An improved procedure for the preparation of the β-hydroxy-α-alkyl fatty acid fragment of mycolic acids

An approach to a β-hydroxy-α-alkyl fatty acid intermediate that can be applied in the synthesis of a range of mycolic acids is described.     

Lung surfactant dysfunction in tuberculosis: effect of mycobacterial tubercular lipids on dipalmitoylphosphatidylcholine surface activity

In pulmonary tuberculosis, Mycobacterium tuberculosis bacteria reside in the alveoli and are in close proximity with the alveolar surfactant. Mycolic acid in its free form and as cord factor, constitute the major lipids of the mycobacterial cell wall. They can detach from the bacteria easily and are known to be moderately surface active. We hypothesize that these surface-active mycobacterial cell wall lipids could interact with the pulmonary surfactant and result in lung surfactant dysfunction. In this study, the major phospholipid of the lung surfactant, dipalmitoylphosphatidylcholine (DPPC) and binary mixtures of DPPC:phosphatidylglycerol (PG) in 9:1 and 7:3 ratios were modelled as lung surfactant monolayers and the inhibitory potential of mycolic acid and cord factor on the surface activity of DPPC and DPPC:PG mixtures was evaluated using Langmuir monolayers. The mycobacterial lipids caused common profile changes in all the isotherms: increase in minimum surface tension, compressibility and percentage area change required for change in surface tension from 30 to 10 mN/m. Higher minimum surface tension values were achieved in the presence of mycolic acid (18.2 ± 0.7 mN/m) and cord factor (13.28 ± 1.2 mN/m) as compared to 0 mN/m, achieved by pure DPPC film. Similarly higher values of compressibility (0.375 ± 0.005 m/mN for mycolic acid:DPPC and 0.197 ± 0.003 m/mN for cord factor:DPPC monolayers) were obtained in presence of mycolic acid and cord factor. Thus, mycolic acid and cord factor were said to be inhibitory towards lung surfactant phospholipids. Higher surface tension and compressibility values in presence of tubercular lipids are suggestive of an unstable and fluid surfactant film, which will fail to achieve low surface tensions and can contribute to alveolar collapse in patients suffering from pulmonary tuberculosis. In conclusion a biophysical inhibition of lung surfactant may play a role in the pathogenesis of tuberculosis and may serve as a target for the development of new drug loaded surfactants for this condition.     

The synthesis of a single enantiomer of a major α-mycolic acid of M. tuberculosis

We report a synthesis of a single enantiomer of a mycolic acid from Mycobacterium tuberculosis containing a di-cis-cyclopropane. The method can be simply varied to modify the chain lengths or the absolute stereochemistry of either cyclopropane.     

Synthesis of the methylene bis-tetrahydropyran motif of (−)-exiguolide

A chiral-pool approach for the construction of methylene bis-tetrahydropyran subunit, C₁-C₁₆ fragment, of (−)-exiguolide is described. The synthesis was efficiently accomplished starting from l-glutamic acid and l-aspartic acid involving oxa-Michael reaction and an aldol-driven-reductive etherification as key steps for the formation of tetrahydropyran ring.     

Synthetic epoxy-mycolic acids

We report the synthesis of single enantiomers of epoxy-mycolic acids containing an α-methyl-trans-alkene or a cis-cyclopropane with structures that match those of major isomers of such molecules present in complex mixtures in Mycobacteria such as Mycobacterium fortuitum or Mycobacterium smegmatis     

Application of a new hybrid organic-inorganic monolithic column for efficient deoxyribonucleic acid purification

A new hybrid organic-inorganic monolithic column for efficient deoxyribonucleic acid (DNA) extraction was prepared in situ by polymerization of N-(β-aminoethyl)-γ-aminopropyltriethoxysilane (AEAPTES) and tetraethoxysilane (TEOS). The main extraction mechanism was based on the Coulombic force between DNA and the amino silica hybrid monolithic column. DNA extraction conditions, such as pH, ion concentration and type, and loading capacity, were optimized online by capillary electrophoresis with laser-induced fluorescence detection. Under optimal condition, a 6.0-cm monolithic column provided a capacity of 48 ng DNA with an extraction efficiency of 74 ± 6.3% (X ± RSD). The DNA extraction process on this monolithic column was carried out in a totally aqueous system for the successful purification of DNA and removal of proteins. The PBE2 plasmid could be extracted from Bacillus subtilis (B. subtilis) crude lysate within 25 min, and the purified DNA was suitable for the amplification of a target fragment by polymerase chain reaction. This study demonstrates a new attractive solid-phase support for DNA extraction to meet the increasingly miniaturized and automated trends of genetic analyses.     

基于分枝菌酸的分枝杆菌反相高效液相色谱分型鉴定方法

采用反相高效液相色谱法(HPLC)构建了49种分枝杆菌标准菌株的分枝菌酸指纹图谱库,并对分枝杆菌进行分型鉴定。菌株经培养(对于慢生长分枝杆菌培养3周,快生长分枝杆菌培养1周)后,取两植菌勺的量,皂化1 h后,于4 ℃下储存。通过酸化方法提取分枝菌酸,并用4-溴苯甲酰基溴衍生化,以HPLC分析分枝杆菌衍生物,并以其峰形的分布及峰的相对保留时间、相对峰高为指标对分枝杆菌进行分型鉴定。该法重现性良好,各峰保留时间的相对标准偏差为0.13%～1.07%。根据构建的49种《伯杰细菌鉴定手册》中所载入的分枝杆菌标准菌株的分枝菌酸指纹谱库,发现不同菌种的分枝菌酸的指纹图谱分别具有单簇峰、双簇峰、三簇峰(含多簇峰)的特征。依据相对保留时间和相对峰高的不同,对49种分枝杆菌中的41种进行了分型。结果表明,所建立的反相HPLC法可快速准确地对分枝杆菌进行分型鉴定。     

Fast identification of mycobacterium species by GC analysis with trimethylsulfonium hydroxide (TMSH) for transesterification

Trimethylsulfonium hydroxide (TMSH) reproducibly converts fatty acids bound in, e.g., biomolecules such as phospholipids and/or glycerides, into the corresponding fatty acid methyl esters (FAMEs). The transesterification can be performed at room temperature in a fast single step reaction. Surprisingly, secondary alcohols and mycolic acid cleavage products (MACPs) are also released from mycobacteria under these conditions. The complex reaction mixtures containing FAMEs, MACPs, and secondary alcohols can easily be separated by high resolution temperature-programmed capillary GC. Different species of mycobacteria give rise to characteristic chromatographic patterns and the amount of lipids from a single colony of mycobacteria is sufficient for reliable identification of the bacteria. The profiles of the chromatograms match well those obtained from other sample preparation techniques. The TMSH method of identification of mycobacteria from the patterns of the gas chromatograms is faster and more sensitive than conventional methods, which also involve transesterification. The identification of mycobacterial species by microbiological culture techniques is difficult to perform and requires several weeks.     

Chromatographic fingerprints of industrial toluic acids established for their quality control

The chromatographic fingerprints of industrial o-toluic acid, m-toluic acid and p-toluic acid have been established by HPLC-UV detection according to their impurity groups. HPLC separation of all relative substances involved in the groups was developed on a Kromasil C₁₈ column by using methanol-water-NH₄Ac-HAc buffer (100 mM, pH 4.70) 15/65/20 (v/v/v) as the mobile phase at a flow rate of 1.5 mL/min, and detection was operated by UV adsorption at a wavelength of 254 nm. The ultraviolet spectra corresponding to each chromatographic peak were also recorded for further identification of all components. Whether the limits of relative impurities residues in a toluic acid product are qualified or not can be intuitively estimated by analyzing its chromatogram with comparison to the fingerprint. This protocol has successfully provided some Chinese manufacturers with a simple and feasible method for quality control of toluic acids for industrial use.     

Substituted tubaic acids, new oxidative rotenoid metabolites from Lonchocarpus nicou

A lipophile extract of Lonchocarpus nicou roots afforded two likely O-substituted isomers of the known tubaic acids. Spectroscopic analysis assigned to the former, named (−)-rotoic acid, the new 4-(2,3-dihydro-6,7-dimethoxychromon-3-oxy) tubaic acid structure which differs from (−)-deguoic acid, the latter, by the β-tubaic acid part. Biogenetically, the two compounds could be considered as resulting from the parent rotenone and deguelin, respectively, by oxidative ring-C cleavage.     

3-Oxyanthranilic acid derivatives from Actinomadura sp. BCC27169

Eight new compounds including 9′-[2-amino-3-(4″-O-methyl-α-rhamnopyranosyloxy) phenyl]nonanoic acid (1), 9′-[2-amino-3-(4″-O-methyl-α-ribopyranosyloxy)phenyl] nonanoic acid (2), 11′-[2-amino-3-(4″-O-methyl-α-rhamnopyranosyloxy)phenyl]undecanoic acid (3), 11′-[2-amino-3-(4″-O-methyl-α-ribopyranosyloxy)phenyl]undecanoic acid (4), 8-(4′-O-methyl-α-rhamnopyranosyloxy)-3,4-dihydroquinolin-2(1H)-one (5), 8-(4′-O-methyl-α-ribopyranosyloxy)-3,4-dihydroquinolin-2(1H)-one (6), 8-(4′-O-methyl-α-rhamnopyranosyloxy)-2-methyquinoline (7), and 8-(4′-O-methyl-α-ribopyranosyloxy)-2-methylquinoline (8) were isolated from Actinomadura sp. BCC27169. The chemical structures of these compounds were determined based on NMR and high-resolution mass spectroscopy. The absolute configurations of these monosaccharides were revealed by the hydrolysis of compounds 7 and 8. Compounds 3 and 8 exhibited antitubercular activity at MIC 50 μg/mL. Only compound 3 showed cytotoxicity against KB cell at IC₅₀ 18.63 μg/mL, while other isolated compounds were inactive at tested maximum concentration (50 μg/mL).     

Four new ginkgolic acids from Ginkgo biloba

Four new compounds, 2-hydroxy-6-(12′-hydroxyheptadec-13′(E)-en-1-yl)benzoic acid (1), 2-hydroxy-6-(13′-hydroxyheptadec-11′(E)-en-1-yl)benzoic acid (2), 2-hydroxy-6-(10′-hydroxypentadec-11′(E)-en-1-yl)benzoic acid (3), and 2-hydroxy-6-(11′-hydroxypentadec-9′(E)-en-1-yl)benzoic acid (4) were isolated from the leaves of Ginkgo biloba and the structures of new ginkgolic acids were deduced on the basis of spectroscopic methods and chemical means. Compounds 1 and 2, and 3 and 4 examined as an inseparable mixture of hydroxyl and double bond positional isomers, were ultimately defined by total synthesis. Compounds 1–4 showed moderate lipid droplets accumulation inhibitory activity on mouse pre-adipocyte cell line, MC3T3-G2/PA6.     

Diapolycopenedioic acid xylosyl ester, a novel glyco-C30-carotenoic acid produced by a new marine bacterium Rubritalea squalenifaciens

A novel acyl glyco-carotenoic acid, diapolycopenedioic acid xylosyl ester, was isolated from a marine bacterium Rubritalea squalenifaciens belonging to subdivision 1 of Verrucomicrobia as the major red pigment by using chromatographic methods. The structure of diapolycopenedioic acid xylosyl ester was determined to be 4-[2-O-(12-methyltridecanoyl)-β-xylopyranosyl] hydrogen 4,4′-diapo-ψ,ψ-carotene-4,4′-dioate by analysis of the MS and NMR data for this acid and for the diacetyl diapolycopenedioic acid xylosyl ester. The diapolycopenedioic acid xylosyl ester showed potent antioxidative activity against a lipid peroxidation model.     

Determination of ethylenediaminetetraacetic acid, ethylenediaminedisuccinic acid and iminodisuccinic acid in cosmetic products by capillary electrophoresis and high performance liquid chromatography

A capillary electrophoresis (CE) and a high performance liquid chromatography (HPLC) method are described for the simultaneous determination of ethylenediaminetetraacetic acid (EDTA), S,S′-ethylenediaminedisuccinic acid (EDDS) and R,S-iminodisuccinic acid (IDS) complexing agents as their Fe(III) complexes in cosmetics like shower cream and foam bath. The non-biodegradable EDTA is used in combination with biodegradable analogues like EDDS and IDS in many commercial products. The HPLC method involves separation by reversed-phase ion pair chromatography on a C₁₈ column using methanol-formate buffer (20 mM tetrabutylammonium hydrogen sulfate, 15 mM sodium formate adjusted to pH 4.0 with formic acid) (10:90, v/v) as mobile solvent at a flow rate of 0.8 mL min⁻¹ at 24 °C using UV detection at 240 nm. The CE separation was performed in a fused silica capillary of 50 μm i.d. with the total length of 50 cm with a 10 mM MES and MOPSO (pH 5.5) at an applied voltage of −25 kV. The samples were introduced by applying a 50 mbar pressure for 2 s. Absorbances at 215 and 225 nm were monitored for the detection of the complexes. The methodology performance of the two methods was evaluated in terms of linearity, limit of detection (LOD), limit of quantitation (LOQ) and reproducibility. The LOD values obtained from HPLC are low when compared with CE. The applicability of both the methods was demonstrated for the analysis of cosmetic products such as shower cream and foam bath. The results obtained by both CE and HPLC were found to be comparable and in good agreement.     

Validation of an online dual-loop cleanup device with an electrospray ionization tandem mass spectrometry-based system for simultaneous quantitative analysis of urinary benzene exposure biomarkers trans, trans-muconic acid and S-phenylmercapturic acid

The aim of this study is to validate isotope-dilution electrospray ionization tandem mass spectrometry (ESI-MS-MS) method with a dual-loop cleanup device for simultaneous quantitation of two benzene metabolites, trans, trans-muconic acid (ttMA) and S-phenylmercapturic acid (SPMA), in human urine. In this study, a pooled blank urine matrix from rural residents was adopted for validation of the analytical method. The calibration curve, detection limit, recovery, precision, accuracy and the stability of sample storage for the system have been characterized. Calibration plots of ttMA and SPMA standards spiked into two kinds of urine matrixes over a wide concentration range, 1/32-8-fold biological exposure indices (BEIs) values, showed good linearity (R > 0.9992). The detection limits in pooled urine matrix for ttMA and SPMA were 1.27 and 0.042 μg g⁻¹ creatinine, respectively. For both of ttMA and SPMA, the intra- and inter-day precision values were considered acceptable well below 25% at the various spiked concentrations. The intra- and inter-day apparent recovery values were also considered acceptable (apparent recovery >90%). The ttMA accuracy was estimated by urinary standard reference material (SRM). The accuracy reported in terms of relative error (RE) was 5.0 ± 2.0% (n = 3). The stability of sample storage at 4 or −20 °C were assessed. Urinary ttMA and SPMA were found to be stable for at least 8 weeks when stored at 4 or −20 °C. In addition, urine samples from different benzene exposure groups were collected and measured in this system. Without tedious manual sample preparation procedure, the analytical system was able to quantify simultaneously ttMA and SPMA in less than 20 min.     

Photoacid generators (PAGs) based on N-acyl-N-phenylhydroxylamines for carboxylic and sulfonic acids

Simple and efficient photoacid generators (PAGs) for carboxylic and sulfonic acids based on N-acyl-N-phenylhydroxylamines have been demonstrated. Irradiation of o-carboxylates and thermally rearranged o-arenesulfonates of N-acyl-N-phenylhydroxylamines using UV light (≥254 nm) in aqueous methanolic solution resulted in efficient generation of carboxylic and sulfonic acids, respectively. The carboxylic acid generation ability of N-acyl-N-phenylhydroxylamines was found to be dependent on their N-acyl substituents. Further, polymer bearing o-arenesulfonates of N-acyl-N-phenylhydroxylamine was synthesized and demonstrated as PAG for sulfonic acids.     

A concise route to (−)-shikimic acid and (−)-5-epi-shikimic acid, and their enantiomers via Barbier reaction and ring-closing metathesis

A simple route for the synthesis of naturally occurring (−)-shikimic acid, (−)-5-epi-shikimic acid, and their enantiomers from d-ribose-derived enantiomeric aldehydes 8a and 8b by employing Barbier reaction and ring-closing metathesis as key steps has been developed.     

The Hammett acidity function H0 in trifluoroacetic acid–dichloromethane mixtures

The acidity function (H₀) of solutions of trifluoroacetic acid (TFA) in dichloromethane was measured by the indicator method at 298 K in the whole concentration range. The H₀ value for the most acidic solution studied (12.93 M trifluoroacetic acid) is −3.09. The equation describing the dependence of H₀ on the acid concentration was determined. The obtained quantitative data were used for a spectrophotometric study of the basicity of 2,9,16,23-tetra-tert-butylphthalocyanine. Two forms with different UV/vis spectra were observed and their stability constants determined.     

The calorimetric investigation of phosphoric acid-N,N-dimethylformamide system

Solution and mixing enthalpies for the orthophosphoric acid (H₃PO₄)-N,N-dimethylformamide (DMF) system were measured over the whole concentration range at 25 °C. The standard value of solution enthalpy of phosphoric acid in DMF and the standard transference enthalpy of H₃PO₄ from water to DMF were calculated. The mixing enthalpy concentration dependence permitted making assumptions on complex formation in the system under investigation.     

A new one-pot synthesis of all E-retinoic acid via a new enaminodiester synthon

A ‘one-pot’ synthesis of allE-retinoic acid from a new enaminodiester was described. The enaminodiester was easily produced from methyl isopropylidenemalonate and DMF-DMA.