Production and Characterization of Monoclonal Antibodies Recognizing the Asymmetric Center of Optically Active Bufuralol and Its Metabolites

Abstract

The chromatographic determination of enantiomeric drugs and the metabolites in biological fluids is one of the most important subjects in biomedical analysis, because the individual isomers exhibit different pharmacological properties as well as pharmacokinetic and metabolic fates.Bufuralol, 1-(7-ethylbenzofuran-2-yl)-2-t-butylamino-1-hydroxyethane, is a nonselective β-adrenergic receptor antagonist 1 with partial β2-agonist properties 2,3 and is administered as the racemic form. The β-blocking potency of (1S)-bufuralol is approximately 100 times greater than that of the (1R)-enantiomer. 4 The metabolism of bufuralol is complex; many metabolites are formed, 5 differential metabolism between the two enantiomers occurs, 6 and differences due to genetic polymorphism are also encountered. 7 Nevertheless, the metabolites, diastereomeric carbinols and enatiomeric ketones, both of which are present to a large extent in a biological fluid, also have pharmacological activity 8 comparable to the parent drug. Therefore, a reliable method for the simultaneous determination of enantiomeric bufuralol along with its metabolites is essential for pharmacokinetic and pharmacodynamic studies.Various chromatographic methods are now available for the separation and determination of enantiomers. The analytical procedure includes the use of a chiral chromatographic mode based on either chiral stationary phases or chiral eluents, and the use of a derivatization technique with a chiral reagent to produce the diastereomers, which are easily separated with a conventional separation column. [9][10][11][12][13] There are a number of chiral reagents having a reacting group to form a covalent bond with target analytes and a signal group highly responsive to a detector. 14 The reaction should proceed completely without any racemization. This method, although it is favorable for obtaining higher sensitivity, has disadvantages due to the tedious derivatization process and a clean-up procedure to remove excess reagents. Moreover, it has been shown that enantiomers can react with a chiral reagent at very different rates. 15High-performance liquid chromatography (HPLC) employing chiral stationary phases is well recognized as a powerful tool for the direct separation of racemates. A wide variety of separation columns including the Pirkle-type, cyclodextrin-bonded, various cellulose-based, and immobilized protein columns have been developed and are commercially available.In recent years, immunoaffinity chromatography (IAC) based on specific and reversible antigen-antibody reactions 16 has been shown to be capable of separating and determining a number of different analytes and to be a powerful analytical or pretreatment tool in biomedical analysis. In our previous study, rabbit polyclonal antibodies with high specificity for an essential chirality center have been prepared for the enantiomeric immunoaffinity extraction of optically active bufuralol and its 1′-oxidized metabolites. 17 However, it is difficult to obtain conventional polyclonal antibodi...

The Enantioselective Immunoaffinity Extraction of an Optically Active Ibuprofen-Modified Peptide Fragment

“…The immunosorbent we have described may also be applied to the group extraction of (S)-enantiomers of ibuprofen and its metabolites such as taurine conjugate and acyl glucuronide from biological fluids prior to the chromatographic determination of target compounds. In a previous paper, we disclosed the utility of a monoclonal antibody for the immunohistochemical extraction of optical active bufuralol and its metabolites (33). Production of a monoclonal antibody utilizing the same immunogenic conjugate is our next end.…”