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PubMed1976

C26-Analogs of naturally occurring C27 bile alcohols.

C26 Bile of the 24-nor-5beta-cholestane series were prepared starting from methyl cholate. A Grignard reaction of methyl magnesium iodide with methyl cholate yielded 24-nor-5beta-cholestane-3alpha, 7alpha, 12alpha, 25-tetrol which was dehydrated TO FORM a mixture of 24-nor-5beta-cholest-23-ene-3alpha, 7alpha, 12 alpha-triol and the corresponding delta25 compound. Oxidation of the former with OsO4 yielded 24-nor-5beta-cholestane-3alpha, 7alpha, 12alpha, 23epsilon, 25pentol, while catalytic hydrogenation of a mixture of the delta23 and delta25 triols resulted in the formation of 24-nor-5beta-cholestane-3-alpha-, 7alpha-12alpha-triol. The structures of these new compounds were confirmed by infrared and nuclear megnetic resonance spectrometry and by gas-liquid chromatography-mass spectrometry.

Chromatography, Gas↗
PubMed2001

Determination of synthesized alpha-vitamin E by micellar electrokinetic chromatography.

We developed a micellar electrokinetic chromatography method (MEKC) for the direct determination of the content of synthesized alpha-vitamin E. It was found that under the optimum separation conditions 7 mM borate + 14 mM phosphate + 15 mM sodium dodecyl sulfate (SDS) + 10 mM sodium cholate (NaCh) + 8% acetonitrile (pH 9.2) with UV detection wavelength at 214 nm, 16 kV constant voltage, and 26 degrees C constant temperature, alpha-vitamin E and its isomers can be baseline separated and alpha-vitamin E was quantitatively analyzed. In addition, the sample recovery, the limit of detection and the repeatability of the method were investigated. The influence of various parameters on the separation such as SDS concentration, NaCh concentration, buffer pH and acetonitrile percentage were also discussed.

Acetonitriles↗
PubMed2001

Stacking and separation of coproporphyrin isomers by acetonitrile-salt mixtures in micellar electrokinetic chromatography.

The effectiveness of the addition of salt and acetonitrile in the sample matrix to induce narrowing of the analyte zones is demonstrated for the first time in micellar electrokinetic chromatography (MEKC). Using coproporphyrin (CP) I and III isomers as test compounds, the use of sodium cholate (SC) as the micelle in the separation buffer and a high concentration of sodium chloride in the aqueous sample solution (without the presence of an organic solvent) were found to provide enhancement in peak heights for both CP I and III, but yielded very poor resolution of these two positional isomers at sample size of 10% capillary volume or larger. With the addition of acetonitrile as the organic solvent in the aqueous sample solution (acetonitrile-salt mixtures), baseline/partial resolution of CP I and III was obtained even at large injection volumes, along with significant increase in peak heights for both isomers. Possible mechanisms responsible for the narrowing of analyte zones are briefly discussed. The effects of experimental parameters, such as concentrations of salt and acetonitrile, on peak heights and resolution of the test compounds were studied. Importantly, the usefulness of the present method was demonstrated for the MEKC determination of endogenous CP I and III present in normal urine samples with good separation and detection performances.

Acetonitriles↗
PubMed2005

Non-aqueous capillary electrophoresis for separation and simultaneous determination of fraxin, esculin and esculetin in Cortex fraxini and its medicinal preparations.

A non-aqueous capillary electrophoresis method has been developed for the separation and simultaneous determination of fraxin, esculin and esculetin in Cortex fraxini and its preparation for the first time. Optimum separation of the analytes was obtained on a 47 cm x 75 microm i.d. fused-silica capillary using a non-aqueous buffer system of 60 mM sodium cholate, 20 mM ammonium acetate, 20% acetonitrile and 3% acetic acid at 20 kV and 292 K, respectively. The relative standard deviations (RSDs) of the migration times and the peak heights of the three analytes were in the range of 0.23-0.28 and 2.12-2.60%, respectively. Detection limits of fraxin, esculin and esculetin were 0.1557, 0.4073 and 0.5382 microg/mL, respectively. In the tested concentration range, good linear relationships (correlation coefficients 0.9995 for fraxin, 0.9999 for esculin and 0.9992 for esculetin) between peak heights and concentrations of the analytes were observed. This method has been successfully applied to simultaneous determination of the three bioactive components with the recoveries from 90.2 to 109.2% in the five samples.

Acetates↗
PubMedDate not supplied

Characterization and modulation by drugs of sheep liver microsomal flavin monooxygenase activity.

The flavin monooxygenases (FMO) catalyse the NADPH and oxygen-dependent oxidation of a wide range of nucleophilic nitrogen-, sulfur-, phosphorus-, and selenium heteroatom-containing chemicals, drugs, and agricultural agents. In the present study, sheep liver microsomal FMO activity was determined by measuring the S-oxidation rate of methimazole and the average specific activity obtained from different microsomal preparations was found to be 3.8 +/- 1.5 nmol methimazole oxidized min(-1) mg(-1) microsomal protein (mean +/- SE, n = 7). The presence of 0.1% Triton X-100 in the reaction mixture caused an increase of specific sheep liver microsomal FMO activity towards methimazole to 6.1 +/- 1.4 nmol methimazole oxidized min(-1) mg(-1) microsomal protein (mean +/- SE, n = 6). Metabolism of imipramine and chlorpromazine was measured by following the oxidation of cofactor NADPH spectrophotometrically at 340 nm. Sheep liver microsomal FMO activity towards imipramine and chlorpromazine was found to be 10.7 and 12.3 nmol NADPH oxidized min(-1) mg(-1) microsomal protein, respectively. Characterization of sheep liver enzyme was carried out using methimazole as substrate and the maximum FMO enzyme activity was detected at 37 degrees C and at pH 8.0. The apparent K(m) value of sheep liver microsomal FMO for methimazole was 0.118 mM. Effects of the detergents Triton X-100, Cholate, and Emulgen 913, on FMO activity were determined and FMO activity was found to increase with the addition of detergents to the reaction medium. Sheep liver microsomal FMO-catalysed methimazole oxidation was inhibited by imipramine and chlorpromazine when these drugs were used at high concentrations. Western blot-immunochemical analysis revealed the presence of FMO3 in sheep liver microsomes.

Animals↗
PubMed2003

Separation of some chiral flavanones by micellar electrokinetic chromatography.

Micellar electrokinetic chromatography (MEKC) was applied for enantioseparation of selected flavanones, including naringin, hesperidin, neohesperidin, naringenin, hesperetin, pinostrobin, isosakuranetin, eriodictyol, and homoeriodictyol. gamma-Cyclodextrin (gamma-CD) and sodium cholate (SCh) were used as chiral modifiers inducing enantioselectivity to the background electrolyte. From among many investigated selectors only these two appeared to possess the best enantioselective properties in respect to studied flavanones. The mechanisms of their action are a little different; SCh used above critical micelle point concentration forms chiral micelles itself while gamma-CD is deprived of this property and requires addition of surfactants as, e.g., sodium dodecyl sulfate. It was found that SCh enables separation of flavanone glycosides diastereomers while separation of enantiomers of flavanone aglycones may be achieved with gamma-CD. Consideration of structural relation led to the suggestion that interaction of sugar moiety of glycosides with SCh micelles give rise to chiral recognition. MEKC appeared to be a suitable and efficient analytical tool to follow enantiomeric composition of flavanones.

Chromatography, Micellar Electrokinetic Capillary↗
PubMed2003

Stacking and separation of enantiomers by acetonitrile-salt mixtures in micellar electrokinetic chromatography.

The feasibility of employing the "acetonitrile stacking" method in micellar electrokinetic chromatography (MEKC) for the on-line preconcentration and separation of enantiomers is demonstrated for the first time. The effects of various experimental parameters on the stacking and separation of three different pairs of optical isomers, i.e., two substituted naphthyl enantiomers and one dansylated-DL-amino acid, were examined. In particular, the effectiveness of the addition of acetonitrile and salt in the sample matrix to induce narrowing of the analyte bands was investigated in the presence of sodium cholate as the chiral surfactant micelle in the separation buffer. For example, it was found that the presence of both acetonitrile and 1% NaCl in the sample matrix (volume ratio = 2:1) led to a significant improvement of the peak height and resolution for the MEKC separation of a pair of R(-)/S(+)-1,1'-binaphthyl diyl hydrogen phosphate enantiomers when the injection sample size was relatively large (e.g., 12% capillary volume). Furthermore, the feasibility of combining salting-out solvent extraction (off-line) and acetonitrile stacking (on-line) as a novel approach for sample preconcentration in capillary electrophoresis was also demonstrated.

Acetonitriles↗
PubMedDate not supplied

Separation of bisbenzylisoquinoline alkaloids by micellar electrokinetic chromatography.

The micellar electrokinetic chromatographic (MEKC) separation of seven bisbenzylisoquinoline alkaloids has been developed. The effects of various separating factors were studied. Optimum separation was achieved using a buffer (pH 9.2) of 20 mM sodium borate and 20 mM sodium dihydrogen phosphate buffer containing 55 mM sodium cholate; the optimum voltage and injection time were 21 kV and 0.05 min, respectively. Highest peak efficiency was obtained when the analytes were dissolved in 10 mM sodium dodecyl sulphate as sample matrix for injection. The elution order of the bisbenzylisoquinoline alkaloids was related to their lipophilicity. The resolution, run time and detection limits of the MEKC method were compared with those of an HPLC method developed previously.

Alkaloids↗
PubMed2000

Quantitative determination of zwitterionic detergents using salt-induced phase separation of Triton X-100.

Zwitterionic detergents interfere with the salt-induced phase separation for nonionic detergents in a concentration-dependent manner by shifting the normal cloud point of nonionic detergents to a higher ionic strength at room temperature. This phenomenon was used to determine the concentration of the zwitterionic detergents CHAPS, CHAPSO, and sulfobetaine SB-12 in solution by titration with ammonium sulfate in the presence of Triton X-100. Among the ionic detergents tested, the method was only applicable to sodium cholate. The assay can be used to control the removal of zwitterionic detergents during the reconstitution of membrane proteins in liposomes. However, it cannot be used to determine the specific binding of zwitterionic detergents to highly diluted, pure membrane proteins because of the limited sensitivity. Neither proteins nor phospholipids interfered with this method at concentrations up to 20 mg/ml of test solution (human serum albumin) or 10 mg/ml (phospholipids), respectively. Since the assay is based on the competition between salts and nonionic detergents for water molecules, it is important to equalize the ionic strength of samples and calibration standards.

Cholic Acids↗
PubMed2002

The function of OmpA in Escherichia coli.

Outer membrane protein A (OmpA) is a major protein in the Escherichia coli outer membrane. In this study, the function of OmpA in E. coli stress survival was examined. An E. coli K1 ompA-deletion mutant was significantly more sensitive than that of its parent strain to sodium dodecyl sulfate (SDS), cholate, acidic environment, high osmolarity, and pooled human serum. A number of amino acid changes at the extracellular loops of OmpA did not affect the viability of E. coli, while short peptide insertions in the periplasmic turns of the OmpA beta-barrel decreased E. coli resistance to environmental stresses. Moreover, ompA mutants were found to survive much better within brain microvascular endothelial cells than the wild-type strain, supporting that OmpA is a major target in mammalian host cell defense. These results indicated that OmpA plays a vital structural role in E. coli, and suggested that a perfect beta-barrel structure of OmpA is important for outer membrane stability. Based on these results and the published OmpA structural analyses, I propose that OmpA is composed of three functional domains including a hydrophilic extracellular mass, a beta-barrel transmembrane structure, and a peptidoglycan binding domain.

Amino Acid Sequence↗
PubMed2005

The roles of Kupffer cells in hepatic dysfunction induced by ischemia/reperfusion in rats.

This study examined the role of Kupffer cells in altering the hepatic secretory and microsomal function during ischemia and reperfusion (Is/Rp). Rats were subjected to 60 min of hepatic ischemia, followed by 1 and 5 h of reperfusion. Gadolinium chloride (GdCl3, 7.5 mg/kg body weight, intravenously) was used to inactivate the Kupffer cells 1 day prior to ischemia. Is/Rp markedly increased the serum aminotransferase level and the extent of lipid peroxidation. GdCl3 significantly attenuated these increases. Is/Rp markedly decreased the bile flow and cholate output, and GdCl3 restored their secretion. The cytochrome P450 content was decreased by Is/Rp. However, these decreases were not prevented by GdCl3. The aminopyrine N-demethylase activity was decreased by Is/Rp, while the aniline p-hydroxylase activity was increased. GdCl3 prevented the increase in the aniline p-hydroxylase activity. Overall, Is/Rp diminishes the hepatic secretory and microsomal drug-metabolizing functions, and Kupffer cells are involved in this hepatobiliary dysfunction.

Alanine Transaminase↗
PubMed2004

A cholesterol biosynthesis inhibitor from Rhizopus oryzae.

A bile acid derivative, methyl cholate (1), was isolated from EtOAc extract of the fungus Rhizopus oryzae as a cholesterol biosynthesis inhibitor. It showed moderate inhibitory activity on cholesterol biosynthesis in human Chang liver cells. Compound 1 exhibited inhibitory effect on the later step of cholesterol biosynthesis, indicating that its action mode is different from that of statins that act on the HMG-CoA reductase.

Anticholesteremic Agents↗
PubMed2000

Purification, characterization, and molecular cloning of group I phospholipases A2 from the gills of the red sea bream, Pagrus major.

Phospholipase A2 (PLA2) activity was investigated in various tissues of male and female red sea bream. In both male and female fishes, the specific activity of PLA2 in the gills was 70 times higher than that in other tissues, such as the adipose tissue, intestine, and hepatopancreas. Therefore, we tried to purify PLA2 from the gill filaments of red sea bream to near homogeneity by sequential chromatography on Q-Sepharose Fast Flow, Butyl-Cellulofine, and DEAE-Sepharose Fast Flow columns, and by reversed-phase high-performance liquid chromatography. Two minor and one major PLA2, tentatively named G-1, G-2 and G-3 PLA2, were purified, and all showed a single band with an apparent molecular mass of approximately 15 kDa by sodium dodecylsulfate-polyacrylamide gel electrophoresis. The exact molecular mass values of G-1, G-2, and G-3 PLA2 were 14,040, 14,040 and 14,005 Da, respectively. G-1, G-2, and G-3 PLA2 had a Cys 11 and were all identical in N-terminal amino acid sequences from Ala-1 to Glu-56. A full-length cDNA encoding G-3 PLA2 was cloned by reverse transcriptase-polymerase chain reaction and rapid amplification of cDNA ends methods, and G-3 PLA2 was found to be classified to group IB PLA2 from the deduced amino acid sequence. G-1, G-2, and G-3 PLA2 had a pH optimum in an alkaline region at around pH 9-10 and required Ca2+ essentially for enzyme activity, using a mixed-micellar phosphatidylcholine substrate with sodium cholate. These results demonstrate that three group I PLA2, G-1, G-2, and G-3 PLA2, are expressed in the gill filaments of red sea bream.

Adipose Tissue↗
PubMed1995

Synthesis of 3 alpha, 7 alpha, 12 alpha-trihydroxy- and 3 alpha, 7 alpha-dihydroxy-5 beta-cholestan-26-oic acids by the use of beta-ketosulfoxide.

The biosynthetic intermediates of bile acid, 3 alpha, 7 alpha, 12 alpha-trihydroxy- and 3 alpha, 7 alpha-dihydroxy-5 beta-cholestan-26-oic acids, were synthesized by means of the thermal elimination of beta-ketosulfoxides. The alpha, beta-unsaturated ketones as key compounds of the synthesis, 3 alpha, 7 alpha, 12 alpha-trihydroxy- and 3 alpha, 7 alpha-dihydroxy-5 beta-cholest-25-en-24-ones, were effectively derived from the beta-ketosulfoxides prepared from methyl cholate or chenodeoxycholate by reaction with methylsulfinylcarbanion. These unsaturated ketones were converted into 3 alpha, 7 alpha, 12 alpha, 26-tetrahydroxy- and 3 alpha, 7 alpha, 26-trihydroxy-5 beta-cholestanes by reductive deoxygenation and hydroboration, of which stereoisomers were chromatographically separated into 25S- and 25R- isomers. The oxidation of each of the above isomeric alcohols after the protection of the hydroxyl groups on the steroidal ring and the following hydrolysis gave the title 26-carboxylic acids.

Chenodeoxycholic Acid↗
PubMed1990

Miniaturization of a liquid membrane sensor for the determination of bile acids.

The preparation of a compound liquid ion exchanger used for the miniaturization of bile acid sensitive microelectrode is described. The liquid ion exchanger is 2% benzyldimethylhexadecylammonium cholate in decanol/0.1 M hexadecyltributylammonium taurocholate in 5% hexachlorobenzene, 0.5% bromoacetanilide O-dichlorobenzene. The slopes, detection limits, selectivity coefficients, drifts and response time of the various bile acid sensitive microelectrodes are evaluated and compared.

Bile Acids and Salts↗
PubMed2004

Noninvasive methods to determine the critical micelle concentration of some bile acid salts.

In this work the critical micelle concentrations (cmc) of four bile salts, sodium cholate, sodium glycocholate, sodium deoxycholate, and sodium glycodeoxycholate, are determined and presented. Three independent noninvasive methodologies (potentiometry, derivative spectrophotometry, and light scattering) were used for cmc determination, at 25 degrees C with ionic strength adjusted to 0.10 M with NaCl. Spectrophotometric and potentiometric studies of some bile salts were also executed at various ionic strength values, thus allowing the influence of the ionic strength on the cmc value of the bile salt to be assessed. A critical comparison of the cmc values obtained with data collected from the literature is presented. Furthermore, this work makes an evaluation of the conceptual bases of different methodologies commonly used for cmc determination, since variations in the results obtained can be related mainly to different intrinsic features of the methods used (such as sensitivity or the need to include tracers or probes) or to the operational cmc definition applied. The undoubted definition of the experimental bile salt concentration that corresponds to cmc (operational cmc) is essential since in the case of these amphiphiles the formation of micelles is not as abrupt as in the case of ordinary association colloids. The biphasic nature of their aggregation leads to a "round-shaped" variation of the experimental parameters under analysis, which makes difficult the evaluation of the cmc values and can be responsible for the different results obtained.

Bile Acids and Salts↗
PubMed2003

Micelle formation of sodium chenodeoxycholate and solubilization into the micelles: comparison with other unconjugated bile salts.

Micellization of sodium chenodeoxycholate (NaCDC) was studied for the critical micelle concentration (CMC), the micelle aggregation number, and the degree of counterion binding to micelle at 288.2, 298.2, 308.2, and 318.2 K. They were compared with those of three other unconjugated bile salts; sodium cholate (NaC), sodium deoxycholate (NaDC), and sodium ursodeoxycholate (NaUDC). The I(1)/I(3) ratio of pyrene fluorescence and the solubility dependence of solution pH were employed to determine the CMC values. As the results, a certain concentration range for the CMC and a stepwise molecular aggregation for micellization were found reasonable. Using a stepwise association model of the bile salt anions, the mean aggregation number (n) of NaCDC micelles was found to increase with the total anion concentration, while the n values decreased with increasing temperature; 9.1, 8.1, 7.4, and 6.3 at 288.2, 298.2, 308.2, and 318.2 K, respectively, at 50 mmol dm(-3). The results from four unconjugated bile salts indicate that the number, location, and orientation of hydroxyl groups in the steroid nucleus are quite important for growth of the micelles. Activity of the counterion (Na(+)) was determined by a sodium ion selective electrode in order to confirm the low counterion binding to micelles. The solubilized amount of cholesterol into the aqueous bile salt solutions increased in the order of NaUDC<NaC<NaCDC<NaDC. The first stepwise association or solubilization constants (K(1)) between a cholesterol monomer and a vacant micelle were evaluated at different bile salt concentrations. The constants were also determined for polycyclic aromatic compounds (benzene, naphthalene, anthracene, and pyrene). The corresponding DeltaG(0) value was most negative for cholesterol among the solubilizates studied, which indicated that cholesterol was thermodynamically stabilized most by solubilization into the bile salt micelles.

Bile Acids and Salts↗
PubMed2005

Influence of N-dodecyl-N,N-dimethylamine N-oxide on the activity of sarcoplasmic reticulum Ca(2+)-transporting ATPase reconstituted into diacylphosphatidylcholine vesicles: efects of bilayer physical parameters.

Sarcoplasmic reticulum Ca-transporting ATPase (EC 3.6.1.38) was isolated from rabbit white muscle, purified and reconstituted into vesicles of synthetic diacylphosphatidylcholines with monounsaturated acyl chains using the cholate dilution method. In fluid bilayers at 37 degrees C, the specific activity of ATPase displays a maximum (31.5+/-0.8 IU/mg) for dioleoylphosphatidylcholine (diC18:1PC) and decreases progressively for both shorter and longer acyl chain lengths. Besides the hydrophobic mismatch between protein and lipid bilayer, changes in the bilayer hydration and lateral interactions detected by small angle neutron scattering (SANS) can contribute to this acyl chain length dependence. When reconstituted into dierucoylphosphatidylcholine (diC22:1PC), the zwitterionic surfactant N-dodecyl-N,N-dimethylamine N-oxide (C12NO) stimulates the ATPase activity from 14.2+/-0.6 to 32.5+/-0.8 IU/mg in the range of molar ratios C12NO:diC22:1PC=0/1.2. In dilauroylphosphatidylcholines (diC12:0PC) and diC18:1PC, the effect of C12NO is twofold-the ATPase activity is stimulated at low and inhibited at high C12NO concentrations. In diC18:1PC, it is observed an increase of activity induced by C12NO in the range of molar ratios C12NO:diC18:1PC< or =1.3 in bilayers, where the bilayer thickness estimated by SANS decreases by 0.4+/-0.1 nm. In this range, the 31P-NMR chemical shift anisotropy increases indicating an effect of C12NO on the orientation of the phosphatidylcholine dipole N(+)-P- accompanied by a variation of the local membrane dipole potential. A decrease of the ATPase activity is observed in the range of molar ratios C12NO:diC18:1PC=1.3/2.5, where mixed tubular micelles are detected by SANS in C12NO+diC18:1PC mixtures. It is concluded that besides hydrophobic thickness changes, the changes in dipole potential and curvature frustration of the bilayer could contribute as well to C12NO effects on Ca(2+)-ATPase activity.

Animals↗