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991.
Summary The performance of two chromatographic (HPLC) methods recommended for hydrophobicity evaluation of structurally diverse (noncongeneric)
solutes was compared. Azole derivative drugs possessing properties of weak organic bases were used as the test solutes. One
of the methods, recommended by Minick and co-workers, consists on suppressing specific interactions with the stationary phase
(ODS) by adding modifiers to the eluent of neutral pH. The other method, developed previously in our laboratory, yields retention
data for nonionized bases due to using poly(butadiene)-coated alumina (PBCA) columns which can be operated under alkaline
conditions. It has been demonstrated that in the case of basic solutes, hydrophobicity parameters obtained by the method employing
PBCA columns are more reliable. The noncontrolled specific interactions of organic bases with the ODS phase at pH 7.0 remain
effective in spite of special precautions undertaken. 相似文献
992.
Maria Luiza C. Montanari Adriano D. Andricopulo Carlos A. Montanari 《Analytica chimica acta》2005,545(1):33-45
Chiral sulfoxide drugs such as omeprazole, lansoprazole and pantoprazole were chromatographed on three chiral stationary phases (CSP), using amylose tris-(phenylcarbamate) derivatives in the reversed-phase mode. The retention factors (k) and chromatographic partition coefficients (kw), obtained by extrapolation of the first according to the linear Snyder equation, were analyzed employing molecular interaction fields (MIF) of eluted analytes. Based on the generated MIF, chiral selectors could be identified for improving enantiomeric separation performance of the respective sulfoxides. The method is useful for predicting the complementarities between CSP and analytes, and thus to help the selection of appropriate stationary phases prior to their preparation. 相似文献
993.
The review is devoted to the problems related to inhibition of the generation of nitric oxide, a versatile regulator of cell metabolism, whose excessive production is responsible for various pathologies. The approaches to the preparation of inhibitors are discussed and the prospects for the synthesis of inhibitors selective with respect to various NO-synthase isoforms are considered; these aspects largely determine the possibility of using these compounds in medicine. The structures of some classes of inhibitors are presented and their biological properties and the main applications for arresting pathological states are discussed. 相似文献
994.
995.
Marciniec B. Kozak M. Ogrodowczyk M. 《Journal of Thermal Analysis and Calorimetry》2004,77(2):581-596
The effect of sterilisation by irradiation has been studied for the seven most often used in medicine derivatives of 1,4-dihydropyridine
(nifedipine, nisoldipine, nicardipine, nitrendipine, nimodipine, felodipine and amlodipine). The sterilisation was performed
for the compounds in the solid phase with an electron beam of the energy 10 MeV, at room temperature, using the irradiation
doses from 20 to 400 kGy. The effects of the irradiation were studied by the methods SEM, DSC, XRD and TLC. The sterilisation
with doses 20-100 kGy was found to cause no changes in the physico-chemical properties of the compounds, while the irradiation
with higher doses (200-400 kGy) was found to induce changes in the colour, DSC spectrum and TLC picture. As follows from the
TLC results, the main product of radiolysis of the compounds studied was a pyridine nitrozoderivative, which indicates the
same mechanism of decomposition as in the process of photodegradation. The results prove that the 1,4-dihydropyridine derivatives
being highly sensitive to visible and UV radiation are generally resistant to ionising radiation and thus can be subjected
to sterilisation by irradiation.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
996.
A high-performance liquid chromatographic (HPLC) method is described for the simultaneous determination of sophoridine and matrine in rat plasma. Sophoridine and matrine in the resulting supernatant of the plasma deproteinized with acetonitrile containing an internal standard (acetanilide) were directly determined by reversed-phase HPLC and ultraviolet detection. The result of limits of quantitation for matrine and sophoridine were 200 and 350 ng/mL in plasma, respectively, and recovery of both analytes was greater than 98%. The assay was linear from 250 to 4000 ng/mL for matrine and from 500 to 8000 ng/mL for sophoridine. Variation over the range of the standard curve was less than 15%. The method was used to determine the concentration-time profiles of matrine and sophoridine in the plasma following oral administration of Kexieling tablets, which is one of the preparations of Kudouzi at a dose equivalent to 30 and 60 mg/kg of matrine and sophoridine, respectively. 相似文献
997.
Summary Ultrahigh pressure liquid chromatography was demonstrated for fast and efficient chiral separations. Capillary columns approximately
13–24 cm in length packed with nonporous 1.0μm C6-modified silical particles were used. β-Cyclodextrin (β-CD) and 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) were added to the
mobile phase as modifiers to produce transient diastereomeric complexes with the analytes. Pressures up to ≈42,000 psi were
applied, and efficiencies in excess of 200,000 plates m−1 were obtained for separations that were accomplished in less than 2 minutes. 相似文献
998.
β-Blocking drugs present in commercial pharmaceutical products are determined in present urine of volunteers between 4 and 24 hours after the administration of a therapeutical dose. The drugs are extracted, hydrolysed, derivatized with pentafluoropropionic anhydride, and analyzed by capillary gas chromatography and electron capture detection. Metabolite identification and drug confirmation is by capillary gas chromatography–negative ion chemical ionization mass spectrometry (GC-NICIMS). This method is very specific and a sensitivity below 1 ng/ml is obtained. 相似文献
999.
Simultaneous determination of two antidiabetic drugs, metformin and glyburide, in pharmaceutical tablet formulations were investigated. Normal phase thin layer chromatography plate (silica gel 60 F254) was used as stationary phase and water/methanol/ammonium sulfate (2/1/0.5 w/v) as mobile phase to determine two pharmaceutically active ingredients, in three different formulations of Glucovance®. This system gave a good resolution for metformin (R f value of 0.43 ± 0.01) and glyburide (R f value of 0.64 ± 0.02). Determination was by densitometry in the absorbance mode at 237 nm. The linear regression data for the calibration plot showed a good relationship with r = 0.99581 and 0.99982 for metformin and glyburide, respectively. The method was validated for precision and recovery. The limits of detection and quantification were 25.24 and 84.12 ng spot?1 for metformin and 12.26 and 40.86 ng spot?1 for glyburide, respectively. Stability study has been carried out for samples and standard solutions. 相似文献
1000.
A mild and highly efficient synthesis of C7-C14 and C15-C21 fragments of epothilone B and D is described in which racemic C7-C14 fragment is prepared from nerol through four steps and C15-C21 fragment is obtained from 1,3-dichloroacctone.thioacetamide and propionaldehyde. 相似文献