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.

Evaluation of the Usefulness of Topological Indices for Predicting Selected Physicochemical Properties of Bioactive Substances with Anti-Androgenic and Hypouricemic Activity

Due to the observed increase in the importance of computational methods in determining selected physicochemical parameters of biologically active compounds that are key to understanding their ADME/T profile, such as lipophilicity, there is a great need to work on accurate and precise in silico models based on some structural descriptors, such as topological indices for predicting lipophilicity of certain anti-androgenic and hypouricemic agents and their derivatives, for which the experimental lipophilicity parameter is not accurately described in the available literature, e.g., febuxostat, oxypurinol, ailanthone, abiraterone and teriflunomide. Therefore, the following topological indices were accurately calculated in this paper: Gutman (M, Mν), Randić (0χ, 1χ, 0χν, 1χν), Wiener (W), Rouvray-Crafford (R) and Pyka (A, 0B, 1B) for the selected anti-androgenic drugs (abiraterone, bicalutamide, flutamide, nilutamide, leflunomide, teriflunomide, ailanthone) and some hypouricemic compounds (allopurinol, oxypurinol, febuxostat). Linear regression analysis was used to create simple linear correlations between the newly calculated topological indices and some physicochemical parameters, including lipophilicity descriptors of the tested compounds (previously obtained by TLC and theoretical methods). Our studies confirmed the usefulness of the obtained linear regression equations based on topological indices to predict ADME/T important parameters, such as lipophilicity descriptors of tested compounds with anti-androgenic and hypouricemic effects. The proposed calculation method based on topological indices is fast, easy to use and avoids valuable and lengthy laboratory experiments required in the case of experimental ADME/T studies.

Assessment of Lipophilicity Parameters of Antimicrobial and Immunosuppressive Compounds

Lipophilicity in addition to the solubility, acid-base character and stability is one of the most important physicochemical parameters of a compound required to assess the ADMET properties (absorption, distribution, metabolism, excretion and toxicity) of a bioactive molecule. Therefore, the subject of this work was to determine the lipophilicity parameters of selected antimicrobial and immunosuppressive compounds such as delafloxacin, linezolid, sutezolid, ceftazidime, everolimus and zotarolimus using thin-layer chromatography in reversed phase system (RP-TLC). The chromatographic parameters of lipophilicity (R_MW) for tested compounds were determined on different stationary phases: RP18F₂₅₄, RP18WF₂₅₄ and RP2F₂₅₄ using ethanol, acetonitrile, and propan-2-ol as organic modifiers of mobile phases used. Chromatographically established R_MW values were compared with partition coefficients obtained by different computational methods (AlogPs, AClogP, AlogP, MlogP, XlogP2, XlogP3, logP_KOWWIN, ACD/logP, milogP). Both cluster and principal component analysis (CA and PCA) of the received results allowed us to compare the lipophilic nature of the studied compounds. The sum of ranking differences analysis (SRD) of all lipophilicity parameters was helpful to select the most effective method of determining the lipophilicity of the investigated compounds. The presented results demonstrate that RP-TLC method may be a good tool in determining the lipophilic properties of studied substances. Obtained lipophilic parameters of the compounds can be valuable in the design of their new derivatives as efficient antimicrobial and immunosuppressive agents.

Comparison of the lipophilicity parameters of drospirenone and lynestrenol

Celem niniejszej pracy była analiza chromatograficzna dwóch związków steroidowych; drospirenonu i linestrenolu będących przedstawicielami grupy odpowiednio pro- i gestagenów oraz zastosowanie jej do wyznaczania parametrów lipofilowości obu tych związków. Zostały przebadane różne układy chromatograficzne złożone z płytek chromatograficznych pokrytych żelem krzemionkowym RP18F254 i RP18WF254 oraz trzech binarnych mieszanin jako faz ruchomych, takich jak metanol-woda, acetonitryl-woda i propan-2-ol-woda o zawartości modyfikatora organicznego w każdej z nich mieszczącej się w zakresie od 50% do 90% lub odpowiednio od 40% do 90%. Otrzymane na drodze licznych analiz chromatograficznych wartości RF drospirenonu i linestrenolu, które zostały następnie przeliczone na wartości parametru RM, posłużyły do wyznaczenia doświadczalnej wartości parametru lipofilowości tych związków w postaci RMW. Dodatkowo otrzymane chromatograficzne parametry lipofilowości porównano z teoretycznymi wartościami współczynnika podziału (logP) drospirenonu i linestrenolu uzyskanymi na podstawie różnych algorytmów obliczeniowych w formie AlogP, AlogPs, AClogP, MlgP, xlogP2 i xlogP3 oraz odpowiednio z eksperymentalną wartością logP oznaczoną jako logPexp dostępną dla jednego z nich tj. drospirenonu. W wyniku przeprowadzonych badań chromatograficznych oraz analizy wszystkich wyników parametrów lipofilowości, stwierdzono przydatność chromatografii cienkowarstwowej w zastosowanych układach złożonych z płytek RP18F254 i RP18W F254 oraz faz ruchomych o składzie metanol-woda, acetonitryl-woda oraz propan-2-ol-woda do wyznaczania doświadczalnej wartości parametru lipofilowości drospirenonu oraz linestrenolu w postaci RMW. Ponadto zaprezentowane w pracy badania świadczą o tym, że wybrane indeksy topologiczne związków biologicznie aktywnych, w tym o strukturze steroidowej jak drospirenon i linestrenol mogą być cenne w określaniu korelacji pomiędzy ich strukturą a właściwościami, w tym również lipofilowymi. Stwierdzono, że zaproponowana w powyższej pracy nowa formuła do obliczania teoretycznej wartości parametru lipofilowości w postaci logPx, która jest oparta na wartościach wybranych indeksów topologicznych, takich jak indeks Balabana (B) i Molekularny Indeks Topologiczny (M) jest ciekawym przykładem zastosowania indeksów opartych na różnych algorytmach obliczeniowych do wyznaczania parametru lipofilowości badanych steroidów.

A Comparative Study of the Lipophilicity of Metformin and Phenformin

The results presented in this paper confirm the beneficial role of an easy-to-use and low-cost thin-layer chromatography (TLC) technique for describing the retention behavior and the experimental lipophilicity parameter of two biguanide derivatives, metformin and phenformin, in both normal-phase (NP) and reversed-phase (RP) TLC systems. The retention parameters (R_F, R_M) obtained under different chromatographic conditions, i.e., various stationary and mobile phases in the NP-TLC and RP-TLC systems, were used to determine the lipophilicity parameter (R_MW) of metformin and phenformin. This study confirms the poor lipophilicity of both metformin and phenformin. It can be stated that the optimization of chromatographic conditions, i.e., the kind of stationary phase and the composition of mobile phase, was needed to obtain the reliable value of the chromatographic lipophilicity parameter (R_MW) in this study. The fewer differences in the R_MW values of both biguanide derivatives were ensured by the RP-TLC system composed of RP2, RP18, and RP18W plates and the mixture composed of methanol, propan-1-ol, and acetonitrile as an organic modifier compared to the NP-TLC analysis. The new calculation procedures for logP of drugs based on topological indices ⁰χ^ν, ⁰χ, ¹χ^ν, M, and M^ν may be a certain alternative to other algorithms as well as the TLC procedure performed under optimized chromatographic conditions. The knowledge of different lipophilicity parameters of the studied biguanides can be useful in the future design of novel and more therapeutically effective metformin and phenformin formulations for antidiabetic and possible anticancer treatment. Moreover, the topological indices presented in this work may be further used in the QSAR study of the examined biguanides.

Application of Thin-Layer Chromatography in Combination with Densitometry for the Determination of Diclofenac in Enteric Coated Tablets

Diclofenac belongs to the drug class non-steroidal anti-inflammatory drugs widely used in Europe as well as all over the world. Thus, it is important to conduct research on its quality control of available pharmaceutical preparations like for example enteric coated tablets. Among various analytical techniques, thin-layer chromatography (TLC) is ideal for this task due to their short time analysis, ease of operation and low cost. Hence, the aim of this study was to develop the optimal conditions of analysis and quantitative determination of diclofenac sodium in enteric tablets by using TLC in combination with densitometry. Of all chromatographic systems tested, the best is the one which consists of silica gel 60F₂₅₄ and cyclohexane: chloroform:methanol:glacial acetic acid (6:3:0.5:0.5 v/v) as the mobile phase, which allows the successful separation of examined diclofenac sodium as active component and the largest number (twelve) of its degradation products as potential impurities of its pharmaceutical products. This indicates that the newly developed method is more effective than previously reported assays by Starek and Krzek. Linearity range was found to be 4.00–18.00 μg/spot for diclofenac sodium. The results of the assay of enteric tablet formulations equals 98.8% of diclofenac sodium in relation to label claim is in a good agreement with pharmaceutical requirements.

The Application of TLC and Densitometry for Quantitative Determination of Meloxicam in Tablets

Background:

Meloxicam is as a non-steroidal anti-inflammatory drug that indicates a strong anti-inflammatory, analgesic and antipyretic activity. It is used in the treatment of osteoarthritis arthritis, osteoarthritis and rheumatoid arthritis in the form of various pharmaceutical preparations.

Objective:

The aim of the work was an elaboration of chromatographic conditions enabling the complete separation of impurities A and B from meloxicam and also its quantitative determination in tablets with use of TLC combined with densitometry as well as the comparison of the method proposed with that described in the literature by Starek and Krzek.

Methods:

The mixture of ethyl acetate: toluene: n-butylamine (2:2:1, v/v/v) was used as a mobile phase. Determination of meloxicam was performed on silica gel and aluminium oxide plates. Chromatographic conditions presented in this work are better than those described by Starek and Krzek.

Results:

Linearity of the method for both types of plates was in the range from 1.0 to 5.0 µg/spot. Limit of quantification for silica gel plates was 0.18 µg/spot, while for aluminium oxide plates it was 0.26 µg/spot. Limit of detection has been also specified, 0.06 μg/spot for silica gel plates and 0.08 μg/spot for aluminium oxide plates. The average amount of meloxicam in tablets obtained on silica gel plates was 100.4%, and on the aluminium oxide plates it was 100.3%.

Conclusion:

The developed method of determination of meloxicam using thin layer chromatography combined with densitometry turned out to be accurate, precise and specific. It can be successfully applied in quality control of meloxicam.

Comparison of the Utility of RP-TLC Technique and Different Computational Methods to Assess the Lipophilicity of Selected Antiparasitic, Antihypertensive, and Anti-inflammatory Drugs

The aim of this study was to assess the lipophilicity of selected antiparasitic, antihypertensive and non-steroidal anti-inflammatory drugs (NSAIDs) by means of reversed phase-thin layer chromatography (RP-TLC) as well by using Soczewiński-Wachtmeister's and J. Ościk's equations. The lipophilicity parameters of all examined compounds obtained under various chromatographic systems (i.e., methanol-water and acetone-water, respectively) and those determined on the basis of Soczewiński-Wachtmeister's and Ościk's equations (i.e., R_MWS and R_MWO) were compared with the theoretical ones (e.g., AlogPs, AClogP, milogP, AlogP, MlogP, XlogP2, XlogP3) and the experimental value of the partition coefficient (logP_exp). It was found that the R_MWS parameter may be a good alternative tool in describing the lipophilic nature of biologically active compounds with a high and low lipophilicity (i.e., antihypertensive and antiparasitic drugs). Meanwhile, the R_MWO was more suitable for compounds with a medium lipophilicity (i.e., non-steroidal anti-inflammatory drugs). The chromatographic parameter _0(a) can be helpful for the prediction of partition coefficients, i.e., AClogP, XlogP3, as well as logP_exp of examined compounds.

Simple and Accurate HPTLC-Densitometric Method for Assay of Nandrolone Decanoate in Pharmaceutical Formulation

This study reports the development and validation of a new, simple, and accurate high-performance thin-layer chromatography (HPTLC)-densitomeric method for the determination of nandrolone decanoate in a commercially available injection formulation. Chromatographic analysis was performed on glass CN modified silica gel 60F₂₅₄ plates developed using n-hexane-ethyl acetate in volume ratio 42.5:7.5 as the mobile phase. Densitometric scanning was carried out at the wavelength of 245 nm. This chromatographic system gave compact spot and a symmetrical peak of nandrolone decanoate with retardation factor (R_F) value at 0.57 (±0.02). The linearity of this method with the high correlation coefficient of calibration plot ranges from 0.780 to 12.500 μg/spot. The developed method is characterized by good precision (coefficient of variation CV < 2%) and high accuracy close to 100.3% (R = 99.0%). Values of limits of detection and quantification equal to 0.231 and 0.700 μg/spot, respectively, confirm the sensitivity of the developed method. The analysis of the pharmaceutical formulation of nandrolone decanoate indicates drug content of 50.5 mg/mL and 101.0% in relation to the label claim. This is in good agreement with the recommendation of the International Council for Harmonisation (ICH) guidelines as well as the pharmacopoeial requirements. The low CV value (<1%) of nandrolone decanoate content in the tested injection formulation confirms the suitability of the proposed HPTLC-densitometric method for routine control of this compound in examined pharmaceuticals.

Influence of Different Chromatographic Conditions on the Level of Detection and Quantitation of Spironolactone by means of TLC-Densitometry

The aim of this study was to estimate the influence of different chromatographic conditions on the limits of detection and limits of quantitation (LODs and LOQs) of spironolactone by means of TLC-densitometry under different chromatographic conditions. A comparison of results obtained showed that the choice of appropriate chromatographic conditions for NP-TLC and RP-TLC analysis with densitometry could effectively decrease the LODs and LOQs of spironolactone. Of all chromatographic systems tested, the best was the one comprising chromatographic plates precoated with a mixture of silica gel 60, kieselguhr F₂₅₄, and mobile phase A (n-hexane-ethyl acetate-glacial acetic acid, 24.5 : 24.5 : 1, v/v/v). The estimated average LOD and LOQ values were 0.034 and 0.103 μg/spot, respectively. This indicates that the described procedure is sufficiently sensitive for the identification and quantification of spironolactone alone. Thereby, the simple and cost-effective TLC-densitometric method can be utilized for the routine quality control of spironolactone in bulk drugs as well as in simple pharmaceutical formulations.

A Simple and Cost-Effective TLC-Densitometric Method for the Quantitative Determination of Acetylsalicylic Acid and Ascorbic Acid in Combined Effervescent Tablets

A new, simple, and cost-effective TLC-densitometric method has been established for the simultaneous quantitative determination of acetylsalicylic acid and ascorbic acid in combined effervescent tablets. Separation was performed on aluminum silica gel 60F254 plates using chloroform-ethanol-glacial acid at a volume ratio of 5:4:0.03 as the mobile phase. UV densitometry was performed in absorbance mode at 200 nm and 268 nm for acetylsalicylic acid and ascorbic acid, respectively. The presented method was validated as per ICH guidelines by specificity, linearity, accuracy, precision, limit of detection, limit of quantification, and robustness. Method validations indicate a good sensitivity with a low value of LOD and LOQ of both examined active substances. The linearity range was found to be 1.50⁻9.00 μg/spot and 1.50⁻13.50 μg/spot for acetylsalicylic and ascorbic acid, respectively. A coefficient of variation that was less than 3% confirms the satisfactory accuracy and precision of the proposed method. The results of the assay of combined tablet formulation equal 97.1% and 101.6% in relation to the label claim that acetylsalicylic acid and ascorbic acid fulfill pharmacopoeial requirements. The developed TLC-densitometric method can be suitable for the routine simultaneous analysis of acetylsalicylic acid and ascorbic acid in combined pharmaceutical formulations. The proposed TLC-densitometry may be an alternative method to the modern high-performance liquid chromatography in the quality control of above-mentioned substances, and it can be applied when HPLC or GC is not affordable in the laboratory.

EVALUATION OF LIPOPHILIC PROPERTIES OF BETAMETHASONE AND RELATED COMPOUNDS

The lipophilicity (R(MW)) of betamethasone and its four related compounds: betamethasone-17,21-dipropionate, betamethasone-17-valerate, betamethasone-21-valerate and also betamethasone disodium phosphate was determined by reversed phase HPTLC and various mobile phase systems (methanol-water, dioxane-water and acetonitrile-water). The chromatographic lipophilicity parameters obtained for all examined compounds using abovementioned mobile phases onto three chromatographic plates (RP-2F254, RP-8F254, RP-18WF254) were compared with the theoretical partition coefficients which have been calculated by different computing programs: AlogPs, AClogP, AlogP, MlogP, KOWWIN, xlogP2, xlogP3, logP(ChemDraw) as well as with logP measured by shake-flask method. The results of this work demonstrate that regardless of applied method the greatest similarity in lipophilic properties show betamethasone-17-valerate, betamethasone-21-valerate and also betamethasone 17,21-dipropionate. The influence of solvent system as mobile phase on R(MW) values of examined compounds was observed. Among different mobile phases (organic modifier-water) proposed in this study, which allowed obtaining the reliable chromatographic lipophilicity parameters for all studied compounds is methanol-water mixture. The performance investigations showed that RP-HPTLC method has proved to be a rapid and cost effective analytical tool for describing the lipophilic properties of betamethasone and its related compounds.

Validation of an RPHPTLC-Densitometric Method Using Silica Gel 60 RP18WF254 for Simultaneous Determination of Nicotinamide in Selected Pharmaceutical Formulations

This research study describes the applicability of silica gel 60 RPW18F254 plates for the development and validation of new, simple, economic, accurate, and precise RPHPTLC-densitometric method suitable for the quantification of nicotinamide (as Vitamin PP) in three marketed preparations. The mobile phase used was methanol-water in volume composition 3 : 7. Detection wavelength was 200 nm. The proposed method was validated according to ICH guidelines and also based on Ferenczi-Fodor and Konieczka reports. Results were found to be linear over a range of 1.00 to 2.00 μg/spot. Limit of detection (LOD) and limit of quantification (LOQ) were 0.15 μg/spot and 0.45 μg/spot, respectively. The percent content of nicotinamide in the investigated preparations was found to be 99.2% (Product 1), 99.3% (Product 2), and 99.4% (Product 3). Developed method is accurate and precise (CV < 3%) and may be successfully applied for the quality control of pharmaceutical formulations containing nicotinamide in the presence of its derivatives, such as N,N-diethylnicotinamide, N-methylnicotinamide, and nicotinic acid.

LIPOPHILICITY ASSESSMENT OF SPIRONOLACTONE BY MEANS OF REVERSED PHASE LIQUID CHROMATOGRAPHY AND BY NEWLY DEVELOPED CALCULATION PROCEDURES

The parameters of lipophilicity of spironolactone (a single member of steroids group), which is widely applied as diuretic and antihypertensive agent, were experimentally determined by reversed-phase TLC and HPLC methods as well as calculated using different computer programs and also by a novel mode based on topological indices. Various stationary phases, such as RP-18WFA4254, RP-2F254, RP-18F254 and also different binary solvent systems composed of organic modifier (e.g., methanol, dioxane, acetone) and water were used as mobile phases in order to predict the following chromatographic parameters: Rm, and logkw, respectively. LogP of examined spironolactone calculated with respective theoretical procedures: AlogPs, logPKOWWIN, xlogP2, xlogP3, AClogP, AlogP, MlogP and also logPaverage were obtained from online package software. The partition coefficients expressed as logP1, logP2 and logP3 were calculated by means of the formulae based on the numerical values of the following topological indices: , 0B, 1B, W, 0χv and IB, which was novelty of this study. A good agreement between logP calculated by new method and experimentally estimated lipophilicity parameters (by chromatography and by shake flask method) was found. The results confirmed applicability of the topological indices for calculating lipophilicity of spironolactone as alternative procedure to the experimental and other computed logP values.

Application of chemometric analysis based on physicochemical and chromatographic data for the differentiation origin of plant protection products containing chlorpyrifos

The aim of this study was to investigate the similarities and dissimilarities between the pesticide samples in form of emulsifiable concentrates (EC) formulation containing chlorpyrifos as active ingredient coming from different sources (i.e., shops and wholesales) and also belonging to various series. The results obtained by the Headspace Gas Chromatography-Mass Spectrometry method and also some selected physicochemical properties of examined pesticides including pH, density, stability, active ingredient and water content in pesticides tested were compared using two chemometric methods. Applicability of simple cluster analysis and also principal component analysis of obtained data in differentiation of examined plant protection products coming from different sources was confirmed. It would be advantageous in the routine control of originality and also in the detection of counterfeit pesticides, respectively, among commercially available pesticides containing chlorpyrifos as an active ingredient.

Application of various methods to determine the lipophilicity parameters of the selected urea pesticides as predictors of their bioaccumulation

Different lipophilicity procedures including a newly developed (based on Ościk's equation) was applied in order to compare various urea pesticides with herbicidal and also insecticidal activity, such as monolinuron, chlorotoluron, diuron, isoproturon, linuron, dimefuron, diflubenzuron, teflubenzuron and lufenuron. Lipophilicity parameters (RMWS and RMW0) of nine examined pesticides were determined on the chromatographic plates RP-8F254 with the use of methanol-water as a mobile phase. Similarity analysis enabled to group all examined pesticides depending on their lipophilic character and allowed to perform a more objective comparison of different lipophilicity parameters obtained for investigated compounds by means of thin-layer chromatography and by the use of computational methods. It was stated that with the number of fluorine in examined pesticides, the lipophilic character of insecticides and also their tendency to bioaccumulation in the living systems increases noticeably. The results of this work confirmed that a new procedure for determining the lipophilicity parameter (RMW0) by Ościk's equation could be a suitable tool in the prediction of pesticide bioaccumulation in living system and may be used as an indicator in design of new urea pesticides, which will be safe for humans and the environment.

Application of selected topological indices to predict retention parameters of selected bile acids separated on modified TLC plates

The aim of this work was to apply some topological indices to predict chromatographic separations of selected bile acids such as: cholic (C), glycocholic (GC), glycodeoxycholic (GDC), chenodeoxycholic (CDC), deoxycholic (DC), lithocholic (LC) and glycolithocholic (GLC). The bile acids were separated on various glass and aluminum TLC plates precoated with silica gel only or with mixture of silica gel and Kieselguhr mixture impregnated with aqueous solution of 1%, 2.5% and 5% of CuSO4, MnSO4, FeSO4 and NiSO4. The mixture of n-hexane - ethyl acetate -acetic acid in various volume compositions was used as a mobile phase. Experimental R(F) and R(M) values obtained on all TLC plates modified with the use of inorganic salts were compared with respective topological indices of studied bile acids. It was suggested that of all indices only index C gives good correlation with chromatographic parameters R(F) and R(M) and can be useful for prediction of chromatographic separations of studied bile acids but only for their optimal separation conditions.

Application of structural descriptors for the evaluation of some physicochemical properties of selected bile acids

Selected bile acids such as: cholic (C), glycocholic (GC), glycodeoxycholic (GDC), chenodeoxycholic (CDC), deoxycholic (DC), lithocholic (LC) and glycolithocholic acids (GLC) were separated by TLC technique. Selected topological indices, based on adjacency and distance matrices, and electrotopological states were calculated for the studied bile acids. Different possibilities of application of structural descriptors to calculate specified physicochemical data of the examined bile acids were found (QSPR). Usability of structural descriptors for the estimation of chromatographic separations of the examined bile acids was shown only for optimal separation conditions. Of all topological indices, only the index C allows to describe the order of adsorption of the examined bile acids (QSRR). Whereas, Gutman's index Mv was proved to be most useful for the estimation of lipophilicity of the examined bile acids (QSAR). The studies indicate that the range of applicability of given structural descriptors is limited for certain analytical and physicochemical problems.