化妆品中甲氧基补骨脂素同分异构体的液相色谱法分离和测定

建立了用高效液相色谱(HPLC)-二极管阵列检测器(DAD)测定化妆品中两种呋喃香豆素同分异构体-8-甲氧基补骨脂素(8-MOP)和5-甲氧基补骨脂素(5-MOP)的简便方法。样品用甲醇超声提取,高速冷冻离心,经0.45μm滤膜过滤,注入高效液相色谱,用DAD进行扫描检测,并在301 nm波长进行分析。用保留时间结合紫外光谱图定性,外标法定量,并且采用液质联用(LC/MS/MS)确证。测试结果对8-MOP的回收率为87.0%~105.0%,RSD为0.41%~5.3%,检出限为5.0 mg/kg;5-MOP的回收率为88.0%~105.0%,RSD为0.33%~4.1%,检出限为5.0 mg/kg。本文用DAD同时分离和检测了化妆品中的8-MOP和5-MOP,方法可用于化妆品安全性监控。     

Quantitative measurement of isomeric cyclic nucleotides from T-lymphocytes by HPLC

Summary The influence of thymic factors on the levels of different cyclic nucleotides in human lymphoblastic lymphoma cells has been studied. A single-step HPLC method for the simultaneous determination of 2,3-cGMP, 3,5-cGMP, 2,3-cAMP and 3,5-cAMP from biological cell materials is described. Concentrations even in the picomolar range could be determined quantitatively.

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Quantitative HPLC-Messung isomerer cyclischer Nucleotide aus T-Lymphocyten

     

NMR studies of the configuration of the isomeric 2,3-dimethyloxetanes

The ¹H and ¹³C NMR spectra of cis- and trans-2,3-dimethyloxetane have been re-examined and the published NMR assignments shown to be in error.     

Assignment of isomeric hydroxyhydantoins: Linked-scan,tandem and high-resolution studies

The mass spectral fragmentation of hydroxyhydantoins was studied by a combination of high-resolution, linked-scan and collisionally activated decomposition (CAD) experiments. This endeavor resulted in the structural assignment of four pairs of synthetic hydroxyhydantoin isomers. A key feature in differentiating l-methyl-3- aryl-5-hydroxy-2,4-imidazolidinediones from 1-aryl-3-methyl-5-hydroxy-2,4-imidazolidinediones is that under electron ionizarion (EI) conditions only the 1-methyl-3-aryl-5-hydroxy-2,4-imidazolidinediones yield the [MeNHCHO]⁺˙ ion. The analogous [ArNHCHO]⁺˙ ion (where Ar is the aryl group) was present in the EI spectra of both isomers and its origins are explained by the linked-scan and CAD experiments performed.     

Heterocyclic studies: New heterocyclic ring systems from isomeric dimethyl diaminophthalates

The synthesis and reactions of dimethyl 3, 4- and 4, 5-diaminophthalate 7 and 9 were investigated. The condensation of these isomeric diaminophthalates and their respective nitroacetamido precursors have been shown to give rise to a variety of five, six and seven membered heterocyclic ring system. Several new tetraazanthracenes have also been prepared in this sequence.     

Drug metabolism studies using HPLC

Summary The analyses of the plasma concentrations of two drugs, one a water soluble weak base and the other a lipophilic ester with acidic metabolites, are used to illustrate the advantages of reversed-phase chromatography over other techniques in drug metabolism studies. The problems associated with each method are discussed and compared.     

Analysis of isomeric glutamyl peptides by capillary electrophoresis. Application to stability studies

Capillary electrophoresis has been used for the separation of the glutamyl tripeptides Gly-alpha-Glu-Phe-NH2 and Phe-alpha-Glu-Gly-NH2 including their potential degradation and isomerization products Gly-gamma-Glu-Phe-NH2, alpha-Glu-Phe-NH2, gamma-Glu-Phe-NH2 and Phe-NH2 as well as Phe-gamma-Glu-Gly-NH2, Phe-Glu and Phe, respectively. Between pH 2.2 and pH 10.0 the effective mobilities of the glutamyl peptides have been investigated. Using histidine hydrochloride as internal standard at pH 2.2 linear calibration curves for both assays were obtained for a concentration range from 10 microg ml(-1) to 3.5 mg ml(-1). The assay was applied to analyze the degradation of the tripeptides in solution at pH 7 and pH 3 at 70 degrees C. Hydrolysis and isomerization of the glutamyl peptides were found in the incubation mixtures.     

HPLC in pharmacokinetics and metabolism studies

Summary The use of high-performance liquid chromatography in kinetics and metabolism studies is demonstrated.The following kinetic parameters are ascertained after single oral and intravenous administration of a drug: absorption by areal comparison, elimination constant in the -phase, and clearance.Concentration levels in serum are measured after repeated oral administration on several days, with pharmacokinetic model fit to estimate limit concentrations in the steady state. Species-dependencies in metabolism are investigated in 24-h urines.The necessary characterization of drug and metabolite peaks is obtained by in-series connection of several detectors.The relative bioavailability of a controlled release form is determined by measuring drug concentrations in the blood.     

1H and 13C NMR studies of the protonation of isomeric methoxysulmazole analogues

The major protonation sites of six cardiotonic isomeric 2-aryl-n-methoxy-1H-imidazo[4,5-b]- and -[4,5-c]-pyridines (n = 4–7) were determined by ¹H and ¹³C NMR methods. All the 1H-imidazo[4,5-c]pyridines and the 7-methoxy derivative of sulmazole were found to protonate at the pyridyl nitrogen. Protonation occurred at the imidazo nitrogen, however, for the 5- and 6-methoxy derivatives of sulmazole.     

Calculations of 1H NMR coupling constants for conformational studies of isomeric pentofuranosyl nucleosides

The SCF FPT method in the INDO approximation of molecular orbital theory is employed for calculations of ¹H NMR cisoidal coupling constants in model compounds. Obtained results are used for finding conformational states of α-xylo-, β-lyxo-, and α-2′-deoxyribonucleosides in solution.     

Fast-atom bombardment mass spectrometry and metastable-ion studies for the characterization of isomeric fluorosugars.

Characterization of stereoisomeric 3,4-dideoxy-3-fluoro-hexoses has been carried out using fast-atom bombardment. Diagnostic fragments were observed in the daughter-ion spectra of the [M - H]- and [M + H]+ ionic species. Notable differences were also observed in the relative abundances of ionic species corresponding to [M - H]-, [M - H - HF]- and [C11H11O2]- ions.     

Isomerization studies—I : Conversion of linear acids into their isomeric branched-chain analogues

The transformation of linear saturated carboxylic acid chlorides (i.e., stearoyl chloride) into mixtures of isomeric, highly branched acids, each having the same molecular weight as the starting material, was investigated. The fatty acid backbone was modified in either a two or three step process generally with excellent overall yield. In both procedures, the first step was catalytic decarbonylation of the acid chloride, which yielded a hydrocarbon monoene mixture having one less carbon atom than the starting acid. The monoene mixtures were reconverted to the branched acid derivatives by either the Koch reaction or the hydroformylation oxidative procedure. Products were designated as either dior trisubstituted carboxylic acids, on the basis of mass spectroscopic and GLC data.     

Surface tensions for isomeric chlorobutanes with isomeric butanols

A drop volume tensiometer was employed to measure the surface tensions for the binary mixtures of each of the isomers of chlorobutane with each of the isomers of butanol at a temperature of 298.15 K. From these data the surface tension deviations were calculated. The results have been compared with the predictions obtained by the group contribution method proposed by Suarez.     

13C NMR studies of isomeric piperidine derivatives with opiate properties and related compounds

The ¹³C NMR spectra of a series of methyl substituted 3-arylpiperidines and 4-aryl-4-piperidinols and related compounds are reported, and chemical shift data analysed in terms of the configuration and conformation of isomeric pairs. Special attention is given to the γ chemical shift parameter of axial methyl, and the effects of a nitrogen lone pair orbital and hydroxyl or acyloxy group on the chemical shifts of ring and methyl carbons.     

Chromatographic and mass spectral studies on isobaric and isomeric substances related to 3,4-methylenedioxymethamphetamine

A series of isobaric and isomeric molecules related to 3,4methylenedioxymethamphetamine (3,4-MDMA) are prepared and evaluated as potential mass spectral equivalents to this controlled substance. These compounds have the potential to produce a mass spectrum equivalent to 3,4-MDMA, thus making mass spectrometry a nonconclusive method for confirming the identity of any one of the substances. The various isomeric forms of the methoxymethylphenethylamines and the methoxymethcathinones have mass spectra essentially equivalent to 3,4-MDMA, but the ethoxy substituted phenethylamines show a unique fragment at m/z 107. Gas chromatographic separation on nonpolar stationary phases successfully resolved these compounds from 3,4-MDMA, however only a limited set of side chain regioisomers and ring substitution patterns are evaluated in this initial study.     

Thermodegradation of isomeric polybutylmethacrylates

The thermodegradation of polybutylmethacrylates synthesized from all four isomers of butyl methacrylate has been investigated by TG and DTA methods in oxidative, inert and self-generating atmospheres. It was established that the influence of the atmosphere surrounding the polymer on the temperature characteristics of the samples depends on the degree of branching of the substituents in the polybutylmethacrylate (PBMA). It is assumed that the difference in thermodegradation of isomeric polybutylmethacrylates is related to the difference in the degree of substitution of the α-carbon in the ester substituent.     

Synthesis of isomeric triazolopyrrolopyrimidines

4‐Hydrazino‐7H‐pyrrolo[2,3‐d]pyrimidines ( 4 ) were cyclocondensed with formic acid or triethyl orthoformate to give 7H‐1,2,4‐triazolo[1,5‐c]pyrrolo[3,2‐e]pyrimidines ( 5 ) and 7H‐1,2,4‐triazolo[4,3‐c]pyrrolo‐[3,2‐e]pyrimidines ( 6 ) respectively. The [4,3‐c]‐isomers ( 6 ) were rearranged into thermodynamically more stable [1,5‐c]‐isomers ( 5 ). The identical compounds ( 5 ) were prepared using another route by reacting 3‐amino‐4‐imino‐7H‐pyrrolo[2,3‐d]pyrimidines ( 3 ) with formic acid or triethylorthoformate. Reaction of 2‐amino‐3‐cyanopyrroles ( 1 ) with triethyl orthoformate followed by hydrazinolysis afforded ( 3 ) via the formation of N‐ethoxymethylene‐2‐amino‐3‐cyanopyrroles ( 2 ).