Abstract
A new HPLC method was developed using a chiral column to efficiently separate four 1′′-hydroxybufuralol (1′′-OH-BF) diastereomers that are major metabolites of bufuralol (BF). Employing this method, we examined diastereomer selectivity in the formation of 1′′-OH-BF from BF racemate or enantiomers in four individual samples of human liver microsomes. Three different human liver microsomes showed a selectivity of 1′′R-OH < 1′′S-OH for BF enantiomers, which was similar to that of recombinant CYP2D6 expressed in insect cell microsomes, whereas one human liver microsomal fraction yielded a selectivity of 1′′R-OH > 1′′S-OH for BF enantiomers, which was similar to those of recombinant CYP2C19 expressed in insect cell microsomes. Recombinant CYP1A2 and CYP3A4 showed a selectivity similar to that of CYP2D6, but their BF 1′′-hydroxylase activities were much lower than those of CYP2D6. In inhibition studies, quinidine, a known CYP2D6 inhibitor, markedly inhibited BF 1′′-hydroxylation in the fractions of human liver microsomes that showed the CYP2D6-type selectivity. Furthermore, omeprazole, a known CYP2C19 inhibitor, efficiently suppressed the formation of 1′′-OH-BF diastereomers from BF in the microsomal fraction that showed the CYP2C19-type selectivity. From these results, we concluded that the diastereomer selectivity in the formation of 1′′-OH-BF from BF differs between CYP2D6 and CYP2C19, both of which can be determinant enzymes in the diastereoselective 1′′-hydroxylation of BF in human liver microsomes.
Footnotes
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DOI: 10.1124/jpet.102.036533
- Abbreviations:
- CYP
- cytochrome P450
- BF
- bufuralol
- R-BF
- 1′R-OH-bufuralol
- S-BF
- 1′S-OH-bufuralol
- 1′′R-OH-R-BF
- 1′′R-OH-1′R-bufuralol
- 1′′S-OH-R-BF
- 1′′S-OH-1′R-bufuralol
- 1′′R-OH-S-BF
- 1′′R-OH-1′S-bufuralol
- 1′′S-OH-S-BF
- 1′′S-OH-1′S-bufuralol
- BTL
- bunitrolol
- DB
- debrisoquine
- 4-OH-DB
- 4-hydroxydebrisoquine
- G-6-P
- glucose 6-phosphate
- Received March 20, 2002.
- Accepted May 28, 2002.
- The American Society for Pharmacology and Experimental Therapeutics
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