Stereoselective Inhibition of Human Butyrylcholinesterase by the Enantiomers of Bambuterol and Their Intermediates
作者:Marco Pistolozzi、Huaqiao Du、Hong Wei、Wen Tan
DOI:10.1124/dmd.114.060251
日期:2015.3
This work describes the sequential hydrolysis of bambuterol enantiomers and their monocarbamate metabolites (MONO) catalyzed by human butyrylcholinesterase (BChE) as well as the enzyme inhibition resulting from this process. Particular emphasis is given to the contribution given by MONO to the enzyme inhibition because it was not fully characterized in previous works. Bambuterol and MONO enantiomers displayed the same time- and concentration-dependent mechanism of interaction with the enzyme. The hydrolysis kinetics of both bambuterol and MONO was enantioselective, and the (R)-enantiomer of each compound was hydrolyzed fourfold faster than the respective (S)-enantiomer. Even though the enzyme inhibition rates of (R)- and (S)-MONO were much slower than those of their respective bambuterol enantiomers (∼15-fold), both MONO enantiomers showed a significant BChE inhibition when physiologically relevant concentrations of enzyme and inhibitors were used (∼50% of their respective bambuterol enantiomers). The kinetic constants obtained by testing each single compound were used to model the contribution given by MONO to the enzyme inhibition observed for bambuterol. The hydrolysis of MONO enantiomers enhanced the inhibitory power of bambuterol enantiomers of about 27.5% (R) and 12.5% (S) and extended more than 1 hour the duration of inhibition. The data indicate that MONO contribute significantly to the inhibition of BChE occurring in humans upon administration of normal doses of bambuterol. In addition, the hydrolysis of MONO resulted in the rate-limiting step in the conversion of bambuterol in its pharmacologically active metabolite terbutaline; therefore, MONO concentrations should always be monitored during pharmacokinetic studies of bambuterol.
Resolution of Rac-Bambuterol via Diastereoisomeric Salt Formation with o-Chloromandelic Acid and Differences in the Enantiomers' Pharmacodynamical Effects in Guinea Pigs and Beagles
作者:Jie Wu、Fei Liu、Shanping Wang、Hongjun Wang、Qing Liu、Xinghan Song、Junxiao Li、Ling Xu、Wen Tan
DOI:10.1002/chir.22573
日期:2016.4
reverse‐phase HPLC analyses, respectively. The ee values and the chemical purities both exceeded 99%. Animal experiments showed that (R)‐bambuterol was a potent inhibitor for histamine‐induced asthma reactions. (S)‐bambuterol was ineffective in relaxing the airways. Both enantiomers increased heart rates in beagles. Therefore, replacing rac‐bambuterol with (R)‐bambuterol could be beneficial for asthma