Estimation of chromatographic lipophilicity of bile acids and their derivatives by reversed-phase thin layer chromatography.

The main goal of this study was to estimate the lipophilicity and investigate the molecular mechanism of retention of bile acids and their derivatives in order to find an objective manner of quantitative comparison of different chemically bonded stationary phases for high performance TLC in terms of their (dis)similarities. Highly significant correlations were obtained between different experimental indices of lipophilicity (R(M0), S and the scores corresponding to the first principal component) estimated on CN(F254s) and RP-18(F254s) and some computed log P values that combine electronic and topological aspects. The most statistically significant quantitative structure-property relationship models, using descriptors from Dragon software, multiple linear regression and genetic algorithm, were also obtained in the case of CN(F254s) and RP-18(F254s) stationary phases. Cross-validation suggests a good reliability of the results. The contribution of 2D and 3D descriptors, which are related to atomic mass, together with reactivity parameters such as polarizability and electronegativity seem to control the chromatographic mechanism (lipophilicity) on all stationary phases.

Hydrophobicity and haemolytic potential of oxo derivatives of cholic, deoxycholic and chenodeoxycholic acids.

The objective of this work was to study the effect of structure of bile acids on their membranolytic potential and extent of overlapping of the information about the membranolytic potential of bile acids and their physico-chemical parameters, namely: retention index R(M0) (as a measure of bile acid hydrophobicity, reversed-phase thin-layer chromatography (RPTLC)), lecithin solubilisation (measure of the interaction of bile acids with phospholipids) and critical micellar concentration (CMC). It was found that bile acid concentrations at 100% lysis of erythrocyte membranes is described best by their CMC values, whereas at 50% lysis the parameter used is lecithin solubilisation. This indicates that different mixed micelles are formed in the membrane lysis at lower and higher concentrations of bile acids. Replacement of the hydroxyl (OH) group in the bile acid molecule with an oxo group yields derivatives with lowered hydrophobicity, power of lecithin solubilisation, tendency for self-aggregation as well as the membranolytic activity.

Influence of sodium monoketocholate on the hypolipidemic activity of lovastatin in healthy and diabetic rats.

Recent findings regarding the physiological transport mechanisms and metabolism of bile acids have led to an increased interest in their synthetic derivatives, especially as transmucous transporters. The aim of this study was to examine the influence of the synthetic sodium salt of monoketocholic acid (Na-MKHA) on the hypolipidemic activity of lovastatin. The effects of a 7 days administration of lovastatin (20 mg/kg b.w.) (experimental group 1, n=5) and a combination of lovastatin (20 mg/kg b.w.) and Na-MKHA (2 mg/kg b.w.) (experimental group 2, n=5) in group of healthy and diabetic male Wistar rats were investigated. The animals in the control group of healthy (n=5) and diabetic (n=5) rats were treated with physiological saline (10 ml/kg b.w.) per os twice a day. In the healthy rats, lovastatin increased the low density lipoprotein (LDL) (32.14%) and non-high density lipoprotein (HDL) (15.38%) cholesterol and decreased HDL cholesterol levels (9.89%), and also increased the investigated atherogenic ratios. Na-MKHA significantly potentiated lovastatin activity, and its effects on the LDL (p<0.05; 102.70%), HDL (p<0.01; 32.93%) and non-HDL (p<0.05; 65%) cholesterol levels, as well as the LDL/HDL (p<0.02; 231.11%), total cholesterol/HDL (p<0.02; 70.52%) and non-HDU/HDL cholesterol ratios (p<0.02; 167.12%). In diabetic animals, the potentiating effect of Na-MKHA was not significant. The stimulatory effect of Na-MKHA is probably a consequence of the intensified transmembrane transport of lovastatin due to the direct action of bile acids on the cell membranes, as well as a result of their enhanced transport via specific bile acid transport systems.

Modeling and prediction (correction) of partition coefficients of bile acids and their derivatives by multivariate regression methods.

Different multiple regression methods including forward stepwise multiple linear regression (MLR), principal component regression (PCR) and partial least squares (PLS) have been applied to the modeling of partition coefficient (lipophilicity) of bile acids and their derivatives by means of 16 different descriptors obtained by using Alchemy package software and retention index R(Mo) as an experimental estimation of lipophilicity. Retention indices for bile acids and their derivatives were determined by reversed phase high-performance thin layer chromatography on RP-18 W bounded stationary phase with methanol-water in different volume proportions as mobile phase. The results achieved concerning the prediction of Log P are highly significant and consistent with the molecular structure of the compounds investigated. The sum of absolute values of the charges on each atom of the molecule, in electrons (SQ), the sum of absolute values of the charges on the nitrogens and oxygens in the molecule, in electrons (SQ(NO)), specific polarizability of a molecule (SP), the third-order connectivity index ((3)chi) and molecular lipophilicity, seem to be dominant in the partition mechanism. In addition, regression models developed have allowed a correct estimation of the partition coefficients of cholic acid (Log P(HA)=2.93; Log P(A)(-)=2.02) as compared with reported experimental values (Log P(HA)=2.02; Log P(A)(-)=1.1).

Formation of hydrogen-bonded complexes between bile acids and lidocaine in the lidocaine transfer from an aqueous phase to chloroform.

Bile acids are amphiphilic molecules, which, in addition to their physiological role, have also acquired increasingly more important pharmacological applications. It has been shown that these compounds have a promoting effect on the transport of many drugs through the cell membrane. Pharmacodynamic studies showed that they exerted a significant effect on the analgesic action of lidocaine. This study is concerned with the determination of the constants of hydrogen-bonded complexes formed between the investigated bile acids and lidocaine. It was found that a prerequisite for forming such a complex is the existence of at least two OH groups or one OH group and one keto group in the bile acid molecule at an appropriate mutual distance. If a keto group is involved in lidocaine binding, the resulting complex has a larger equilibrium constant. A model--multiple linear regression equation--was constructed, relating the molecular descriptors to the equilibrium constant of hydrogen-bonded complex. It was also shown how the complex formed between lidocaine and bile acid influences the rate constant of the decrease of lidocaine concentration in the aqueous phase during its transfer to the chloroform solution of a bile acid. It was found that the complex formed between lidocaine and bile acids plays an important role in the appearance of the depot effect of lidocaine.

Effect of stevioside and sodium salt of monoketocholic acid on glycemia in normoglycemic and diabetic rats.

This study investigated the effect of a commercial preparation of stevioside and a synthetic compound, sodium salt of monketocholic acid (MKC), administered per os (p.o.) and also adminstered via an osmotic pump, on glycemia in normoglycemic and diabetic Wistar rats. Diabetes was induced with alloxan, 100 mg/kg, i.p. Normoglycemic and diabetic rats were treated p.o. for five days either with physiological solution (1 ml/kg, controls), stevioside (20 mg/kg), MKC (4 mg/kg) and a combination of stevioside (20 mg/kg) and MKC (4 mg/kg). Apart from p.o. adminstration, stevioside and MKC were also administered via a subcutaneously (s.c.) implanted osmotic pump. During treatment and upon termination of the latter, glycemia was measured and the rats that were treated p.o. were subjected to the oral glucose tolerance test (OGTTT) at a dose of 1 g/kg. Following this animals were anesthetized with urethane (0.75 g/kg, i.p.) and killed by cardiopunction to determine C-peptide levels in the serum. In all three groups of normoglycemic rats highest decrease in glucose levels was observed on the fourth day of the experiment. The stevioside + MKC combination showed a stronger hypoglycemic effect compared to individual treatments with stevioside and MKC (3.73:4.80:4.73 mmol/L). In the group of diabetic rats that received both substances via the osmotic pump, the hypoglycemic action was also stronger compared to the individual treatments with stevioside and MKC (16.15:18.89:18.75 mmol/L). The treatment of healthy rats with both substances p.o. caused no statistically significant difference in glycemia, whereas in diabetic rats the combination of stevioside + MKC showed a statistically significant decrease in glycemia compared to control values. In both groups of rats, treatment with stevioside and MKC and their combination prevented an increase in glucose concentrations in the OGTT. Only the administration of stevioside by osmotic pump yielded a statistically significant increase in the concentrations of C-peptide in the serum of healthy rats. Compared to controls, the concentrations of C-peptide in diabetic rats were significantly higher after treatment with either stevioside or its combination with MKC, irrespective of the mode of administration.

Critical micellar concentrations of keto derivatives of selected bile acids: thermodynamic functions of micelle formation.

The knowledge of the process of formation of molecular aggregates of bile acids in aqueous media and of the corresponding critical micellar concentrations (CMCs) is of great significance because of the biological importance of these compounds and their pharmacological applications. In view of this, the present study is concerned with the determination of CMCs of cholic and chenodeoxycholic acids and their keto derivatives at different temperatures with the aim to calculate the standard thermodynamic functions of micelle formation. Based on the molecular descriptors for tested compounds and entropy of micelle formation, the method of principal component analysis (PCA) allowed grouping of the behavior of tested molecules at 30, 50 and 70 degrees C. To one group belong cholic acid and its keto derivatives, the other group consisting of chenodeoxycholic and deoxycholic acids and their keto derivatives. For each group, the derived multiple linear regression equations of the entropy dependence on temperature contains different independent variables. A main difference between the two groups of tested bile acids is in the energy of dipole-dipole interaction, which appears to be temperature dependent, and in the case of the latter group comes into play as an independent variable already in the regression equation derived for 30 degrees C. The most remarkable changes of the descriptors with temperature were observed in the group of cholic acid and its derivatives.

Effect of cholic acid and its keto derivatives on the analgesic action of lidocaine and associated biochemical parameters in rats.

This study examined the effect of the structure and concentration of cholic acid and its keto derivatives on the local analgesic action of lidocaine in rats, measured by an analgesimetric method. The increase in bile acid concentrations in the administered lidocaine solution increased the duration of local anesthesia. It was found that the introduction of keto groups into the cholic acid molecule yielded derivatives with lower promotory action, i.e. decreased the duration of local anesthesia. The biochemical parameters investigated indicated that the keto derivatives of cholic acid exhibited no toxicity compared to that of cholic acid itself.

Determination of critical micellar concentrations of cholic acid and its keto derivatives.

The critical micellar concentration (CMC) values of keto derivatives of cholic acid (3alpha,12alpha-dihydroxy-7-oxo-5beta-cholanoic acid, 3alpha,7alpha-dihydroxy-12-oxo-5beta-cholanoic acid, 12alpha-hydroxy-3,7-dioxo-5beta-cholanoic acid, 3alpha-hydroxy-7,12-dioxo-5beta-cholanoic acid, 3,7,12-triketo-5beta-cholanoic acid) and cholic acid itself, were determined. Replacement of hydroxyl groups in cholic acid molecule with keto groups yields the derivatives whose CMC values increase with increase in the number of keto groups introduced. The CMCs of derivatives with the same number of keto groups but at different positions do not differ significantly. The relationship between the number of keto groups in the molecule of cholic acid keto derivatives and CMC value can be described by the following equation: CMC=43 number of keto groups+14.667. The effect of NaCl concentration on CMC increases with increase in the number of keto groups.

3Alpha,7alpha-dihydroxy-12-oxo-5beta-cholanate as blood-brain barrier permeator.

The aim of the study was to test the efficacy of 3alpha,7alpha-dihydroxy-12-oxo-5beta-cholanate as a blood-brain barrier (BBB) permeator by examining its effect on quinine uptake into the central nervous system in rats, analgesic action of morphine, and on the sleeping time induced by pentobarbital. The obtained results indicate that sodium 3alpha,7alpha-dihydroxy-12-oxo-5beta-cholanate can be considered as modifier of BBB permeability, as it exhibited a promoting effect in all three tests. In the test of quinine uptake, methyl ester of 3alpha,7alpha-dihydroxy-12-oxo-5beta-cholanoic acid (included in the study for comparison) did not show a promoting effect, which can suggest its specific action.

[Current aspects in pharmacologic use of bile acids]. / Savremeni pravci farmakoloske primene zucnih kiselina.

EFFECTS OF BILE ACIDS AND THEIR SALTS ON ABSORPTION OF OTHER SUBSTANCES: Bile acids and their salts increase intestinal absorption of lipids and transmembrane and paracellular transfer of small and endogenous and exogenous polar molecules. It has been established that they are good promotors of insulin absorption through skin and nasal mucose, and of blood-brain barrier transfer of salycilates and quinine. EFFECTS OF BILE ACIDS AND THEIR SALTS ON ABSORPTION OF OTHER SUBSTANCES AND THEIR POTENTIAL ACTION: It has been established that combination of bile acids with amphotericin B has potential Leishmanicideal effect and combination with ciprofloxacine has improved its antibacterial activity against Pseudomonas aeruginosa in vitro. BILE ACIDS: PHARMACADYNAMIC EFFECTS: Bile acids have analgesic and hypoglycemic effect. They also have anti-HIV effect probably suppressing virus transmission from cell to cell. CONCLUSION: New studies of natural bile acids and new synthetic bile acids have revealed that they are not only adjuvants to existing active principles in pharmaceutical forms, but they can act as new therapeutic agents. However, it is necessary to study their possible mechanisms, but they are not crucial for their therapeutic application. Toxicological and pharmacological studies will determine the role of newly synthesized bile acids and their salts in current therapy.