basis of 2-Phenylamino-4-phenoxyquinoline Derivatives as Potent HIV-1 Non-Nucleoside Reverse Transcriptase Inhibitors

New target molecules, namely, 2-phenylamino-4-phenoxyquinoline derivatives, were designed using a molecular hybridization approach, which was accomplished by fusing the pharmacophore structures of three currently available drugs: nevirapine, efavirenz, and rilpivirine. The discovery of disubstituted quinoline indicated that the pyridinylamino substituent at the 2-position of quinoline plays an important role in its inhibitory activity against HIV-1 RT. The highly potent HIV-1 RT inhibitors, namely, 4-(2′,6′-dimethyl-4′-formylphenoxy)-2-(5″-cyanopyridin-2″ylamino)quinoline (6b) and 4-(2′,6′-dimethyl-4′-cyanophenoxy)-2-(5″-cyanopyridin-2″ylamino)quinoline (6d) exhibited half-maximal inhibitory concentrations (IC50) of 1.93 and 1.22 µM, respectively, which are similar to that of nevirapine (IC50 = 1.05 µM). The molecular docking results for these two compounds showed that both compounds interacted with Lys101, His235, and Pro236 residues through hydrogen bonding and interacted with Tyr188, Trp229, and Tyr318 residues through π–π stacking in HIV-1 RT. Interestingly, 6b was highly cytotoxic against MOLT-3 (acute lymphoblastic leukemia), HeLA (cervical carcinoma), and HL-60 (promyeloblast) cells with IC50 values of 12.7 ± 1.1, 25.7 ± 0.8, and 20.5 ± 2.1 µM, respectively. However, 6b and 6d had very low and no cytotoxicity, respectively, to-ward normal embryonic lung (MRC-5) cells. Therefore, the synthesis and biological evaluation of 2-phenylamino-4-phenoxyquinoline derivatives can serve as an excellent basis for the development of highly effective anti-HIV-1 and anticancer agents in the near future.

Assessment of Lipophilicity Descriptors of Selected NSAIDs Obtained at Different TLC Stationary Phases

Lipophilicity study of selected NSAIDs, the group of the bioactive compounds usually used in humans and animals medicine, with the use of experimental and calculation methods was evaluated. LogP values are proposed and compared as descriptors of the lipophilicity of eleven compounds (from oxicams and coxibs). Obtained data were designated by thin-layer chromatography (TLC) in various chromatographic conditions, with stationary phases with different properties. The mobile phase systems were prepared by mixing the respective amounts of water and organic modifier, methanol and acetone, in the range of 30 to 80% (v/v) in 5% increments. Retention parameters (RF, RM and RM0) were calculated and statistically evaluated to establish correlations. All experimentally determined RM0 values were compared with partition coefficients obtained by computational methods using linear regression analysis. Moreover, in order to extract information about the lipophilicity of compounds from large retention datasets, two chemometric approaches, namely principal component analysis (PCA) and cluster analysis (CA) were carried out. Established models of lipophilicity may have the potential to predict the biological activity of a number of drugs. The presented knowledge may also be of use during drug discovery processes, broadening the knowledge of potential ways to modify the physicochemical properties of chemical compounds.

A Fully Integrated Assay Panel for Early Drug Metabolism and Pharmacokinetics Profiling

Evaluation and optimization of physicochemical and metabolic properties of compounds are a crucial component of the drug development process. Continuous access to this information during the design-make-test-analysis cycle enables identification of chemical entities with suitable properties for efficient project progression. In this study, we describe an integrated and automated assay panel (DMPK Wave 1) that informs weekly on lipophilicity, solubility, human plasma protein binding, and metabolic stability in rat hepatocytes and human liver microsomes. All assays are running in 96-well format with ultraperformance liquid chromatography-mass spectrometry (MS)/MS as read-out. A streamlined overall workflow has been developed by optimizing all parts of the process, including shipping of compounds between sites, use of fit-for-purpose equipment and information systems, and technology for compound requesting, data analysis, and reporting. As a result, lead times can be achieved that well match project demands across sites independently of where compounds are synthesized. This robust screening strategy is run on a weekly basis and enables optimization of structure-activity relationships in parallel with DMPK properties to allow efficient and informed decision making.

The Application of CA and PCA to the Evaluation of Lipophilicity and Physicochemical Properties of Tetracyclic Diazaphenothiazine Derivatives

The subject of the study was 11 new synthetized tetracyclic diazaphenothiazine derivatives. Using thin-layer chromatography in a reverse phase system (RP-TLC), their R _M0 lipophilicity parameter was determined. The mobile phase was composed of 0.2 M Tris buffer (pH = 7.4) and acetone (POCH S.A., Gliwice, Poland) in different concentrations. Using computer programs, based on different computational algorithms, theoretical values of lipophilicity (AClogP, ALOGP, ALOGPs, miLogP, MLOGP, XLOGP2, and XLOGP3) as well as molecular descriptors (molecular weight, volume of a molecule, dipole moment, polar surface, and energy of HOMO orbitals and LUMO orbitals) and parameters of biological activity: human intestinal absorption (HIA), plasma protein binding (PPB), and blood-brain barrier (BBB), were determined. The correlations between the experimental values of lipophilicity and theoretically calculated lipophilic values and also between experimental values of lipophilicity and values of physicochemical or biological properties were assessed. A certain relationship between structure and lipophilicity was found. On the other hand, the relationships between R _M0 and physicochemical or biological properties were not statistically significant and therefore unusable. For all analysed values, an analysis of similarities and principal component analyses were also made. The obtained dendrograms for the analysis of lipophilicity and physicochemical and biological properties indicate the relationship between experimental values of lipophilicity and structure in the case of theoretical lipophilicity values only. PCA, on the other hand, showed that ALOGP, MLOGP, miLogP, and BBB and molar volume have the largest share in the description of the entire system. Distribution of compounds on the area of factors also indicates the connections between them related to their structure.

Fine-Tuning the Activation Mode of an 1,3-Indandione-Based Ruthenium(II)-Cymene Half-Sandwich Complex by Variation of Its Leaving Group

Fine-tuning of the properties of a recently reported 1,3-indandione-based organoruthenium complex is attempted to optimize the stability under physiological conditions. Previous work has shown its capacity of inhibiting topoisomerase IIα; however, fast aquation leads to undesired reactions and ligand cleavage in the blood stream before the tumor tissue is reached. Exchange of the chlorido ligand for six different N-donor ligands resulted in new analogs that were stable at pH 7.4 and 8.5. Only a lowered pH level, as encountered in the extracellular space of the tumor tissue, was capable of aquating the complexes. The 50% inhibitory concentration (IC₅₀) values in three human cancer cell lines differed only slightly, and their dependence on the utilized leaving group was smaller than what would be expected from their differences in cellular accumulation, but in accordance with the very minor variation revealed in measurements of the complexes’ lipophilicity.

Investigation of Hydro-Lipophilic Properties of N-Alkoxyphenylhydroxynaphthalenecarboxamides †

The evaluation of the lipophilic characteristics of biologically active agents is indispensable for the rational design of ADMET-tailored structure⁻activity models. N-Alkoxy-3-hydroxynaphthalene-2-carboxanilides, N-alkoxy-1-hydroxynaphthalene-2-carboxanilides, and N-alkoxy-2-hydroxynaphthalene-1-carboxanilides were recently reported as a series of compounds with antimycobacterial, antibacterial, and herbicidal activity. As it was found that the lipophilicity of these biologically active agents determines their activity, the hydro-lipophilic properties of all three series were investigated in this study. All 57 anilides were analyzed using the reversed-phase high-performance liquid chromatography method for the measurement of lipophilicity. The procedure was performed under isocratic conditions with methanol as an organic modifier in the mobile phase using an end-capped non-polar C₁₈ stationary reversed-phase column. In the present study, a range of software lipophilicity predictors for the estimation of clogP values of a set of N-alkoxyphenylhydroxynaphthalenecarboxamides was employed and subsequently cross-compared with experimental parameters. Thus, the empirical values of lipophilicity (logk) and the distributive parameters (π) were compared with the corresponding in silico characteristics that were calculated using alternative methods for deducing the lipophilic features. To scrutinize (dis)similarities between the derivatives, a PCA procedure was applied to visualize the major differences in the performance of molecules with respect to their lipophilic profile, molecular weight, and violations of Lipinski’s Rule of Five.

Confocal Raman Microscopy for in Situ Measurement of Phospholipid-Water Partitioning into Model Phospholipid Bilayers within Individual Chromatographic Particles

The phospholipid-water partition coefficient is a commonly measured parameter that correlates with drug efficacy, small-molecule toxicity, and accumulation of molecules in biological systems in the environment. Despite the utility of this parameter, methods for measuring phospholipid-water partition coefficients are limited. This is due to the difficulty of making quantitative measurements in vesicle membranes or supported phospholipid bilayers, both of which are small-volume phases that challenge the sensitivity of many analytical techniques. In this work, we employ in situ confocal Raman microscopy to probe the partitioning of a model membrane-active compound, 2-(4-isobutylphenyl) propionic acid or ibuprofen, into both hybrid- and supported-phospholipid bilayers deposited on the pore walls of individual chromatographic particles. The large surface-area-to-volume ratio of chromatographic silica allows interrogation of a significant lipid bilayer area within a very small volume. The local phospholipid concentration within a confocal probe volume inside the particle can be as high as 0.5 M, which overcomes the sensitivity limitations of making measurements in the limited membrane areas of single vesicles or planar supported bilayers. Quantitative determination of ibuprofen partitioning is achieved by using the phospholipid acyl-chains of the within-particle bilayer as an internal standard. This approach is tested for measurements of pH-dependent partitioning of ibuprofen into both hybrid-lipid and supported-lipid bilayers within silica particles, and the results are compared with octanol-water partitioning and with partitioning into individual optically trapped phospholipid vesicle membranes. Additionally, the impact of ibuprofen partitioning on bilayer structure is evaluated for both within-particle model membranes and compared with the structural impacts of partitioning into vesicle lipid bilayers.

Lipophilicity assessement in drug discovery: Experimental and theoretical methods applied to xanthone derivatives

For the last several years, searching of new xanthone derivatives (XDs) with potential pharmacological activities has remained one of the main areas of interest of our group. The optimization of biological activity and drug-like properties of hits and leads is crucial at early stage of the drug discovery pipeline. Lipophilicity is one of the most important drug-like properties having a great impact in both pharmacokinetics and pharmacodynamics processes. In this work, we describe the lipophilicity of a small library of bioactive XDs, previously synthesized by our group, using different methods: computational, vortex-assisted liquid-liquid microextraction coupled with high-performance liquid chromatography (VALLME-HPLC), reversed-phase high-performance thin layer chromatography (RP-HPTLC), reversed-phase high-performance liquid chromatography (RP-HPLC), and biomembrane model by the partition between micelles and aqueous phase. The different results obtained by the used methods were compared and discussed. The methodologies and data gathered in this study will expand the investigation of lipophilicity of XDs, an important class of compounds in medicinal chemistry.

A greener and efficient access to substituted four- and six-membered sulfur-bearing heterocycles

The regioselective functionalization of four- and six-membered cyclic sulfones was investigated using a lithiation/functionalization strategy.

Evaluation of the ability of arsenic species to traverse cell membranes by simple diffusion using octanol-water and liposome-water partition coefficients

Arsenic metabolism in living organisms is dependent on the ability of different arsenic species to traverse biological membranes. Simple diffusion provides an alternative influx and efflux route to mediated transport mechanisms that can increase the amount of arsenic available for metabolism in cells. Using octanol-water and liposome-water partition coefficients, the ability of arsenous acid, arsenate, methylarsonate, dimethylarsinate, thio-methylarsonate, thio-dimethylarsinic acid, arsenotriglutathione and monomethylarsonic diglutathione to diffuse through the lipid bilayer of cell membranes was investigated. Molecular modelling of arsenic species was used to explain the results. All arsenic species with the exception of arsenate, methylarsonate and thio-methylarsonate were able to diffuse through the lipid bilayer of liposomes, with liposome-water partition coefficients between 0.04 and 0.13. Trivalent arsenic species and thio-pentavalent arsenic species showed higher partition coefficients, suggesting that they can easily traverse cell membranes by passive simple diffusion. Given the higher toxicity of these species compared to oxo-pentavalent arsenic species, this study provides evidence supporting the risk associated with human exposure to trivalent and thio-arsenic species.

Effects of polar κ receptor agonists designed for the periphery on ATP-induced Ca2+ release from keratinocytes

The very polar pyridylmethyl derivative 5a (log D_7.4 = 1.1) represents a potent and selective full κ-opioid receptor agonist (K_i = 0.13 nM, EC₅₀ = 33 nM), which reduced the release of Ca²⁺-ions into the cytoplasm in human keratinocytes.

Concise synthesis of a new triterpenoid saponin from the roots of Gypsophila oldhamiana and its derivatives as α-glucosidase inhibitors

The natural triterpenoid saponin 1 and its derivatives 2–3 were synthesized and exhibited potent inhibitory activities against α-glucosidase in vitro.

Evaluation of angiotensin-converting enzyme inhibitor's absorption with retention data of micellar thin-layer chromatography and suitable molecular descriptor

Twelve angiotensin-converting enzyme (ACE) inhibitors were studied to evaluate correlation between their absorption (ABS) data available in the literature (22-96%) and hydrophobicity parameters (km and Pm/w) obtained in micellar thin-layer chromatography (MTLC) using Brij 35. The theoretical considerations showed that the geometric molecular descriptor-volume value (Vol) should be considered as an independent variable simultaneously with calculated hydrophobicity parameters in multiple linear regression analysis to obtain reliable correlation between ACE inhibitor's absorption and lipophilicity (calculated KOWWINlog P) and that captopril should be excluded from further correlations. The results of MTLC confirmed that between the two hydrophobicity parameters km and Pm/w, for absorption prediction of 11 ACE inhibitors, the micelle-water partition coefficient Pm/w provided higher correlation (R(2) = 0.756), while for the km parameter R(2) = 0.612 was obtained. The micelle-water partition coefficient Pm/w could be considered as analogous to hydrophobicity parameter C0 from reversed-phase thin-layer chromatography. Dissimilar retention behavior of lisinopril indicated its lowest non-polar interaction with micelle, because of its di-acid form. The proposed model which included ACE inhibitors on the opposite site of lipophilicity-lisinopril and fosinopril (KOWWINlog P = -0.96 and KOWWINlog P = 6.61, respectively), both with similar absorption values (25 and 36%, respectively), could indicate that absorption of investigated compounds occurs via two different mechanisms: active and passive transport.

Analysis of Physicochemical Properties for Drugs of Natural Origin

The impact of time, therapy area, and route of administration on 13 physicochemical properties calculated for 664 drugs developed from a natural prototype was investigated. The mean values for the majority of properties sampled over five periods from pre-1900 to 2013 were found to change in a statistically significant manner. In contrast, lipophilicity and aromatic ring count remained relatively constant, suggesting that these parameters are the most important for successful prosecution of a natural product drug discovery program if the route of administration is not focused exclusively on oral availability. An examination by therapy area revealed that anti-infective agents had the most differences in physicochemical property profiles compared with other areas, particularly with respect to lipophilicity. However, when this group was removed, the variation between the mean values for lipophilicity and aromatic ring count across the remaining therapy areas was again found not to change in a meaningful manner, further highlighting the importance of these two parameters. The vast majority of drugs with a natural progenitor were formulated for either oral and/or injectable administration. Injectables were, on average, larger and more polar than drugs developed for oral, topical, and inhalation routes.

Evaluation of the lipophilicity of selected sunscreens--a chemometric analysis of thin-layer chromatographic retention data

The lipophilicities of 22 selected sunscreens, preservatives, and vitamins used in topical skin products were measured by thin-layer chromatography. Lipophilicity was calculated in silico from the sunscreen molecular structures and compared to the experimental octanol/water partition coefficients found in the literature. The retention of the compounds was investigated on an RP-18 stationary phase with mobile phases consisting of water and one of six organic modifiers (dioxane, tetrahydrofuran, acetone, acetonitrile, methanol, and dimethylformamide) at different concentrations. The theoretical lipophilicities were calculated by several computational algorithms and the results of these calculations were compared using cluster analysis. The results showed that two out of the six investigated organic modifiers (dioxane and acetone) may be used to estimate the octanol/water partition coefficients of highly lipophilic compounds having lipophilicities that cannot be measured directly by the shake-flask method.

Theoretical and experimental study on lipophilicity and wound healing activity of ginger compounds

OBJECTIVE

To correlate the chromatographic and computational method to calculate lipophilicity of selected ginger compounds and to observe the effects of log P on wound healing.

METHODS

Mixtures of acetonitrile and water with acetonitrile content between 95% and 50% v/v in 5% increments were kept separately in 10 different chromatographic chambers, saturated with solvent for 2 h. Spots were observed under UV light at λ=254 nm p-anisaldehyde used as a spraying reagent. Theoretical calculation was done using the Alogps 2.1 online program at www.vcclab.org/lab/alogps. For percentage wound contraction, five groups of animal (mice) (25-30 g) of either sex were selected. Wound were created on dorsal surface of animals using toothed forceps, scalpel and pointed scissors. The wound areas were calculated using vernier caliper. After making wound mice were orally administered 35 mg/kg 6-shogoal, 6-gingerol, 8-gingerol and 10-gingerol respectively. Group E as the control group received tap water.

RESULTS

The lipophilicity values determined in thin layer chromatography were correlated with the theoretically calculated various log P by linear regression analysis. Significant correlations were found between log P values calculated by software program and the experimental reversed-phase thin-layer chromatography data. Order of wound healing property of ginger compounds is directly dependent on lipophilicity i.e. more lipophilic compound has highest activity.

CONCLUSIONS

Experimentally determined lipophilicity (R MO) values were correlated with log P determined by software's and found satisfactory. Lipophilicity (R MO) is a useful parameter for the determination and prediction of biological activity of ginger compounds.

Zone fluidics for measurement of octanol-water partition coefficient of drugs

A novel zone fluidics (ZF) system for the determination of the octanol-water partition coefficient (Pow) of drugs was developed. The ZF system consisted of a syringe pump with a selection valve, a holding column, a silica capillary flow-cell and an in-line spectrophotometer. Exact microliter volumes of solvents (octanol and phosphate buffer saline) and a solution of the drug, sandwiched between air segments, were sequentially loaded into the vertically aligned holding column. Distribution of the drug between the aqueous and octanol phases occurred by the oscillation movement of the syringe pump piston. Phase separation occurred due to the difference in densities. The liquid zones were then pushed into the detection flow cell. In this method, absorbance measurements in only one of the phase (octanol or aqueous) were employed, which together with the volumes of the solvents and pure drug sample, allowed the calculation of the Pow. The developed system was applied to the determination of the Pow of some common drugs. The log (Pow) values agreed well with a batch method (R(2)=0.999) and literature (R(2)=0.997). Standard deviations for intra- and inter-day analyses were both less than 0.1log unit. This ZF system provides a robust and automated method for screening of Pow values in the drug discovery process.

Linear and nonlinear quantitative structure-property relationship modelling of skin permeability

In this work, quantitative structure-property relationship (QSPR) models were developed to estimate skin permeability based on theoretically derived molecular descriptors and a diverse set of experimental data. The newly developed method combining modified particle swarm optimization (MPSO) and multiple linear regression (MLR) was used to select important descriptors and develop the linear model using a training set of 225 compounds. The adaptive neuro-fuzzy inference system (ANFIS) was used as an efficient nonlinear method to correlate the selected descriptors with experimental skin permeability data (log Kp). The linear and nonlinear models were assessed by internal and external validation. The obtained models with three descriptors show good predictive ability for the test set, with coefficients of determination for the MPSO-MLR and ANFIS models equal to 0.874 and 0.890, respectively. The QSPR study suggests that hydrophobicity (encoded as log P) is the most important factor in transdermal penetration.

Design of new arylamino-2-ethane-1,1-diyl- and benzoxazole-2-methylene-bisphosphonates vs cytotoxicity and chronic inflammation diseases. From hydrophobicity prediction to synthesis and biological evaluation

A general synthetic approach to two new series of methylenebisphosphonates: arylamino-2-ethane-1,1-diyl- and benzoxazole-2-methylenebisphosphonates is presented. Acid hydrolysis of selected BPs was undertaken to give the corresponding bisphosphonic acid (BP-acid). Next, the prediction of the permeability (hydrophobicity) of the target compounds was measured, by a combination of RP-HPLC and computational techniques, to study the capacity of transporting the molecule through cellular membranes. Cytotoxicity/growth inhibition of 50% (GI(50), mg/L) and antichronic inflammation properties of the products were evaluated. Later on, a comparison of the pharmacological results with water-octanol partition coefficients (log K(OW)) of the compounds was also reported.

Drug penetration across the blood-brain barrier: an overview

The brain is one of the most protected organs in the body. There are two key barriers that control the access of endogenous substances and xenobiotics (drugs or toxins) to the CNS. These physiological structures are the blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier. The BBB represents the main determinant of the effective delivery of drugs to the CNS. Good access through the BBB is essential if the target site is located within the CNS or, in contrast, can be a disadvantage if adverse reactions occur at central level. The development of new drugs targeted to the CNS requires a better knowledge of the factors affecting BBB permeation as well as in vitro and in silico predictive tools to optimize screening, and to reduce the attrition rate at later stages of drug development. This review discusses the particular characteristics of the biology and physiology of the BBB with respect to the permeation and distribution of drugs into the brain. The factors affecting rate, extent and distribution into the brain are discussed and a brief description of the in silico, in vitro, in situ and in vivo methods used to measure BBB transport are presented. Finally, the lastest proposals and strategies to enhance transport across the BBB of new CNS drugs are summarized.

Exploiting micelle-driven coordination to evaluate the lipophilicity of molecules

We present a systematic study based on the calculation of complexation constants between a Zn-complex solubilized in Triton X-100 micellar solutions and a series of linear mono- and dicarboxylic acids, under physiological pH conditions, that allowed the evaluation of the lipophilicity of these molecules. This empirical lipophilicity parameter describes conveniently the partition of organic molecules between hydrophobic microdomains and water. The results can be used to predict the lipophilicity of molecules with similar structure and allows the distinction of intrinsic contributions of the carboxylates and of the methylene groups to the lipophilicity of the molecule.

Exploring the interplay of physicochemical properties, membrane permeability and giardicidal activity of some benzimidazole derivatives

This study evaluated the relationship between the physicochemical properties, membrane permeability and in vitro giardicidal activity of twenty nine benzimidazole derivatives (1-7n). The retention time data from reverse phase high performance chromatography (RP-HPLC) were used to estimate aqueous solubility and lipophilicity of these compounds. The apparent permeability was determined using Caco-2 cell monolayer. The calculation of some descriptors, such as Clog P, PSA, was performed using ACD labs software. For benzimidazole derivatives with NHCOOCH(3), CH(3), NH(2), SH and SCH(3) groups at the 2-position, a quadratic type of regression model was obtained with giardicidal activity and aqueous solubility or lipophilicity. On the other hand, giardicidal activity of 2-(trifluoromethyl)-1H-benzimidazole derivatives was influenced by lipophilicity, hydrogen bond donors and molecular volume but it was not determined by their apparent permeability in Caco-2 cell line.

Influence of molecular properties on oral bioavailability of lipophilic drugs - mapping of bulkiness and different measures of polarity

The biopharmaceutical assessment of new drug candidates based on their chemical structure is important in drug discovery and development. The scope of this study is to focus on lipophilic drugs and to clarify the role of their chemical predictors on oral bioavailability in humans. First their chemical properties were calculated from molecular modeling and the bioavailability data was obtained from the literature. The data was then analyzed by a partial least square method including non-linear terms. Significant coefficients were identified from a group of polarity- and solubility-related properties. Contour plots were constructed mapping molecular weight together with different polarity factors. Depending on the molecular weight a maximal bioavailability was found at solubility parameters of about 31-35 (J/cm(3))(1/2) and HLB values of roughly 4-12. The mapping of lipophilic drugs also revealed that a solubility parameter of less than 20 (J/cm(3))(1/2) or a HLB of smaller than unity is critical for the drug-likeness of new compounds.