Determination of bile acids in serum and bile by a modified gas chromatographic glass capillary technique

Summary A modified gas chromatographic glass capillary technique for determination of five major bile acids (Cholic acid: CA, Chenodeoxycholic acid: CDCA, Deoxycholic acid: DCA, Lithocholic acid: LCA and Ursodeoxycholic acid: UDCA) has been developed after preliminary extraction with XAD-2 resin. Enzymatic hydrolysis prevents the formation of interferring degradation products. Ether extraction with centrifugation eliminates water soluble interferring substances. Derivatization to hexafluorpropyl- instead of methyl esters results in better separation, shortens analysis time and prolongs the life span of the column.     

Biomaterials made of bile acids

The use of natural compounds in the preparation of new materials can improve the biocompatibility of the materials and avoid any potential toxicity of the degradation products when used for biomedical applications. Bile acids are amphiphilic molecules biosynthesized in the liver. They are used to prepare various polymers and oligomers. These polymers made of bile acids are promising materials in both biomedical and pharmaceutical fields.     

基于胆酸的功能性分子的研究进展

胆酸是存在于人和动物体内的天然分子,由胆固醇在肝脏中合成．其结构上具有亲水的一面和憎水的一面,以其作为结构单元可以合成各种各样的功能性分子．这些分子因其独特的物理化学特性,被广泛应用到化学、生物医学等领域．本文回顾了近几年来国内外研究人员以胆酸为结构单元合成的高分子和低聚物及这些分子在生物医用材料方面的应用．     

Quantification of bile acids directly from plasma by MALDI-TOF-MS

Matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry (MS) has proved to be a useful method for the quantification of bile acids directly from plasma. Six cholic acid derivatives were selected for analysis: taurocholic acid, taurochenodeoxycholic acid, taurolithocholic acid, glycocholic acid, glycochenodeoxycholic acid, and glycolithocholic acid. Solid-phase extraction (SPE) columns were used to preconcentrate and purify the plasma samples. Calibration curves averaged from 3 days were obtained for the bile acids, and then tested for their ability to accurately determine concentrations from one measurement. In summary, a simple, rapid method has been developed for the quantification of bile salts from plasma by MALDI-MS with SPE cleanup.     

Characterization of bile acids and fatty acids from ox bile in oil paintings by gas chromatography-mass spectrometry

Characterization of ox bile, traditionally used in painting, is of interest in the fields of archaeometry and conservation and restoration of works of art. Bile acids, fatty acids (F), and cholesterol found in ox bile have been identified using a derivatization method that combines the formation of ethyl esters from the carboxylic groups and the trimethylsilyl ethers from hydroxyl groups. This method of analysis is consistent with these others proposed by the authors to analyze drying oils, proteins, and diterpenic resins usually used as binders and varnishes by the painters. Bile acids from binary samples such as animal glue/ox bile, casein/ox bile and Arabic gum/ox bile have been successfully analyzed using the proposed method. Finally, a method of analysis of mixtures of drying oil and ox bile has been also proposed attempting to quantitatively characterize samples in which ox bile was added to the drying oil for increasing the surfactant properties.     

新型含联萘基团的旋光聚氨酯的制备与性能表征

以旋光联萘二酚(BINOL)和甲苯-2,4-二异氰酸酯(TDI)为原料, 采用氢转移加成聚合法制备了含联萘基团的新型旋光聚氨酯(S-BPU和R-BPU), 并用FTIR, 1H NMR, UV-Vis, CD和DSC/TGA等手段对该聚氨酯进行了结构和性能表征. 结果表明, 当BINOL的光学纯度逐渐增加时, BPU的旋光度和特性粘度逐渐增大, S-BPU和R-BPU的旋光度最高可分别达到-78°和＋54.6°, 具有较高的旋光能力; S-BPU和R-BPU的玻璃化转变温度(Tg)分别达到258.4和286.6 ℃, 热分解温度(Td)分别为305.6和323.6 ℃, 热分解温度比通常的PU材料提高了100 ℃ 左右, 显示了较好的热稳定性; R-BPU和S-BPU的红外发射率分别为0.682和0.618, 显示了较低的红外发射率.     

Miscible blends through hydrogen bonding: effects on polymer properties

Miscible blends through hydrogen bonding have been intensively studied. The effects of a variety of miscible hydrogen bonded polymer blends on properties such as thermal and thermal oxidative stability, moisture sensitivity, modulus and glass transition temperature are discussed. In addition, the preparation of semi-interpenetrating polymer networks (IPNs) and studies of the effect of crosslinking on the miscibility in hydrogen bonded polymer blends are reviewed.     

Chemical properties of bile acids: III. Bile acid structure and solubility in water

The temperature dependence of the solubilities in water at pH 3.00 of a representative series of ten cholanoic acids (bile acids) were measured over the temperature range 10 to 50°C. The solubilities ranged from 5×10^–8M for 3-hydroxy-5-cholanoic acid (lithocholic acid) to 2×10^–3M for 3-7-12-trihydroxy-5-cholanoic acid (ursocholic acid). The solubilities increased with temperature and were found to be dependent on the number, position, and orientation of the hydroxyl groups. The hydroxyl groups affect solubility both by forming hydrogen bonds with the solvent and by reducing the hydrophobic area of the steroid nucleus. The enthalpic H⁰ and entropic S⁰ contributions to ⁰ associated with the dissolution process were obtained from the temperature dependence of the solubilities. A qualitative interpretation of the thermodynamic parameters in relation to bile acid structure is also presented.     

Side-chain modified bile acids: chromatographic separation of 23-methyl epimers

Owing to the re-flourished interest towards the bile acids (BAs) as versatile signalling hormones endowed with diverse endocrine functions, the development of reliable analytical protocols monitoring the synthesis of new BA-based receptor modulators, still represents a cogent concern. On this basis, for the first time, a HPLC study has been engaged with the aim to set up suitable chromatographic conditions for the analysis of three different epimeric couples of 23-methyl-substituted unconjugated BAs. Three different methods (one for each couple) have been successfully established and then validated. Good precision and accuracy (evaluated both in the short and long period) as well as appreciably low LOD and LOQ values have turned out. Moreover, the engagement of an evaporative light scattering detector (ELSD) has proven its high effectiveness for the analysis of such steroidal species.     

Enhanced mechanical and shape memory properties of polyurethane block copolymers chain-extended by ethylene diamine

Effect on shape memory and mechanical properties of polyurethane (PU) copolymers by changing the chain extender from 1,4-butanediol (BD) to ethylenediamine (ED) was investigated. PU copolymers composed of the different ratio of hard and soft segment were prepared and characterized by IR, DSC, XRD, and UTM. Glass transition temperature of PU increased to room temperature range by adopting ED as a chain extender. The XRD peak pattern changed with hard segment content. ED type PU achieved the high mechanical properties at lower hard segment content than BD type PU. Especially, strain at break of ED type significantly improved compared to BD type. Shape recovery rates were similar for both types of PU, but ED type showed better shape retention rate than BD type. The reason for the differences between two types of PU is discussed in this paper.     

胶束电动毛细管色谱间接紫外光检测法分离胆汁酸

利用间接紫外光检测法在254 nm进行胆汁酸胶束电动毛细管色谱分离的研究.在对氨基苯磺酸为背景电解质和十二烷基硫酸钠作胶束的体系中,加入高浓度的尿素,有效地改善了两类胆汁酸5组份的分离度,在优化分离缓冲体系10 mmol/L对氨基苯磺酸-5 mmol/L硼砂-30 mmol/LSDS-7 mol/L尿素-10%乙醇(pH 7.5)中,13 min内获得基线分离,分离效率为8.4×104～1.1×105.所建立的方法无需衍生化处理,为胆汁酸的分离提供了新的通用的方法.     

Analysis of bile acids in human biological samples by microcolumn separation techniques: A review

Bile acids are a group of compounds essential for lipid digestion and absorption with a steroid skeleton and a carboxylate side chain usually conjugated to glycine or taurine. Bile acids are regulatory molecules for a number of metabolic processes and can be used as biomarkers of various disorders. Since the middle of the twentieth century, the detection of bile acids has evolved from simple qualitative analysis to accurate quantification in complicated mixtures. Advanced methods are required to characterize and quantify individual bile acids in these mixtures. This article overviews the literature from the last two decades (2000–2020) and focuses on bile acid analysis in various human biological samples. The methods for sample preparation, including the sample treatment of conventional (blood plasma, blood serum, and urine) and unconventional samples (bile, saliva, duodenal/gastric juice, feces, etc.) are shortly discussed. Eventually, the focus is on novel analytical approaches and methods for each particular biological sample, providing an overview of the microcolumn separation techniques, such as high-performance liquid chromatography, gas chromatography, and capillary electrophoresis, used in their analysis. This is followed by a discussion on selected clinical applications.     

高效液相色谱荧光测定及质谱鉴定分析血清中胆汁酸

利用新型荧光试剂1,2-苯并-3,4-二氢咔唑-9-乙基苯磺酸酯(BDEBS)作柱前衍生化试剂,在EclipseXDB-C8色谱柱上,采用梯度洗脱对10种胆汁酸(BAs)荧光衍生物进行了优化分离。95℃下在二甲基亚砜(DMSO)溶剂中以柠檬酸钾作催化剂,衍生反应35min后获得稳定的荧光产物,衍生反应完全。荧光激发和发射波长分别为λex=333nm,λem=390nm。采用大气压化学电离源(APCISource)正离子模式,实现了血清中胆汁酸的定性测定。分析物的定量测定采用荧光法进行。线性回归系数均在0.9996以上,检出限为22.36~44.57×10-15mol。     

Solution conformations of 2-amino-1-hydroxy-2-aryl ethylphosphonic acids and their diethyl esters

Conformations of 2-amino-1-hydroxy-2-aryl ethylphosphonic acids (in D₂O) and their diethyl esters (in CDCl₃ and CD₃OD) were determined by means of NMR on the basis of dependence between observed values of coupling constants (³J_PC, ³J_HH and ³J_PH) and corresponding dihedral angles. In case of diethyl esters we observed that the conformation was stabilised by the formation of the intramolecular hydrogen bond between (NH₂)?(OH) moieties in both solvents, whereas for acids formation of hydrogen bond between NH₃⁺?PO groups predominates.     

Biological fluid screening and confirmation of bile acids by use of an integrated flow-injection-LC-evaporative light-scattering system

Summary An integrated flow-injection-liquid chromatographic system is presented for the screening of biological fluids for bile acids, and for subsequent confirmation. It is based on the use of a flow-injection configuration with an evaporative light-scattering detector (ELSD), for routine screening for the total concentration of the analytes, followed by the individual determination, by liquid chromatography, of only those samples for which the total concentration is close to or above the normal level in healthy individuals. Bile acids are extracted from human serum and urine withn-hexane under acid conditions. After phase separation the organic layer is evaporated to dryness under a stream of nitrogen and redissolved in weakly alkaline solution (pH 8). The aqueous phase is then passed through a miniaturized Amberlite XAD-7 column for preconcentration and clean up, and eluted with acetonitrile-methanol, 65∶35 (v/v). The effluent is introduced directly into the ELSD for determination of the total bile-acid content of the sample. For confirmatory analysis another aliquot of the sample is processed in the screening module and the effluent from the adsorbent column is then directed to the chromatographic column to obtain the bile acid profile of the sample. Good agreement was obtained in the analysis of urine and serum samples by both procedures.     

Pharmacophore model for bile acids recognition by the FPR receptor

Formyl-peptide receptors (FPRs) belong to the family A of the G-protein coupled receptor superfamily and include three subtypes: FPR, FPR-like-1 and FPR-like-2. They have been involved in the control of␣many inflammatory processes promoting the recruitment and infiltration of leukocytes in regions of inflammation through the molecular recognition of chemotactic factors. A large number of structurally diverse chemotypes modulate the activity of FPRs. Newly identified antagonists include bile acids deoxycholic acid (DCA) and chenodeoxycholic acid (CDCA). The molecular recognition of these compounds at FPR receptor was computationally investigated using both ligand- and structure-based approaches. Our findings suggest that all antagonists bind at the first third of the seven helical bundles. A closer inspection of bile acid interaction reveals a number of unexploited anchor points in the binding site that may be used to aid the design of new potent and selective bile acids derivatives at FPR.     

Aqueous bile salt accelerated cascade synthesis of 1,2,3-triazoles from arylboronic acids

A facile, efficient and mild copper catalyzed strategy for cascade synthesis of various 1,4-disubstituted 1,2,3-triazoles from arylboronic acids, sodium azide and alkynes was developed by using aqueous bile salt NaDC solution as an accelerating medium. Low catalyst loading (only 1?mol% Cu source was sufficient for in situ generation of azide followed by azide–alkyne coupling), green solvent, use of bio-surfactant as additive and short reaction time make this protocol highly accessible and environment friendly.     

A theoretical model for the critical micelle concentration of bile salts

Critical micelle concentration (CMC) is a fundamental parameter in the evaluation of the biological activity of natural and synthetic bile salts. The CMC is logarithmically related to the free energy of solute micellization in aqueous solution. Hydrophobic and hydrogen bonding interaction energies were identified as the primary contributors to this free energy and the logarithm of the CMC was modeled as a linear function of relevant chemical group contributions to the solvent accessible molecular surface area of the solute. The structures (three-dimensional atomic coordinates) of 23 mono-, di-, and tri-hydroxyl bile acids were generated and optimized by energy minimization. The accessible surface area for each structure was computed and partitioned according to calculated charge distribution and polar group orientation. Experimental CMC values were fitted to these computed quantities by least squares multiple linear regression. Two regression equations, based on slightly different surface area partition schemes, were derived and compared. Their significance in explaining the aggregation process and in predicting the CMC of new bile salts is discussed.     

Benzyl and tert-butyl carbamate derivatives of 1,ω-amino acids as simple yet efficient gelators

We report the synthesis and a study of the gelation properties of a series of N-protected long-chain amino acids. Especially, benzyl and tert-butyl carbamate derivatives of 11-aminoundecanoic acid in their deprotonated form can gelate polar organic solvents and water at very low concentration (less than 5 mM). This is explained by the contribution of multiple forces—H-bond, van der Waals and ionic interactions—in the gel aggregate formation and stabilization, which is confirmed by the experimental data. Among the series of compounds investigated, only a dimer of 11-aminoundecanoic acid is capable of gelating toluene, which stems from the increased number of hydrogen bonding sites in the main aliphatic chain.