Interaction of humic acid salts with drug preparations

The use of natural polymers that form complexes with drug preparations is promising in the development of drugs of new generation. The possibility of complex formation on the interaction of humic acid salts with papaverine, benzohexonium, and B-group vitamins was demonstrated by calorimetric and potentiometric titration. These interactions can occur between the charged groups of a humic acid macroanion and the positively charged centers of drug molecules. The degree of binding of drug preparations by a natural polymer macromolecule can be determined by the charge and the structure of their molecules.     

The adsorption of bile salts on activated carbon

Activated carbon (AC) has been shown to be effective in reducing serum cholesterol and triglycerides. The mechanism for this action is proposed to be a result of the removal of bile salts in the gut. In this paper, the adsorption of cholate, glycocholate, taurocholate, chenodeoxycholate and deoxycholate on AC is studied in vitro. The results indicate that AC has a high capacity for bile salts, completely removing them from solutions of up to 5 mM and at a rate consistent with physiological activity. Of the 2 types of AC tested, one was shown to exhibit greater capacity and selectivity over the other. A negligible effect was seen with variation of pH through the range 7–9. Desorption occurs in the presence of bile salt-free buffer, but to a minimal extent. Based on these data, the adsorption of bile salts by AC appears to be a likely mechanism for AC-induced reduction of serum lipids.     

Mixed micelles of cationic surfactants and bile acid salts in aqueous media

Critical micelle concentrations of cetyltrimethylammonium-p-toluene sulfonate (CTAT) and cetylpyridinium chloride (CPC) with sodium cholate (NaC) and sodium deoxycholate (NaDC) were determined in aqueous solutions by surface tension measurements. Interaction parameters and mole fraction of the components in mixed micelles were estimated using Rubingh's theory. Strong interaction was observed for each mixed system, a common feature shown by anionic-cationic mixtures. Dramatic effects on the viscosities of these cationic surfactant-bile salt mixtures were seen, and were markedly dependent upon the counterion of the cationic surfactant and the nature of bile salts. Micelles are small and spherical for cationic surfactants in the presence of NaC. Micelle growth was seen for CPC in the presence of NaDC by an increase in viscosity, but a CTAT solution showed an opposite effect on addition of NaDC. Conductance results supported this view. Different behavior of the two bile salts is explained on the basis of their orientation in cationic micelles.     

Different resistance of mammalian red blood cells to hemolysis by bile salts

To evaluate why hemolysis of red blood cells (RBC) by bile acids varies in different mammalian species, we determined the mean corpuscular volume (MCV), lipid content and the concentrations of the conjugates of deoxycholate and of NaCl inducing 50% hemolysis of RBC from healthy humans, pigs, horses, cows, sheep and jaundiced humans. A volume of 0.05 mL of washed RBC at 1% hematocrit, which has the same lipid content but different phospholipid composition and number of erythrocytes (owing to the variable MCV), was incubated in taurodeoxycholate (TDC) solution (0–5 mM) to determine the TDC concentration inducing 50% hemolysis (TDC₅₀). The TDC₅₀ was highest in RBC of sheep and decreased within the series sheep>pig>cow>horse>healthy human>jaundiced human, which have generally increasing MCV. The osmotic resistance followed an inverse order, with jaundiced human >healthy human>horse>cow>pig>sheep. Although we found no correlation between the TDC₅₀ and phospholipid composition of the erythrocytes tested, the extent of bile salt-induced hemolysis seemed to depend on both the MCV and the number of erythrocytes in the incubation medium.     

Effects of bile salts on rat hepatic acyl CoA:Cholesterol acyltransferase

Acyl CoA:cholesterol acyltransferase (EC2.3.1.26, ACAT), responsible for intracellular esterification of cholesterol, may play an important role in cholesterol trafficking within the cell, and thus, in maintenance of cellular cholesterol homeostasis. Bile acids are potential regulators of cholesterol trafficking in the liver. Therefore, the effect of bile salts on hepatic ACAT activity was studied in the perfused rat liver. ACAT activity was increased after liver perfusion with either taurocholate or taurochenodeoxycholate. However, addition of these bile salts at physiological concentrationsin vitro had little effect on microsomal ACAT activity. The increase in hepatic ACAT activity due to perfusion with bile salts was accompanied by reduced accumulation of very low density lipoprotein cholesterol in the perfusate, but there was no effect on 3-hydroxy-3-methylglutaryl-CoA reductase activity. Hepatic ACAT activity was decreased after bile diversion for four hours in the intact animal. This treatment had no statistically significant effect on 3-hydroxy-3-methylglutaryl-CoA reductase activity. These data suggest that bile salts induce changes in hepatic compartmentation and traffic of cholesterol within the hepatocyte accompanied by response of ACAT activity to maintain cellular cholesterol homeostasis.     

Determination of the composition of mixed micelles of bile salts by kinetic dialysis

A kinetic dialysis method for determining the critical micelle concentration and the composition of mixed micelles has been adapted to study a binary system of bile acids. Using kinetic dialysis, the critical micelle concentrations of taurocholate, deoxycholate and taurodeoxycholate were determined. Monomer analysis was performed by colorimetric and radioactive tracer techniques on aliquots of the dialysates. Similarly, the composition of mixed micelles made from various molar fractions of deoxycholate and taurocholate containing tritium and¹⁴C tracers were determined by this method. The results suggest that, for these bile acids, mixed micelle composition is largely predicted by the molar composition of the binary system. Kinetic dialysis has proven to be a rapid procedure and to yield results that agree with critical micelle concentration values previously reported.     

Interaction of polyaniline and transition metal salts: formation of macromolecular complexes

Summary Conditions for complex formation of some transition metal salts and emeraldine base of polyaniline were investigated, and the obtained macromolecular complexes have been characterized by the UV-Vis-IR spectroscopy. It was found that complex formation conditions are dependent on both the cation and anion of the inorganic salt used, as well as on the solvent environment. In some cases, formation of the complex occurred in the form of a precipitate directly in the solution. In other cases, no precipitate was observed in the solution, however, the complex was recognized during film casting from the polyaniline – inorganic salt solution. Electronic absorption spectra for both precipitates and films for the majority of samples possessed features characteristic of the protonated, emeraldine salt form of the polymer. However, IR absorption spectra were different from the protonated polyaniline form. Based on the obtained data, the model of the macromolecular polyaniline – transition metal salt complex is proposed. Received 15 October 2002 / Accepted 5 February 2003 Correspondence to O.P. Dimitriev     

Dietary protein effects on cholelithiasis in hamsters: Interaction with amino acids and bile acids

The objective of this experiment was to study the effects of dietary cottonseed protein and casein on plasma and biliary lipids, plasma amino acids and gallstones in hamsters. Thirty-four male hamsters (60 ± 5 g) were fed either the lithogenic “Dam Diet” (containing 20% casein, 74.3% sucrose and 5.7% vitamin-mineral mix) or a similar diet that contained 20% cottonseed protein for 30 days. Both diets contained protein as a protein isolate. The concentration of alpha-aminobutyric acid was significantly elevated in the casein-fed group. Significant differences in the total plasma cholesterol or lipoprotein cholesterol concentrations were not observed between the two dietary groups. A significant elevation in the absolute concentration of biliary cholesterol was observed in the casein-fed hamsters. Cottonseed protein-fed animals exhibited a significantly elevated concentration of bile acids. The ratio of glycochenodeoxycholic:glycocholic acid was significantly higher in the cotton-seed protein-fed group. This study reports that an elevated concentration of biliary cholesterol with a concomitant decrease in bile acid concentration yields a condition favorable to gallstone formation. It is proposed that cottonseed protein may have a specific effect on the bile acid pool by increasing the ratio of glycochenodeoxycholic acid:glycocholic acid which, in turn, prevents formation of cholesterol gallstones.     

Dietary fibers: V. Binding of bile salts,phospholipids and cholesterol from mixed micelles by bile acid sequestrants and dietary fibers

Mixed micelles were prepared containing combinations of either taurocholate or taurochenodeoxycholate, monoolein, oleic acid, dioleylphosphatidylcholine (lecithin) and cholesterol. These were incubated with commercial bile-acid-sequestering resins, cholestyramine and DEAE-Sephadex, or various dietary fibers and fiber components including wheat bran, cellulose, alfalfa, lignin and 2 viscosity grades of guar gum. Binding was determined as the difference between the radioactivity of each micellar component added and that recovered in the centrifugal supernatant after incubation. In general, the extent of bile salt sequestration was characteristic and reproducible for each bile salt, and was largely unaffected by the presence of one or more additional components of the micellar mixture, including the other bile salt. Cholestyramine bound 81–92% of the bile salts and 86–99% of the phospholipid and cholesterol present in micelles. DEAE-Sephadex sequestered only 49% of the taurocholate and 84% of the taurochenodeoxycholate, but completely removed all of the phospholipid and cholesterol from micelles containing either bile salt. Among the dietary fibers, guar gum of either viscosity bound between 20–38% of each micellar component, whereas lignin, alfalfa, wheat bran and cellulose were progressively less effective in sequestratin of individual components of mixed micelles. The extent of sequestration of micellar components by these resins and fibers is reasonably correlated with the effects of these same materials on lymphatic absorption of lipids and to their suggested hypocholesteremic properties.     

Effects of sodium glycocholate and sodium taurocholate on the mixed micelles of bile salts and nonionic surfactant

Effects of sodium glycocholate (NaGC) and sodium taurocholate (NaTC) on the mixed micelles for two systems consisting of NaGC-octaoxyethylene glycol monon-decyl ether (C₁₀E₈) and NaTC-C₁₀E₈ have been studied as a function of the mixed micelles’ compositions, polarities of the micelles’ interior and mean aggregation numbers. The compositions of the mixed micelles are calculated from critical micelle concentration (CMC) data by using excess thermodynamic quantities. The polarities and mean aggregation numbers are determined from pyrene fluorescence in the mixed micelles. Both mixed systems were nonideal, and the mole fraction of NaGC or NaTC in a mixed micelle near the CMC was less than that in the aqueous mixed solution. However, the mixed micelle of the NaTC-C₁₀E₈ system contained more bile salt molecules than that of the NaGC-C₁₀E₈ system because of a good miscibility of NaTC and C₁₀E₈ molecules. The pyrene fluorescence results suggested that the mixed micelles changed from C₁₀E₈-rich micelles to NaGC- or NaTC-rich micelles, and mean aggregation numbers of the mixed micelles decreased abruptly with increasing mole fraction of bile salts. In the low mole fraction range of bile salts, however, both the polarities and the mean aggregation numbers for the NaTC-C₁₀E₈ system are lower than those for the NaGC-C₁₀E₈ system because of the high mole fraction of NaTC in a mixed micelle, and also because of the different effect of the conjugated group between NaTC and NaGC molecules in the mixed micelles.     

Activation of cellulose with guanidine salts

Conclusions It is possible to reduce the consumption of CS₂ in the xanthation of cellulose to 15% by wt. by preliminarily activating it with guanidine salt solutions in an alkaline medium.Normally filterable viscoses were obtained, fibres from which had satisfactory physicomechanical properties.Translated from Khimickeskie Volokna, No. 3, pp. 56–57, May–June, 1983.     

Properties of aqueous solutions for two binary mixed systems between two kinds of bile salts and nonionic surfactants

The micellar properties of aqueous binary mixed solutions for two systems consisting of sodium cholate (NaC)-octaoxyethylene glycol mono n-decyl ether (C₁₀E₈) and sodium glycocholate (NaGC)-C₁₀E₈ have been studied on the basis of surface tensions, polarity of the micelle interior and the mean aggregation number. Application of two theoretical treatments, based on regular solution and excess thermodynamic quantities for critical micellar concentration (CMC) data from surface tension curves of two mixed systems showed that the mole fraction of each bile salt in the mixed micelles near the CMC is lower than that of the corresponding prepared mole fraction in the mixed solution. The polarity of the interior suggested that the hydrophobicity of intramicelles increased with the increase of the mole fraction of bile salt in the mixed solution and that the mixed micelles become dramatically more hydrophobic at a mole fraction of 0.68 for NaGC−C₁₀E₈ system and 0.75 for NaC−C₁₀E₈ system, respectively. This implies that the micelles become richer in the bile salt molecules and the tendency appears strongly for NaGC−C₁₀E₈ system due to the strong cohesion between the conjugated glycines in the NaGC molecules. The decrease of aggregation number with the increase of the mole fraction of bile salts shows that the micelles approach those of the single system of each bile salt. This supports the previously mentioned facts.     

Studies on N-nitroso bile acid amides in relation to their possible role in gastrointestinal cancer

Cancers of the gastrointestinal tract account for a large proportion of neoplastic diseases which afflict humans. The etiology of gastrointestinal cancer has been attributed in part to exogenous carcinogens, such as food substances and environmental pollutants. Recent hypotheses suggest that carcinogens may arise endogenously. Evidence suggests that some bile acids and their isomeric metabolites may be involved in the pathogenesis of colon cancer. However, the mechanism responsible for their cancer-promoting effect is not clear. We and others propose that one mechanism for the mitogenic effects of bile acids may be N-nitrosation of their glycine and taurine amides; human gastric aspirates do contain small quantities of N-nitroso compounds of other substrates. Many foods contain nitrites and nitrates, which can react with bile acid amides to form N-nitroso derivatives. Our recent studies demonstrated the potential for N-nitroso conjugate formation from ursodeoxycholic acid, a 7β-epimer of chenodeoxycholic acid used as a drug Actigall^® to dissolve gallstones. The N-nitroso derivative of this compound, a direct-acting carcinogen, has a long half-life and, once nitrosated, is stable enough to survive passage through the gastrointestinal tract. We describe the synthesis of N-nitrosated derivatives of various bile acid conjugates and mechanisms of decomposition of (Z)- and (E)-bile acid diazoates. Studies of the effects of enzymes such as cholylglycine hydrolase on the N-nitroso bile acid conjugates and their reaction with DNA are also described. These studies may have important implications in the interplay of diet with endogenous substrates in the etiology of cancers of the stomach, liver, and colon.     

Polymerization of carbazolyl-containing epoxides with triphenylcarbenium salts

Summary Polymerization of 9-(2,3-epoxypropyl) carbazole (EPC) and 1,2-epoxy-6-(9-carbazolyl)-4-oxahexane (ECOH) with triphenylcarbenium hexachloroantimonate and triphenylcarbenium tetrafluoroborate have been studied by the microcalorimetric technique. Triphenylcarbenium salts have turn out to be more efficient catalyst for the polymerization of carbazolyl-containing epoxides than Lewis acids, giving high yields at low initial concentration of the catalyst. Using comparatively restricted conditions of reaction ([triphenylcarbenium saltyda]_o0.02 mol/l t50° C) transition from the conventional active chain end mechanism to the activated monomer mechanism has been observed at a sufficiently high degree of conversion of monomer.     

Electrochemical polymerization of acrylonitrile with quaternary salts

The electrochemical polymerization of acrylonitrile was carried out in the solutions of tetrabutylammonium bromide and tetrabutylphosphonium bromide in N,N-dimethylformamide in a divided electrolytic cell. The formation of polyacrylonitrile of high molecular weight (7.6 × 10⁴) took place in the cathode compartment. The kinetics of the polymerization was investigated for different initial monomer concentrations, current levels, and electrode materials. The polymerization mechanism is anionic.     

Thermal cationic curing with benzylammonium salts

Novel cationic initiators, benzylanilinium salts, were synthesized from benzylchloride and N,N-dimethylaniline followed by exchange of counter anion with SbF₆⁻. Benzylanilinium salts showed thermal latency as initiator in the cationic polymerization of glycidyl phenyl ether. The electrophilic characteristic of the benzyl group of benzylanilinium salts were estimated by the reaction of D₂O using ¹H NMR. The electrophilic characteristics of the benzyl group in benzylanilinium salts depended on the p-substituents (benzyl position in benzylanilinium salts). Cationic curing systems, consisting of benzylanilinium salts and the polymer containing oxirane moieties, were proposed and some properties of films obtained by this systems were evaluated. It was found that cationic curing systems had some better properties, especially resistance to acid, than those of the melamine curing systems and that anilinium salts were more useful than benzylpyridinium salts as the initiators for cationic curing systems for coatings.     

In vitro behavior of marine lipid-based liposomes. Influence of pH, temperature, bile salts, and phospholipase A2

To deliver polyunsaturated fatty acids (PUFA) by the oral route, liposomes based on a natural mixture of marine lipids were prepared by filtration and characterized in media that mimic gastrointestinal fluids. First the influence of large pH variations from 1.5–2.5 (stomach) to 7.4 (intestine) at the physiological temperature (37°C) was investigated. Acidification of liposome suspensions induced instantaneous vesicle aggregation, which was partially reversible when the external medium was further neutralized. Simultaneously, complex morphological bilayer rearrangements occurred, leading to the formation of small aggregates. These pH- and temperature-dependent structural changes were interpreted in terms of osmotic shock and lipid chemical alterations, i.e., oxidation and hydrolysis, especially in the first hours of storage. Besides, oxidative stability was closely related to the state of liposome aggregation and the supramolecular organization (vesicles or mixed micelles). The effects of bile salts and phospholipase A₂ (PLA₂) on the liposome structures were also studied. Membrane solubilization by bile salts was favored by preliminary liposome incubation in acid conditions. PLA₂ showed a better activity on liposome structures than on the corresponding mixed lipid-bile salt micelles. As a whole, in spite of slight morphological modifications, vesicle structures were preserved after an acid stress and no lipid oxidation products were detected during the first 5 h of incubation. Thus, marine lipids constituted an attractive material for the development of liposomes as potential oral PUFA supplements.     

Interaction of mucopolysaccharides with chymotrypsin

Chondroitin sulphates A, B and C form complexes with chymotrypsin which enhance the hydrolytic activity of the enzyme towards glutaryl-l-phenylalanine-p-nitroanilide as much as 270%, as in the case of chondroitin sulphate A. Hyaluronic acid, a non-sulphated mucopolysaccharide, at a weight ratio of 6.67:1 to the enzyme, does not influence the rate of cleavage of the substrate by chymotrypsin. Proflavin difference spectra and ultra-violet spectra suggest that a complex is formed between chymotrypsin and hyaluronic acid, as well as chondroitin sulphates A, B and C. The proflavin molecule is not displaced from the active site of the enzyme upon association with the mucopolysaccharides. When the mucopolysaccharide—chymotrypsin complexes are electrophoresed on analytical polyacrylamide disc gels at pH 8.9, the complexes are visualized by toluidine blue (for mucopolysaccharide), coomassie brilliant blue (for protein) and by the zymogram technique (with glutaryl-l-phenylalanine-β-naphthylamide), at a position between that for chymotrypsin alone and that for the mucopolysaccharide alone.