Cholic Acid Derivatives Research Articles

Self-aggregation mechanism of a naphthylamide cationic derivative of cholic acid. From fibers to tubules

The aggregation behavior of a cationic derivative of cholic acid {[3β,5β,7α,12α]-3-(2-naphthoylamino)-7,12-dihydroxycholan-24-triethylamonium iodide} has been studied by surface tension measurements, fluorescence spectroscopy, transmission electronic microscopy (TEM), and circular dichroism. The critical aggregation concentration, the fraction of bound counterions and thermodynamic parameters for the formation of aggregates have been determined, as well as the morphology of the aggregates. TEM images support a consecutive transformation mechanism from fibers to tubules, these having a well-defined geometry and being the only structure observed at the end of the process. Intermediate observed structures are helical ribbons.

Catanionic Gels Based on Cholic Acid Derivatives

In this paper, the preparation and characterization of an anionic and a cationic surfactant obtained by chemical modifications of a natural bile acid (cholic acid) are reported. The bile acid was modified by introducing a diamine or a dicarboxylic aromatic residue on the lateral chain. The pure cationic surfactant self-assembles in a network of fibers with a cross-section gyration radius of about 15.1 Å, providing hydrogels with a pH-dependent compactness. On the other hand, the anionic molecule gives rise to prolate ellipsoid micelles. Homogeneous catanionic mixtures have also been obtained, with molar fraction of each surfactant ranging from 0.125 to 0.875. At total surfactant concentration of 0.05% (w/v), the mixtures form gels of fibrils partially arranged in secondary twisted superstructures. Comparison of this concentration with the minimum gelation concentration of the pure cationic derivative (0.16% w/v) suggests that, in the mixtures, the presence of the electrostatic component in self-assembly of the molecules allows the formation of gels starting from more dilute samples. In view of these achievements, this work suggests that catanionic mixtures can be exploited to enhance the efficiency of gelators.

AB0108 Effects of cholic acid and its derivatives in experimental arthritis.

BackgroundBile acids play an important role in cholesterol metabolism and act as intestinal detergents for digestion and absorption of fats and fat-soluble vitamins. Disruption of bile flow causes cholestatic liver...

Bile Acid Derived Tropos Vaulted Bi­naphth­ylphosphites: Synthesis, Stereo­chemical Characterization and Complexation to Rhodium

AbstractThree different 2,2′‐binaphthylphosphites were synthesized, starting from suitable derivatives of cholic or deoxycholic acids and 1,1′‐dihydroxy‐2,2′‐binaphthyl, and their stereochemical features were analyzed by CD and NMR spectroscopy. The spectroscopic data clearly demonstrate the capability of the cholestanic backbone to induce a M prevalent screw sense to the flexible binaphthyl moiety, giving rise to tropos ligands. The extent of the prevalence of the M sense of twist depends on the position at which the binaphthylphosphite moiety is linked on the bile acid skeleton. The three phosphites were mixed with [Rh(COD)2][BF4] and the resulting complexes were analyzed by variable temperature 31P NMR spectroscopy, thereby obtaining information on their stereochemical characteristics, which reflect the different asymmetric induction capability of the ligands.

New propanoyloxy derivatives of 5β-cholan-24-oic acid as drug absorption modifiers

A series of final twelve propanoyloxy derivatives of 5β-cholan-24-oic acid (O-propanoyl derivatives of cholic acid) as potential drug absorption modifiers (skin penetration enhancers, intestinal absorption promoters) was generated by multistep synthesis. Structure confirmation of all generated compounds was accomplished by 1H NMR, 13C NMR, IR and MS spectroscopy methods. All the prepared compounds were analyzed using RP-TLC, and their lipophilicity (RM) was determined. The hydrophobicity (log P), solubility (log S), polar surface area (PSA) and molar volume (MV) of the studied compounds were also calculated. All the target compounds were tested for their in vitro transdermal penetration effect and as potential intestinal absorption enhancers. The cytotoxicity of all the evaluated compounds was evaluated against normal human skin fibroblast cells. Their anti-proliferative activity was also assessed against human cancer cell lines: T-lymphoblastic leukemia cell line and breast adenocarcinoma cell line. One compound showed selective cytotoxicity against human skin fibroblast cells and another compound possessed the highest cytotoxicity against all the tested cell lines. Only one compound expressed anti-proliferative effect on leukemia cancer cells without affecting the growth of normal cells, which should be promising in potential development of new drugs. Most of the target compounds showed minimal anti-proliferative activity (IC50>37μM), indicating they would have moderate cytotoxicity when administered as chemical absorption modifiers. The relationships between the lipophilicity/polarity and the chemical structure of the studied compounds as well as the relationships between their chemical structure and enhancement effect are discussed in this article.

Dansyl-Labeled Cholic Acid as a Tool To Build Speciation Diagrams for the Aggregation of Bile Acids

Bile acids (BAs) are a family of natural steroids biosynthesized from cholesterol in the liver that tend to form aggregates in solution. A fluorescent derivative of cholic acid, namely 3α-Dns-ChA, was employed as a reporter to establish the speciation diagrams of the most abundant BAs that can be found mainly in three microenvironments, solution, and primary and secondary aggregates. The developed methodology is based on the analysis of the combined steady-state and time-resolved experiments performed on 3α-Dns-ChA whose emission behavior was found to be strongly medium dependent. In particular, speciation diagrams of sodium glycocholate (NaGCh), sodium taurocholate (NaTCh), sodium chenodeoxycholate (NaCDCh), sodium glycochenodeoxycholate (NaGCDCh), sodium deoxycholate (NaDCh), and sodium ursodeoxycholate (NaUDCh) were successfully built up.

Crystal structure of head-to-head dimers of cholic and deoxycholic acid derivatives with different symmetric bridges

The crystal structure of three head-to-head dimers (having two cholic acid or deoxycholic acid units) linked at carbon atoms C3 by aromatic or alkyl bridges is studied. An internal coordinates system is necessary for describing the relative orientation in the space of the two bile acid residues. Five angles (three torsion and two common ones) are necessary for defining the relative position of both steroid residues in space. Carbon atoms C3 (which always carries a α-hydroxy group in natural bile acids), and C10 and C13 (which always carry β-methyl groups) of each steroid residue are suitable for this purpose. Furthermore, the distance between each C3 carbon atoms of both steroid residues will allow one to locate the steroids in space. The three dimers selected provide a large range of values for these angles. The packing, hydrogen bond network, and location of guest in the three crystals are discussed.

Two New Cholic Acid Derivatives from the Marine Ascidian-Associated Bacterium Hasllibacter halocynthiae

The investigation of secondary metabolites in liquid cultures of a recently discovered marine bacterium, Hasllibacter halocynthiae strain KME 002T, led to the isolation of two new cholic acid derivatives. The structures of these compounds were determined to be 3,3,12-trihydroxy-7-ketocholanic acid (1) and 3,3,12-trihydroxy-7-deoxycholanic acid (2) through HRFABMS and NMR data analyses.

Exploitation of a Laccase/Meldola’s Blue System for NAD+ Regeneration in Preparative Scale Hydroxysteroid Dehydrogenase‐Catalyzed Oxidations

AbstractAn enzymatic regeneration system consisting of laccase and the 2H+/2e− redox mediator Meldola’s blue (MB) was developed for the efficient oxidation of reduced nicotinamide adenine dinucleotide (NADH) cofactor and employed in the gram‐scale oxidation of cholic acid (1) to its 7‐keto derivative (1a) by 7α‐hydroxysteroid dehydrogenase (7α‐HSDH) in an aqueous, buffered reaction system. The regenerating enzyme, laccase, reduces molecular oxygen as terminal 4H+/4e− acceptor to water and concomitantly reoxidizes NADH via MB at high turnover rates. The regeneration system was successfully applied to quantitatively convert 1 (50 mM, 20.4 g) into 1a with a space‐time yield of 5.8 mmol L−1 h−1. High total turnover numbers were achieved for 7α‐HSDH (4.2×105) and laccase (1.1×106). Alternatively, the regeneration system was employed on the conversion of the methyl ester derivative of cholic acid (2, 200 mM, 5.9 g) dissolved in isopropyl acetate as organic solvent in a biphasic system. Due to the high concentration of 2 and the excellent performance of the enzymatic cascade reaction even under the harsh process conditions, space‐time yields of up to 20 mmol L−1 h−1 (8.5 g L−1 h−1) of the produced 7‐keto derivative 2a were obtained. The irreversibility and high driving force of the regenerating reaction allowed quantitative conversions and easy product recovery.

Dual-bioactivity-based liquid chromatography-coupled quadrupole time-of-flight mass spectrometry for NF-κB inhibitors and β2AR agonists identification in Chinese Medicinal Preparation Qingfei Xiaoyan Wan

Traditional Chinese medicine (TCM) preparations have been used as an effective multitarget strategy for the treatment of complex diseases; however, their bioactive constituents are undefined and difficult to identify. In this study, a simple and dual-target method based on ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry combined with dual-bioactive (NF-κB and β(2)-adrenergic receptor) luciferase reporter assay systems was developed for the rapid determination of various bioactive compounds of TCM preparations. Qingfei Xiaoyan Wan, a TCM preparation used for the clinical therapy of asthma, was analyzed with this method. Potential anti-inflammatory and spasmolytic constituents were screened using NF-κB and β(2)-adrenergic receptor activity luciferase reporter assay systems and simultaneously identified according to the time-of-flight mass spectrometry data. One β(2)-adrenergic receptor agonist (ephedrine) and four structural types of NF-κB inhibitors (arctigenin derivatives, cholic acid derivatives, chlorogenic acid, and sinapic acid) were characterized. Tracheloside was considered a new NF-κB inhibitor. Further cytokine and chemokine detection confirmed the anti-inflammatory effects of the potential NF-κB inhibitors. The integration of ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry and dual-bioactive human cell functional evaluation systems proved to be a simple and effective strategy for the rapid screening of various bioactive compounds in TCM preparations used to treat complex diseases.

Synthesis of 99mTc-cationic steroid antimicrobial-107 and in vitro evaluation

Ceragenins/cationic steroid antimicrobials (CSAs) are a group of cholic acid derivatives with many properties that make them favourable for application as anti-infective agents. CSA-107 is also a member of this group that was labelled with 99mTc by using SnCl2·2H2O as reducing agent and Na–K tartrate as transchelating agent. Labelling efficiency was optimized by varying the amount of reducing agent, pH, and time of incubation. Labelling efficiency and the stability of 99mTc-CSA-107 in human serum was determined by paper and thin layer chromatography, which were >95 and >90 % respectively. In vitro binding of 99mTc-CSA-107 was >95 % determined by using Staphylococcus aureus bacteria.

Ice-like encapsulated water by two cholic acid moieties

Starting from the structure of ice (in which each water molecule is surrounded by other four water molecules forming a tetrahedron with a value of 4.51Å for the edge O–O distance), and the knowledge that this value also corresponds to the O7–O12 distance of the skeleton of cholic acid, it is hypothesized that two steroid cholic acid moieties, with an appropriate steroid–steroid distance and a belly-to-belly orientation, could encapsulate a single water molecule between them. To check this hypothesis two succinyl derivatives of cholic acid (a monomer and the related head–head dimer in which the succinyl group is the linking bridge) were designed. The expected “ice-like” structure is found in the crystal of the dimer. There is a hydrogen bond synergy between those participating in the “ice-like” structure, and those in which the bridge is involved with the O7–H hydroxy group and the side chain of the steroid.

Nanomolar Cellular Antisense Activity of Peptide Nucleic Acid (PNA) Cholic Acid (“Umbrella”) and Cholesterol Conjugates Delivered by Cationic Lipids

Limited cellular uptake and low bioavailability of peptide nucleic acids (PNAs) have restricted widespread use of PNAs as antisense/antigene agents for cells in culture and not least for in vivo applications. We now report the synthesis and cellular antisense activity in cultured HeLa pLuc705 cells of cholesterol and cholic acid ("umbrella") derivatives of splice correction antisense PNA oligomers. While the conjugates alone were practically inactive up to 1 μM, their activity was dramatically improved when delivered by a cationic lipid transfection agent (LipofectAMINE2000). In particular, PNAs, conjugated to cholesterol through an ester hemisuccinate linker or to cholic acid, exhibited low nanomolar activity (EC(50) ∼ 25 nM). Excellent sequence specificity was retained, as mismatch PNA conjugates did not show any significant antisense activity. Furthermore, we show that increasing the transfection volume improved transfection efficiency, suggesting that accumulation (condensation) of the PNA/lipid complex on the cellular surface is part of the uptake mechanism. These results provide a novel, simple method for very efficient cellular delivery of PNA oligomers, especially using PNA-cholic acid conjugates which, in contrast to PNA-cholesterol conjugates, exhibit sufficient water solubility. The results also question the generality of using cholic acid "umbrella" derivatives as a delivery modality for antisense oligomers.

Antibody-Mediated Inhibition of Fibroblast Growth Factor 19 Results in Increased Bile Acids Synthesis and Ileal Malabsorption of Bile Acids in Cynomolgus Monkeys

Fibroblast growth factor 19 (FGF19) represses cholesterol 7α-hydroxylase (Cyp7α1) and inhibits bile acid synthesis in vitro and in vivo. Previous studies have shown that anti-FGF19 antibody treatment reduces growth of colon tumor xenografts and prevents hepatocellular carcinomas in FGF19 transgenic mice and thus may be a useful cancer target. In a repeat dose safety study in cynomolgus monkeys, anti-FGF19 treatment (3-100 mg/kg) demonstrated dose-related liver toxicity accompanied by severe diarrhea and low food consumption. The mechanism of anti-FGF19 toxicity was investigated using in vitro and in vivo approaches. Our results show that anti-FGF19 antibody had no direct cytotoxic effect on monkey hepatocytes. Anti-FGF19 increased Cyp7α1, as expected, but also increased bile acid efflux transporter gene (bile salt export pump, multidrug resistant protein 2 [MRP2], and MRP3) expression and reduced sodium taurocholate cotransporting polypeptide and organic anion transporter 2 expression in liver tissues from treated monkeys and in primary hepatocytes. In addition, anti-FGF19 treatment increased solute transporter gene (ileal bile acid-binding protein, organic solute transporter α [OST-α], and OST-β) expression in ileal tissues from treated monkeys but not in Caco-2 cells. However, deoxycholic acid (a secondary bile acid) increased expression of FGF19 and these solute transporter genes in Caco-2 cells. Gas chromatography-mass spectrometry analysis of monkey feces showed an increase in total bile acids and cholic acid derivatives. These findings suggest that high doses of anti-FGF19 increase Cyp7α1 expression and bile acid synthesis and alter the expression of bile transporters in the liver resulting in enhanced bile acid efflux and reduced uptake. Increased bile acids alter expression of solute transporters in the ileum causing diarrhea and the enhanced enterohepatic recirculation of bile acids leading to liver toxicity.

Synthesis and spectroscopic studies of new bile acid derivatives linked by a 1,2,3-triazole ring

A novel method for the synthesis of cholic acid derivatives has been developed using ‘click chemistry’. Intermolecular 1,3-dipolar cycloaddition of the propargyl ester and azide groups of 3α-azidoacetoxy-7α,12α-diformyloxy-5β-cholan-24-oate gave a new dimer and oligomer linked by a 1,2,3-triazole ring. The structures of the products were confirmed by spectral ( 1H NMR, 13C NMR, and FT-IR) analysis, mass spectrometry and PM5 semiempirical methods. Estimation of the pharmacotherapeutic potential has been accomplished for the synthesized compounds on the basis of Prediction of Activity Spectra for Substances (PASSs).

Additional criterion for the determination of the handedness of 21 helices in crystals of bile acids: Crystal structure of a tert‐butylphenyl derivative of cholic acid

[3β,5β,7α,12α]-3-(4-t-Butylbenzoilamine)-7,12-dihydroxycholan-24-oic acid was synthesized and recrystallized from chlorobenzene and acetone. Orthorhombic P2(1)2(1)2(1) and monoclinic P2(1) crystals were obtained, respectively, and both crystals include solvent and water molecules with a 1:1:1 stoichiometry. In the second case, there are two nonequivalent molecules of the steroid in the unit cell. In both crystals, a crossing structure results for the molecular packing, stabilized by hydrogen bonds between the steroid molecules. In the second crystal, water links steroid molecules of the same type, which are not directly connected through hydrogen bonds. The steroid molecules define helicoidal assemblies along 2(1) screw axes. The handedness in the crystal in chlorobenzene is unambiguously defined by following the criterion proposed by Miyata et al., as the steroids are in a belly-to-belly disposition around the axis. This motif does not appear in the crystal in acetone, and other criterion is required. On the basis of the fact that a staircase and its banister have the same handedness and using the crystal in chlorobenzene as reference, the additional criterion has been established. According to it, in the absence of a belly-to-belly orientation, the handedness must be defined by keeping the bile acid with its right side oriented toward the axis. Pitch angles of the helices and tilt angles of the molecules are also determined.

The role of the acquisition methods in the analysis of natural and synthetic steroids and cholic acids by gas chromatography–mass spectrometry

An exhaustive GC–MS acquisition study was performed, for the simultaneous analysis of natural and synthetic steroids and cholic acids (in order to insert them into the last tierce of our multiresidue analysis system), such as androsterone, β-estradiol, transdehydroandro-sterone, transdehyroandrosterone, mestranol, dihydrotestosterone, ethinylestradiol, testosterone, norethisterone, estriol, 4-androstene-3,17-dione, gestodene, levonorgestrel, etonogestrel, coprostanol, progesterone, cholesterol, medroxyprogesterone-acetate, lithocholic acid, stigmasterol, cholic acid, chenodeoxycholic acid, β-sitosterol, ursodeoxycholic acid, 3-hydroxy-7-ketocholic acid and dehydrocholic acid, in total 26 compounds. As novelties to the field, for the trimethylsilyl (TMS) oxime ether/ester derivatives of steroids and cholic acids, at first, a tandem mass spectrometric (MS/MS), multiple reaction monitoring (MRM) type acquisition method has been developed in a single run; also for the first time, the three acquisition techniques, the full scan (FS), the selective ion monitoring (SIM), in our case the multiple ion monitoring (MIM) and the currently optimized MRM methods, have been compared; all three, in parallel, under strictly the same derivatization/instrumental conditions, both in matrix free solutions and municipal wastewater from two Hungarian wastewater treatment plants (WWTPs). Critical evaluation of the three acquisition protocols was collated on their analytical performances and validated under the same conditions. The data of six point calibration curves for FS, MIM and MRM methods, showed that both R 2 (0.9995, 0.9858, 0.9975) and RSD (5.3, 5.8, 5.0), for two parallel derivatizations, each injected three times, proved to be independent of the acquisition processes. Whereas, for the method limit of quantification (LOQ) and the instrument limit of quantification (ILQ) values showed considerable differences. LOQ data, were decreasing in the FS, MIM, MRM line (expressed in ng/L), for all steroids and cholic acids. The same trend was determined in terms of the ILQ values. The practical utility of the optimized acquisition techniques was confirmed by the quantitation of the steroids and cholic acids contents of wastewater samples. Results confirmed the importance of the MRM acquisition method, even in comparison to the MIM one: with particular interest in selected cases: avoiding the extreme overestimation of the β-estradiol (156–1325%) and that of the ethinylestradiol (582–831%) concentrations in the wastewater samples.

Steroid/Triterpenoid Functional Molecules based on “Click Chemistry”

This Focus Review highlights the design and synthesis of various functional molecules based on steroid/triterpenoid as building blocks through the copper-catalyzed azide-alkyne cycloaddition (CuAAC) "click" reaction, as well as their applications in bioactivity, recognition, and assembly. This method shows great promise to allow us to develop novel molecules with characteristic functions using the CuAAC "click" reaction.

A Desirable Hole‐Conducting Coadsorbent for Highly Efficient Dye‐Sensitized Solar Cells through an Organic Redox Cascade Strategy

Over the past decade, dye-sensitized solar cells (DSSCs) based on nanocrystalline mesoporous metal oxides (typically TiO2) have been intensively studied and developed as a promising, low-cost alternative to conventional silicon photovoltaic devices. The components of such DSSCs are a dye sensitizer, a TiO2 metal oxide coated on conductive glass, a redox electrolyte couple, and a counter electrode. As illustrated in Scheme 1, the power-conversion efficiency of DSSCs is strongly dependent upon the minimization of charge recombination losses at the TiO2/dye/electrolyte interface (pathways 3 and 4). There are two recombination pathways of importance in DSSCs, in which electrons photoinjected into the TiO2 electrode can recombine with either dye cations or with redox electrolytes. Moreover, such charge recombination leads to losses in both the short-circuit photocurrent (Jsc) and the open-circuit photovoltage (Voc), resulting in a decrease in overall energy conversion efficiency (h). To reduce the possible charge recombination pathways occurring at the TiO2/dye/electrolyte interface, several kinds of additives, such as decylphosophonic acid (DPA), dineohexyl bis(3,3-dimethylbutyl)phosphinic acid (DINHOP), and chenodeoxycholic acid (CDCA) have been introduced to adsorb onto the TiO2 surface. [3] Among them, for example, cholic acid (CA) derivatives as coadsorbents in DSSCs, based on a Ru–pyridyl complex, courmarin, porphyrin, phthalocyanine, and naphthalocyanine dye, have been investigated well. Deoxycholic acid (DCA) is often used as a coadsorbent to break up organic and Ru–dye aggregates and hence to significantly improve Voc and Jsc. [5,9] Moreover, alternative approaches directed toward the minimization of recombination losses have been extensively studied by not only the insertion of a metal oxide blocking layer, but also by energetic cascades for multistep hole conductors (HC), as well as superior molecular sensitizer dyes and the insertion of a barrier layer between the sensitizer dye and the HC. To date, however, the desired redox intermediate mediators between the dye and I /I3 redox electro-

Dansyl Labeling To Modulate the Relative Affinity of Bile Acids for the Binding Sites of Human Serum Albumin

Binding of natural bile acids to human serum albumin (HSA) is an important step in enterohepatic circulation and provides a measure of liver function. In this article, we report on the use of four dansyl (Dns) derivatives of cholic acid (ChA) to demonstrate a regiodifferentiation in their relative affinity for the two binding sites of HSA. Using both steady-state and time-resolved fluorescence, formation of Dns-ChA@HSA complexes was confirmed; the corresponding binding constants were determined, and their distribution between bulk solution and HSA microenvironment was estimated. By means of energy transfer from Trp to the Dns moiety, donor-acceptor distances were estimated (21-25 Å) and found to be compatible with both site 1 and site 2 occupancies. Nevertheless, titration using warfarin and ibuprofen as specific displacement probes clearly indicated that 3α- and 3β-Dns-ChA bind to HSA at site 2, whereas their C-7 regioisomers bind to HSA at site 1. Furthermore, the C-3-labeled compounds are displaced by lithocholic acid, whereas they are insensitive to ChA, confirming the assumption that the former binds to HSA at site 2. Thus, Dns labeling provides a useful tool to modulate the relative affinity of ChA to the major binding sites of HSA and, in combination with other fluorescent ChA analogs, to mimic the binding behavior of natural bile acids.