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  • 1
    Electronic Resource
    Electronic Resource
    Pharmacokinetic studies with the lipid-regulating agent beclobrate: Enantiospecific assay for beclobric acid using a new fluorescent chiral coupling component (S-FLOPA) (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 35-42 
    Details
    ISSN: 0899-0042
    Keywords: chiral derivatization ; pharmacokinetics ; enantiospecific assay ; fluorescent derivatization ; flunoxaprofen ; acyl glucuronides ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The major biotransformation pathway for the chiral lipid-regulating agent beclobrate is conversion to the corresponding carboxylic acid, which is then metabolized to the acyl glucuronide. An enantiospecific assay for biological material was developed that is based on chiral derivatization with N-ethyl-N′-(3-dimethylaminopropyl)carbodiimide (EDAC) and the primary amine S-FLOPA, a new chiral coupling component for carboxylic acids derived from the 2-arylpropionic acid S-flunoxaprofen. Conversion of beclobric acid to the acyl chloride prior to coupling with the amine is also feasible. From plasma or urine beclobric acid was extracted into n-hexane/ethanol (9:1) at pH 4 after addition of sodium chloride. Clofibric acid was used as internal standard. Derivatization with EDAC/FLOPA was performed under addition of 1-hydroxybenzotriazole in anhydrous dichloromethane containing trace amounts of pyridine (ambient temperature/2 h reaction time). The chromatographic separation was performed on a silica gel stationary phase (Zorbax Sil) using n-hexane-chloroform-ethanol (100:10: 0.75, by vol) as mobile phase [flow rate, 2 ml/min; fluorescence detection, 305/355 nm; elution order of the derivatives, (-) before (+)]. Coefficients of variation were between 1.3 and 9.3% for both plasma and urine. Limit of quantification was 20-25 ng/ml for plasma based on a sample volume of 0.2 ml. Application of the assay in a pilot pharmacokinetic study showed significant differences between the kinetics of the two enantiomers. In plasma and urine, the concentrations of the dextrorotatory enantiomer exceeded those of the levorotatory enantiomer significantly.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530030108
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  • 2
    Electronic Resource
    Electronic Resource
    In vitro and in vivo irreversible plasma protein binding of beclobric acid enantiomers (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 5 (1993), S. 120-125 
    Details
    ISSN: 0899-0042
    Keywords: beclobrate ; beclobric acid ; acyl glucuronides ; hydrolysis ; isomerization ; irreversible binding ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Acyl glucuronides are known to be labile conjugates, which undergo hydrolysis and bind irreversibly to proteins. The lipid-regulating agent (±)-beclobrate is immediately converted to the free acid after oral administration. Further metabolism leads to formation of the corresponding diastereomeric acyl glucuronides. Beclobric acid glucuronides were quantified by indirect measurement with an HPLC method based on chiral fluorescent derivatization of the carboxylic acid and subsequent normal-phase chromatography. The renal clearance of unchanged drug is low, with almost all drug excreted into urine as glucuronic acid conjugates. Beclobric acid glucuronide is also detectable in plasma. In vitro degradation studies with beclobric acid glucuronide (at a concentration of 5 μM in 150 mM phosphate buffer pH 7.4) exhibited a minor tendency for acyl migration and hydrolysis, i.e., a higher stability than has been observed for the acyl glucuronides of most other drugs. The in vitro degradation half-lives of the two beclobric acid β-1-O-acyl glucuronides were 22.7 and 25.7 h. After incubation with pooled plasma and human serum albumin in buffer pH 7.4 irreversible binding was measured in vitro. No significant difference between the two enantiomers was detected with respect to the magnitude of in vitro irreversible binding. In 3 healthy male volunteers the extent of irreversible binding of both beclobric acid enantiomers to plasma proteins was investigated after single and multiple oral doses of racemic beclobrate (100 mg once daily). Irreversible binding of both enantiomers was observed in all volunteers. The adduct densities for (-)- and (+)-beclobric acid after single 100 mg beclobrate doses were 0.147 × 10-4 and 0.177 × 10-4 mol/mol protein. Multipie dosing increased irreversible binding 3- to 4-fold. © 1993 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530050304
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    Paper (German National Licenses)
    Fulltext
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