Fast analysis of pravastatin in production media Kocijan, Andrej; Grahek, Rok; Bastarda, Andrej ...
Journal of chromatography. B, Analytical technologies in the biomedical and life sciences,
08/2005, Letnik:
822, Številka:
1
Journal Article
Recenzirano
High throughput methods (high performance liquid chromatography and capillary electrophoresis) were developed to determine pravastatin in production media. The analyses were performed on particle ...column, monolithic column and silica capillary filled with borate buffer pH 9.3 containing 20
mM SDS. All three methods successfully separate pravastatin from interfering compounds (matrix, mevastatin and 6-
epi pravastatin) and runtimes are shorter than 1
min. Solvent consumptions for methods using small particle column, monolith column and MECK were 132, 510 and 1.5
mL
h
−1. The most sensitive was the method using particle column (LOD was about 10
−5
mg
mL
−1), followed by the system using monolith column (LOD was 2
×
10
−4
mg
mL
−1) and the MECK method (LOD was about 0.02
mg
mL
−1).
Despite the fact that it was put on the market more than 60 years ago, hydrochlorothiazide (HCT) is still one of the most important antihypertensive drugs. Due to its chemical structure, which ...contains the secondary aryl-alkyl-amino moiety, it is vulnerable to the formation of N-nitrosamine drug substance-related impurity (NDSRI) N-nitroso-hydrochlorothiazide (NO-HCT). In our study, we reveal that NO-HCT degrades rapidly at pH values 6 to 8. The main degradation products identified are formaldehyde, thiatriazine, and aminobenzenesulfonic acid derivative. Interestingly, degradation of NO-HCT at pH values from 5 to 1 is significantly slower and provides a different impurity profile when compared to the profile generated between pH 6 and 8. Specifically, between pH 1 and 5, HCT is observed as one of the key degradation products of NO-HCT in addition to formaldehyde and aminobenzenesulfonic acid. Moreover, at pH 1, the aminobenzenesulfonic acid derivative is transformed to the corresponding diazonium salt in approximately 3% yield with the nitrosyl cation, which is released during the decomposition of NO-HCT to HCT. This diazonium is highly unstable above pH 5. To verify that degradation of NO-HCT does not produce the corresponding diazonium salt that could be formed via metabolic activation of NO-HCT, this diazonium salt and its hydrolytic and reduction degradation products were synthesized and used as standards for the identification of species formed during the degradation of NO-HCT. This enabled us to confirm that the corresponding aryl diazonium salt, which would be obtained from metabolic activation of NO-HCT, is not observed in the NO-HCT degradation pathway. Our study also demonstrates that this diazonium salt is stable only in the presence of a large excess of strong mineral acid under anhydrous conditions. In the presence of water, it is instantaneously converted to an aminobenzenesulfonic acid derivative. These findings suggest that the NO-HCT should not be considered as a typical compound belonging to the cohort of the concern.
Methods were developed for the preparation and isolation of four oxidative degradation products of atorvastatin. ATV-FX1 was prepared in the alkaline acetonitrile solution of atorvastatin with the ...addition of hydrogen peroxide. The exposition of aqueous acetonitrile solution of atorvastatin to sunlight for several hours followed by the alkalization of the solution with potassium hydroxide to pH 8–9 gave ATV-FXA. By the acidification of the solution with phosphoric acid to pH 3 ATV-FXA1 and FXA2 were prepared. The isolation of oxidative degradation products was carried out on a reversed-phase chromatographic column Luna prep C18(2) 10
μm applying several separation steps. The liquid chromatography coupled with a mass spectrometer (LC-MS), high resolution MS (HR-MS), 1D and 2D NMR spectroscopy methods were applied for the structure elucidation. All degradants are due to the oxidation of the pyrrole ring. The most probable reaction mechanism is intermediate endoperoxide formation with subsequent rearrangement and nucleophilic attack by the 5-hydroxy group of the heptanoic fragment. ATV-FX1 is 4-1b-(4-Fluoro-phenyl)-6-hydroxy-6-isopropyl-1a-phenyl-6a-phenylcarbamoyl-hexahydro-1,2-dioxa-5a-aza-cyclopropaainden-3-yl-3-(R)-hydroxy-butyric acid and has a molecular mass increased by two oxygen atoms with regard to atorvastatin. ATV-FXA is the regioisomeric compound, 4-6-(4-Fluoro-phenyl)-6-hydroxy-1b-isopropyl-6a-phenyl-1a-phenylcarbamoyl-hexahydro-1,2-dioxa-5a-aza-cyclopropaainden-3-yl-3-(R)-hydroxy-butyric acid. Its descendants ATV-FXA1 and FXA2 appeared without the atorvastatin heptanoic fragment and are 3-(4-Fluoro-benzoyl)-2-isobutyryl-3-phenyl-oxirane-2-carboxylic acid phenylamide and 4-(4-Fluoro-phenyl)-2,4-dihydroxy-2-isopropyl-5-phenyl-3,6-dioxa-bicyclo3.1.0hexane-1-carboxylic acid phenylamide, respectively. Quantitative NMR spectroscopy was employed for the assay determination of isolated oxidative degradation products. The results obtained were used for the determination of the UV response factors relative to atorvastatin.
A wide variety of pathogens have acquired antimicrobial resistance as an inevitable evolutionary response to the extensive use of antibacterial agents. In particular, one of the most widely used ...antibiotic structural classes is the β-lactams, in which the most common and the most efficient mechanism of bacterial resistance is the synthesis of β-lactamases. Class C β-lactamase enzymes are primarily cephalosporinases, mostly chromosomally encoded, and are inducible by exposure to some β-lactam agents and resistant to inhibition by marketed β-lactamase inhibitors. In an ongoing effort to alleviate this problem a series of novel 4-substituted trinems was designed and synthesized. Significant in vitro inhibitory activity was measured against the bacterial β-lactamases of class C and additionally against class A. The lead compound LK-157 was shown to be a potent mechanism-based inactivator. Acylation of the active site Ser 64 of the class C enzyme β-lactamase was observed in the solved crystal structures of two inhibitors complexes to AmpC enzyme from E. cloacae. Structure−activity relationships in the series reveal the importance of the trinem scaffold for inhibitory activity and the interesting potential of the series for further development.
The enantiomeric resolution and the elution order of (±)-trans-7,8-dihydrodiols of benzoapyrene and its 6-fluoro and 6-bromo derivatives were analyzed on three polysaccharide-based columns: Daicel ...Chiralcel CA-I (cellulose triacetate), OF, and OG cellulose tris(4-chloro- and 4-methylphenylcarbamate). For comparison, the separation of (±)-1,1‘-bi-2-naphthol was evaluated on the OG and OF columns. Possibly similar interactions of (S)-1,1‘-bi-2-naphthol and (7S,8S)-isomers of 6-halo-7,8-dihydroxy-7,8-dihydrobenzoapyrene with the chiral sorbent are suggested.
The chromatographic behaviour of the ACE inhibitors lisinopril, enalapril and its two degradation products, enalaprilat (hydrolytic degradation product) and diketopiperazine (DKP) (cyclization ...degradation product) was studied as a function of column temperature and pH of the mobile phase. The rate of isomerization (which influences the peak shape or even peak splitting during chromatographic analysis) increases with temperature. The shape of the chromatographic peak for enalapril, enalaprilat and lisinopril is also pH dependent. At high temperature (80°C) and low pH (pH=2) all studied compounds appear on the chromatogram as a narrow chromatographic peak. Chromatographic peaks become broader or they split by lowering the column temperature. Enalapril appears at 6°C on the chromatogram in two peaks which belong to its
cis- and
trans-rotation isomers. Separation of the rotamers was confirmed by NMR spectroscopy.
