Bile Acid Methyl Esters Research Articles

Investigation of the Potential of Bile Acid Methyl Esters as Inhibitors of Aldo-keto Reductase 1C2: Insight from Molecular Docking, Virtual Screening, Experimental Assays and Molecular Dynamics.

Human aldo-keto reductase 1C isoforms (AKR1C1-C4) catalyze reduction of endogenous and exogenous compounds, including therapeutic drugs, and are associated with chemotherapy resistance. AKR1C2 is involved in metastatic processes and is a target for the treatment of various cancers. Here we used molecular docking to explore the potential of a series of eleven bile acid methyl esters as AKR1C2 inhibitors. Autodock 4.2 ranked 10 of the 11 test compounds above a decoy set generated based on ursodeoxycholic acid, a known AKR1C2 inhibitor, while 5 of these 10 ranked above 94 % of decoys in Autodock Vina. Seven inactives reported in the literature not to inhibit AKR1C2 ranked below the decoy threshold: 5 of these are specific inhibitors of AKR1C3, a related isoform. Using the same parameters, Autodock Vina identified steroidal analogs of AKR1C substrates, bile acids, and AKR1C inhibitors in the top 5 % of a virtual screen of a natural product library. In experimental assays, 6 out of 11 of the tested bile acid methyl esters inhibited >50 % of AKR1C2 activity, while 2 compounds were strong AKR1C3 inhibitors. Potential off-target interactions with the glucocorticoid receptor were measured using a yeast-based fluorescence assay, where results suggest that the methyl ester could interfere with binding. The top ranking compound based on docking and experimental results showed dose-dependent inhibition of AKR1C2 with an IC50 of ∼3.6 μM. Molecular dynamics simulations (20 ns) were used to explore potential interactions between a bile acid methyl ester and residues in the AKR1C2 active site. Our molecular docking results identify AKR1C2 as a target for bile acid methyl esters, which combined with virtual screening results could provide new directions for researchers interested in synthesis of AKR1C inhibitors.

Synthesis and Spectroscopic Characterisation of O-Chlorocarbonyl Derivatives of Bile Acid Methyl Esters

The synthesis of O-chlorocarbonyl derivatives of a series of bile acid methyl esters is described. The steroidal chloroformate esters were prepared by the reaction of the respective hydroxy derivatives with triphosgene–pyridine in benzene at 25 °C. The O-chlorocarbonyl derivatives were characterised by spectroscopic methods.

Antimicrobial and Lytic Activities of Squalamine Analogs: Effect of Varied Cationic Groups at C3 and Stereochemistry at C7

Squalamine (3β-N-1-{N-[3-(4-aminobutyl)]-1,3-diaminopropane}-7α,24R-dihydroxy-5α-cholestane-24-sulfate), an aminosterol from the dogfish shark (Squalus acanthias), is a potent antimicrobial compound believed to act through plasma membrane lysis. In this report, the antimicrobial activity of squalamine, several structurally related analogs, and bile acid based aminosterols are characterized using two different assays. The structurally similar analogs vary in the stereochemistry at the 3- and 7- substitutents, and also in the length and composition of the polyamine added at C-3. The bile acid analogs are generated by the addition of diaminopropane to C-3 of common bile acid methyl esters. The antimicrobial activity of the analogs was assessed against four bacterial strains. Membrane lytic activity was assayed using large unilamellar vesicles encapsulating a fluorescent calcein dye. Both vesicle lysis and antimicrobial activity of the aminosterols are shown to improve with more cationic groups on the polyamine substituent at C-3. Also, analogs with a 7α-OH substitutent are more effective than their 7β-OH analogs. The bile acid analogs were significantly less active than squalamine.The results suggest that the stereochemistry of the C7-OH group and the A/B ring junction is important in aminosterol activation at the membrane surface.

Bile acid-derived mono- and diketals—synthesis, structural characterization and self-assembling properties

Three oxo-derivatives of bile acid methyl esters have been used as starting compounds in the preparation of novel bile acid monoketals with 1,2-benzenediol (catechol) and 2,3-naphthalenediol, as well as mono- and diketals with pentaerythritol. Monoketals of pentaerythritol showed a tendency to form thermoreversible gels in many aromatic solvents and the methyl lithocholate derivative proved to be a supergelator able to form a gel with t-butylbenzene at a concentration as low as 0.5% w/v. Whereas the naphthalenediol ketals formed film-type materials in the studied solvents, the catechol ketals underwent rapid crystallization into X-ray quality single crystals. Single crystal X-ray structures of the catechol ketals have been determined. The monoketal obtained from methyl-3,7,12-trioxo-5beta-cholan-24-oate (dehydrocholate) revealed to have an unusual packing pattern in its solid state compared to other bile acid derivatives reported in the literature. The synthesis of diketals from pentaerythritol furnished a mixture of two diastereomers which, in the case of the methyl lithocholate derivative, have been separated and the X-ray crystal structure of one isomer resolved.

Facile synthesis of 5β-cholane- sym-triazine conjugates starting from metformin and bile acid methyl esters: Liquid and solid state NMR characterization and single crystal structure of lithocholyl triazine

Four bile acid-triazine conjugates: N 2′, N 2′-dimethyl-6′-(3α-hydroxy-5β-24-norcholyl)-1′,3′,5′-triazine-2′,4′-diamine (lithocholyl triazine, 4a), N 2′, N 2′-dimethyl-6′-(3α,7α-dihydroxy-5β-24-norcholyl)-1′,3′,5′-triazine-2′,4′-diamine (chenodeoxycholyl triazine, 4b), N 2′, N 2′-dimethyl-6′6′-(3α,12α-dihydroxy-5β-24-norcholyl)-1′,3′,5′-triazine-2′,4′-diamine (deoxycholyl triazine) ( 4c), and N 2′, N 2′-dimethyl-6′-(3α,7α,12α-trihydroxy-5β-24-norcholyl)-1′,3′,5′-triazine-2′,4′-diamine (cholyl triazine) ( 4d) have been prepared and characterized by liquid and solid state NMR. An improved synthetic method produced better yields and an easier purification procedure for 4d than reported in the literature. Single crystal structure of 4a is reported: empirical formula C 28H 47N 5O, monoclinic P2 1 space group with unit cell dimensions, a 18.7135(5) Å, b 7.4510(2) Å, c 19.3073(5) Å, β 95.7290(10)°, volume 2678.65(12) Å 3.

Ultrasound accelerated esterification of bile acids

In this study power ultrasound accelerated esterification reactions of some model substances and bile acids were done. In the model reactions the best result was 19-fold increase in the reaction rate when using ultrasound and the temperature was allowed to rise during the irradiation. In the case of bile acid methyl esters a clear increase in the reaction rates was also observed by ultrasonic irradiations.

Synthesis and 13C NMR chemical shift assignments of 2,2'-bipyridine-4,4'-dicarboxylates of bile acid methyl esters

Novel 2,2'-bipyridine-4,4'-dicarboxylates 3a-3d of four bile acid methyl esters have been synthesized from 2,2'-bipyridine-4,4'-dicarboxylic acid 1 and the corresponding bile acid methyl esters (methyl lithocholate 2a, methyl chenodeoxycholate 2b, methyl deoxycholate 2c, and methyl cholate 2d). In addition to the desired products, 3α -(2,6-dichlorophenylcarboxy) bile acid methyl esters 4a-4d were obtained. The structures of 3a-4d have been ascertained by 1 D 1 H and 13 C NMR, 2 D PFG 1 H, 13 C HMQC, and MALDI TOF MS. Molecular weights and 13 C NMR chemical shifts of 3a-4d have been presented. The geometry of 3a has been optimized semi- empirically at the PM3 level and it has been observed that the minimum energy structure of 3a is a open type conformation due to lack of attractive intramolecular electrostatic interactions between the heads of the molecule which would have favoured the formation of cleft type structure. The synthesized bipyridine-bile acid conjugates are interesting structures from the molecular recognition point of view because they could have potential to form complexes with some transition metal ions, for example with silver, cadmium, and ruthenium.

Selective dimethyldioxirane oxidation of bile acid methyl esters

Abstract DMDO oxidation of the hydroxy groups of bile acid methyl esters establishes the positional order of reactivity as 3∼7 > 6 > 12 and supports a mechanism involving CH oxygen insertion through a planar intramolecularly hydrogen bonded transition state.

Imprinted Polymers for Selective Adsorption of Cholesterol from Gastrointestinal Fluids

A series of highly cross-linked terpolymers of methacryloylated cholesterol or bile acid methyl esters, methacrylic acid, and ethyleneglycol dimethacrylate were prepared in the presence or absence ...

Capillary gas–liquid chromatography of acetate–methyl esters of bile acids

Gas–liquid chromatographic separations of acetate–methyl esters of several common bile acids with and without a hydroxyl group at C-6 are compared with those of the corresponding trimethylsilyl ether–methyl esters on a CP-Sil-5 CB capillary column. Unlike the trimethylsilyl ether derivatives, the retention indices of the corresponding acetates were greatly influenced by the number of hydroxyl groups in the ring system. Epimeric hydroxyl groups at carbons 6, 7 as well as 12 increased retention index of the acetate–methyl esters of the bile acids, the effect of the 7β-hydroxyl group being most prominent. The 6β-acetoxyl group increased the retention index more than the 6α-acetoxy group and contrary to the trimethylsilyl ether derivatives, a 6β,7β-diacetoxy group showed larger increase in the retention index than the corresponding 6α,7β-diacetoxy group. The acetate derivatives of bile acid–methyl esters show larger retention times and reduced sensitivity than the corresponding trimethylsilyl ether derivatives. However, gas chromatography of bile acid acetate–methyl esters can be very useful for the characterization of bile acids and for bile acid analysis in the rat where muricholic acids and hyodeoxycholic acid are in abundance, since these bile acids are difficult to resolve from each other and from other common bile acids as the trimethylsilyl ether derivatives.

Potential bile acid metabolites. 23. Syntheses of 3-glucosides of nonamidated and glycine- and taurine-amidated bile acids.

The 3-glucosides of nonamidated lithocholic, chenodeoxycholic, ursodeoxycholic, deoxycholic, and cholic acids, and their double conjugate forms with glycine and taurine were synthesized. The key reactions used were 1) beta-D- glucosidation at C-3 by the Koenigs-Knorr condensation reaction of 3 alpha-hydroxylated bile acid methyl (or p-nitrophenyl) esters with 1 alpha-bromo-1-deoxy-2, 3, 4, 6-tetra-O-acetyl-D-glucopyranose in the presence of cadmium carbonate in refluxing benzene; 2) indirect and direct amidations at C-24 by the activated p-nitrophenyl ester and by the diethylphosphorylcyanide methods, respectively, using glycinate ester and taurine as coupling agents; and 3) simultaneous alkaline hydrolysis of the hydroxyl-protecting and ester groups in both the sugar and aglycone moieties.

Separation of bile acid methyl esters by high‐performance liquid chromatography

AbstractConjugated bile acids, namely glyco‐ and tauro‐3α,6α‐dihydroxy‐5β‐cholanoic acid (hyodeoxycholic acid), 3α,7α‐dihydroxy‐5β‐cholanoic acid (chenodeoxycholic acid), 3α,6α,7α‐trihydroxy‐5β‐cholanoic acid (hyocholic acid) and 3α‐hydroxy‐6‐oxo‐5β‐cholanoic acid (6‐keto‐litocholic acid) were isolated from pig bile, and subsequently transformed into the corresponding methyl esters. Separation of the methyl esters of the isolated bile acids by high‐performance liquid chromatography (HPLC) was accomplished on a ZORBAX‐CN column (Dupont, Boston, MA) withn‐hexane/2‐propanol/methylene chloride (89∶6∶5, by vol) as the mobile phase containing traces (≈1%) of amyl alcohol and water as moderators. HPLC analysis of the methyl esters also showed the presence of methyl 3α‐hydroxy‐6‐oxo‐5α‐cholanoate, which was probably produced in the course of alkaline hydrolysis of the conjugated bile acids.

Studies on steroids: CCLIII. Capillary gas chromatographic behaviour of diethylhydrogensilyl—diethylsilylene derivatives of stereoisomeric bile acids

The capillary gas chromatographic behaviour of diethylhydrogensilyl (DEHS) ethers and/or diethylsilylene (DES) derivatives of fifty bile acids including 4- and 6-hydroxylated compounds is described. The methylene unit (MU) values of methyl and pentafluorobenzyl esters of bile acids were determined as their trimethylsilyl (TMS), dimethylethylsilyl (DMES) ethers and DEHS-DES derivatives. The differences in methylene unit values between the corresponding TMS ethers and DMES ethers or DEHS-DES derivatives were used for estimating the number and stereochemistry of hydroxyl groups on the steroid nucleus. On treatment with the silylating agent N,O-bis (diethylhydrogensilyl)trifluoroacetamide, bile acids possessing isolated hydroxyl in addition to diaxial trans-glycol groups were easily converted into the DEHS ehters, whereas those having a vicinal glycol group except for the diaxial group were converted into cyclic DES derivatives. The mass spectrometric properties obtained with negative-ion chemical ionization detection are discussed.

The use of microwave oven for the rapid hydrolysis of bile acid methyl esters

An efficient and convenient procedure for the hydrolysis of bile acid methyl esters is described. This is achieved by the addition of aqueous lithium hydroxide in methanol/dioxane/tetrahydrofuran (or dimethylformamide) in the microwave oven. Under these conditions the formates as well as the acetate derivatives prepared under microwave irradiation conditions were also hydrolyzed, and the desired bile acids were isolated in 86–94% yield. All these reactions were completed in the microwave oven within 45–60 s.

Lithium hydroxide/aqueous methanol: mild reagent for the hydrolysis of bile acid methyl esters

An efficient and convenient procedure for the hydrolysis of bile acid methyl esters is described. This is achieved by the addition of aqueous lithium hydroxide in methanol/dioxane (or tetrahydrofuran) at room temperature. Under these conditions, the formates as well as the acetate derivatives were also hydrolyzed, and the desired bile acids were Isolated in 86 to 94% yield. (Steroids: 55:233–237, 1990).

Carbon-13 nuclear magnetic resonance spectra of bile acid derivatives. Part II. Mono-, di- and trihydroxy stereoisomers of methyl 5α-cholanoates

Carbon-13 NMR chemical shifts were assigned for the entire set of 26 theoretically possible isomers of mono-, di- and trihydroxylated methyl 5α-cholalnoates (allo series; A/B- trans), which differ from one another in the position and configuration of hydroxyl groups at position 3, 7 and/or 12 in the nucleus. The hydroxy substituent effects on carbons of the parent compound (methyl 5α-cholanoate), the effect of the 17β-cholane side chain on neighboring carbons, and the differences in the chemical shifts between the 5α and 5β (normal series: A/B- cis) bile acid methyl esters were clarified. A restriction of free rotation of the cholane side chain due to the introduction of a 12β-hydroxyl group is also discussed.

Synthesis of the 1 beta-hydroxylated bile acids, unusual bile acids in human biological fluids.

1β-Hydoxylated lithocholic (10a), deoxycholic (10b), chenodeoxycholic (10c) and cholic (10d) acids were synthesized from the corresponding bile acid methyl esters (1a-d) as starting materials. The Δ1-unsaturated ketones (6a, e-g) were prepard from the 3-oxo bile acid esters (2a-d) via reductive debromination of their 2, 4-dibromides (3a, e-g) with chromous acetate and dehydrobromination with lithium carbonate-lithium bromide, and oxidized with alkaline hydrogen peroxide to give the 1β-2β-epoxyketones (7a, e-g). Reductive cleavage of the epoxides (7a, e-g) and subsequent reduction with sodium borohydride afforded the 1β, 3α-dihydroxy compounds (9a, e-g), which were hydrolyzed to the 1β-hydroxylated bile acids (10a-d). 1β, 3α, 12α-Trihydroxy-5β-cholan-24-oic acid (10b) was identified in the urine of healthy men and patients with kidney disease by gas chrmatography-mass spectrometric analysis. Novel 1β, 3α, 7α-trihydroxy-(10c) and 1β, 3α, -7α, 12α-tetrahydroxy-5β-cholan-24-oic acids (10d) were detected in human meconium.

The effect of wheat-bran fibre on the anaerobic metabolism of cholic acid by mixed faecal bacteria

The mode of metabolism of the primary bile acids CA and CDCA by intestinal bacteria involves enzymic attack on the hydroxyl functions. This involves oxidereduction and 7adehydroxylation of the hydroxyl groups, the latter being the predominant reaction in the gut. 7a-Dehydroxylation yields the secondary bile acids DCA and LA from CA and CDCA respectively. The involvement of the secondary bile acids as possible co-carcinogens or promoters (Hill, 198 1) in the colon and the purported protective effect of dietary fibre in colorectal carcinogenesis (Reddy, 1980) has stimulated interest in the metabolic studies of bile acids both in oitro (Morotomi et al., 1979) and in oivo (Pomare et al., 1974). This study examines the effect of wheat-bran fibre on CA metabolism by mixed faecal flora in anaerobic batch culture. Mixed faecal flora from a healthy volunteer was cultured using Brain Heart Infusion broth with 0.02% sodium cholate as substrate and with varying additions of fibre. Cultures were incubated under 80% N,, 10% C02, 10% H2 and sampled at regular intervals for CA metabolites, bacterial analysis and culture pH. In order to quantify CA metabolites 5ml aliquots of culture were extracted with ethyl acetate, dried, methylated with ethereal diazomethane and finally quantified by g.1.c. as trimethyl silyl ether derivatives of the bile acid methyl esters. G.1.c. was conducted on a Pye 304 chromatograph fitted with a 3% OV-1 column, using a temperature gradient of 160-260°C at 4C/min. Bacterial metabolites of CA were identified by gas-chromatography-mass spectrometry on a Dupont 49 1 B series mass spectrometer coupled to a Varian aerograph 2780 gas chromatograph. Results showed that addition of wheat-bran fibre to the culture medium had a marked effect on CA metabolism. In fibre-free cultures the CA substrate was rapidly 7adehydroxylated to DCA with 100% conversion by 47h. During an intermediate period (12-30 h) there was production of keto derivatives of CA, i.e. 7a,l2a-dihydroxy-3-0xoSB-cholanoic acid and 3a, 12a-dihydroxy-7-0xo-5~-cholanoic acid, 3a,7a-dihydroxy-l2-oxo-5~-cholanoic acid, 3,7,12trioxo-SB-cholanoic acid and 3a,7j?, 12a-trihydroxy-SBcholanoic acid. Addition of 1% wheat-bran fibre retarded the metabolism of CA although the same metabolites were produced; 100% conversion of CA to DCA was not evident until 54h. Addition of 2.5% and 5% wheat-bran fibre completely inhibited 7a-dehydroxylation and 3a, 12a-dihydroxy7-oxo-5c this study substantiates these findings. The end products of fermentative carbohydrate breakdown are volatile fatty acids which lower culture pH, hence cultures with added fibre all had a consistently lower pH throughout the incubation

A Simple and Mild Procedure for the Preparation of Bile Acid Methyl Esters

Abstract Bile acid ester are useful intermediates in reaction schemes yielding bile alcohols2–5 and other acid derivatives. Reported methods for the preparation of bi le acid methyl or ethyl esters consist of dissolving the bile acid in a large excess of absolute alcohol (ei ther methanol or ethanol) containing a catalytic amount of concentrated mineral acid (either hydrochloric or sul furic). Alternately bile acid methyl esters have been prepared using diazomethane thus avoid the use of strong mineral acids. This very simple methods, presented howe ver several drawbacks. In the former method, the use of strong mineral acids, expecially hydrochloric acid, on polyhydroxy steroids, such as bile acids, can often cau se the formation of undesirable side products.

Reversed‐phase high‐performance thin‐layer chromatography of mono‐, di‐ and trisubstituted bile acid methyl esters

AbstractA comparative study is reported on separation of series of mono‐, di‐, and trisubstituted methyl 5β‐cholanates, which differ only in the position and stereochemistry of hydroxyl or keto groups at position and stereochemistry of hydroxyl or keto groups at positions C‐3, C‐7, and/or C‐12, by reversed‐phase [with chemically‐bonded (C‐18) silica gel] and normal‐phase (silica gel) high‐performance thin‐layer chromatography (HPTLC). Methnol (or acetonitrile)/water systems were employed as mobile phase. Reversed‐phase HPTLC found to be particulary effective for separation of the stereoisomers of di‐ and trisubstituted compounds whereas the less polar monosubstituted isomers are well resolved in normal‐phase HPTLC.