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  • Articles: DFG German National Licenses  (4)
  • antimalarial agents  (2)
  • enantioselective  (2)
  • 1
    ISSN: 0899-0042
    Keywords: stereoselective excretion ; enantioselective ; chromatography ; assay validation ; hydroxychloroquine metabolism ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A sequential achiral-chiral high-performance liquid chromatographic system has been developed for the quantitation in urine of the enantiomers of hydroxychloroquine (HCQ), and of its 3 major metabolites, desethylhydroxychloroquine (DHCQ), desethylchloroquine (DCQ), and bisdesethylchloroquine (BDCQ). HCQ and its metabolites were separated and quantified on a cyano-bonded phase, and the enantiomeric ratios were determined using a Chiral-AGP chiral stationary phase. The assay validation and application of this method to a preliminary study in a human volunteer are presented. In this subject, the initial 0-4 h urine contained the 2 HCQ enantiomers in a ratio of (+)-HCQ:(-)-HCQ of 3:2; by the 2,064 h of the study, this ratio had reversed to (+)-HCQ:(-)-HCQ of 3:7. © 1993 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 5 (1993), S. 84-90 
    ISSN: 0899-0042
    Keywords: in vitro dissolution ; enantioselective ; enantiomers ; bioequivalency ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The stereoselectivity of the in vitro dissolution of two commercially available sustained release formulations of rac-verapamil (rac-VER) has been investigated. The studies were carried out using a single-tablet continuous-flow apparatus and the concentrations of R- and S-VER released from the formulations were measured using enantioselective chromatography on a high performance liquid chromatography (HPLC) chiral stationary phase containing immobilized α1-acid glycoprotein (Chiral AGP-column). The data from this study demonstrates that the two formulations have different dissolution profiles and that the amount of drug dissolved was highly dependent on pH. In addition, between pH 3 and 8, the total cumulative amount of R-VER released was greater than the amount of S-VER and a statistically significant difference (P 〈 0.01) was detected at pH 6. The results of this study indicate that bioavailability and bioequivalency studies should consider the possibility of enantioselective dissolution when racemic compounds are present in the formulations. © 1993 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0899-0042
    Keywords: (S)-naphthylurea chiral stationary phase ; subcritical fluid chromatography ; supercritical fluid chromatography ; antimalarial agents ; enantiomeric separations ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The behavior of mefloquine, halofantrine, enpiroline, quinine, quinidine, chloroquine and primaquine is studied by subcritical fluid chromatography on a (S)-naphthylurea column (250 mm × 4.6 mm ID) with a subcritical mobile phase composed of carbon dioxide, methanol and triethylamine (flow rate of 3 ml/min). Except for primaquine and chloroquine, each enantiomer was separated at a temperature between 40 and 60°C, and at a pressure below 15 MPa. A 98/2, v/v CO2/methanol 0.1% triethylamine mixture allowed the separation of halofantrine enantiomers while the enantiomers of the more polar metabolite (N-desbutylhalofantrine) were separated with a 80-20 v/v mixture as used for mefloquine, enpiroline, quinine and quinidine. The influence of temperature, pressure and of the nature of the mobile phase is discussed. © 1993 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0899-0042
    Keywords: chiral liquid chromatography ; α1 -acid glycoprotein ; antimalarial agents ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of mobile phase pH and dimethyloctylamine (DMOA) on the retention (k') and stereoselectivity (α) of antimalarial agents mefloquine, enpiroline, and chloroquine on the α1-acid glycoprotein chiral stationary phase (AGP-CSP) was investigated. An increase of k' with increasing pH was observed while the effect on α was a function of the solute. The magnitude and direction of changes induced by DMOA depended on pH and the structure of the solute.The results of this study are consistent with a change of the conformation of the AGP between pH 5 and 7. At pH 7, the effect of DMOA on mefloquine was relatively well described by a competitive displacement from one enantioselective site. The effect on chloroquine and enpiroline suggests a multiple-site mechanism in which both competitive and allosteric interactions are involved.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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