Drugs online research references
ismailia.ie-eg.com
Different spectrophotometric and HPTLC-densitometric methods are presented for the simultaneous determination of lisinopril and hydrochlorothiazide in pharmaceutical tablets. The spectrophotometric methods include third derivative (3D) ultraviolet spectrophotometry with zero crossing measurement at 217.4 and 233.4 nm, second derivative of the ratio spectra with measurement at 214.3 and 228.0 nm; both classical least squares and principal component regression were applied to the UV absorption and first derivative spectra of the mixture. The HPTLC method was based on separation of both drugs followed by densitometric measurements of their spots at 210 and 275 nm for lisinopril and hydrochlorothiazide, respectively. The separation was carried out on Merck HPTLC aluminum plates of silica gel 60 F254, using chloroform-ethylacetate-acetic acid (10:3:2 by vol.) as mobile phase. The linear and second order polynomial were used for the regression equation of lisinopril and hydrochlorothiazide, respectively.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11377075&dopt=Abstract
lek.si
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 degrees 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 degrees 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.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11393708&dopt=Abstract
Biochemistry (Mosc). 2001 Apr;66(4):429-34.
Characterization of bovine atrial angiotensin-converting enzyme.
Garats EV, Nikolskaya II, Binevski PV, Pozdnev VF, Kost OA.
School of Chemistry, Lomonosov Moscow State University, Moscow, 119899, Russia.
Bovine atrial angiotensin-converting enzyme (ACE) was purified to electrophoretic homogeneity. The purification procedure included ion-exchange chromatography on DEAE-Toyopearl 650M, affinity chromatography on lisinopril-agarose and gel filtration on Sephadex G-100. The bovine atrial ACE exhibited similar sensitivities to inhibition by lisinopril and captopril as lung ACE (the Ki values for the atrial and lung enzymes differed insignificantly). However, the kinetic parameters of hydrolysis of some synthetic tripeptide substrates (FA-Phe-Gly-Gly, FA-Phe-Phe-Arg, Cbz-Phe-His-Leu, Hip-His-Leu) catalyzed by bovine atrial and lung ACE varied to a greater extent. The enzymes were also characterized by some differences in activation by chloride, nitrate, and sulfate anions. These data support the hypothesis of tissue specificity of ACEs.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11403651&dopt=Abstract
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